Better error message when an msgstr string is an invalid format string.

20 files changed, 879 insertions, 217 deletions

diff --git a/gettext-tools/po/ChangeLog b/gettext-tools/po/ChangeLog
index 5a929fc..841ddd6 100644
--- a/gettext-tools/po/ChangeLog
+++ b/gettext-tools/po/ChangeLog
@@ -1,3 +1,8 @@
+2003-02-23  Bruno Haible  <bruno@clisp.org>
+
+	* POTFILES.in: Add src/format-invalid.h. Replace src/po-gram-gen.c
+	with src/po-gram-gen.y.
+
 2003-02-16  Bruno Haible  <bruno@clisp.org>
 
 	* Makevars.template: New file.
diff --git a/gettext-tools/po/POTFILES.in b/gettext-tools/po/POTFILES.in
index 46ae65a..787a1d1 100644
--- a/gettext-tools/po/POTFILES.in
+++ b/gettext-tools/po/POTFILES.in
@@ -26,6 +26,7 @@ src/file-list.c
 src/format-awk.c
 src/format-c.c
 src/format-elisp.c
+src/format-invalid.h
 src/format-java.c
 src/format-librep.c
 src/format-lisp.c
@@ -54,7 +55,7 @@ src/msgunfmt.c
 src/msguniq.c
 src/open-po.c
 src/po-charset.c
-src/po-gram-gen.c
+src/po-gram-gen.y
 src/po-lex.h
 src/po-lex.c
 src/read-java.c
diff --git a/gettext-tools/src/ChangeLog b/gettext-tools/src/ChangeLog
index 439703e..2fba9b5 100644
--- a/gettext-tools/src/ChangeLog
+++ b/gettext-tools/src/ChangeLog
@@ -1,3 +1,44 @@
+2003-02-23  Bruno Haible  <bruno@clisp.org>
+
+	Improve error messages for invalid format strings.
+	* format-invalid.h: New file.
+	* format.h (struct formatstring_parser): Add invalid_reason argument
+	to 'parse' field.
+	* format-awk.c: Include c-ctype.h, xerror.h, format-invalid.h.
+	(format_parse): Add invalid_reason argument.
+	* format-c.c: Include c-ctype.h, xerror.h, format-invalid.h.
+	(INVALID_C99_MACRO): New macro.
+	(format_parse): Add invalid_reason argument.
+	(get_c99_format_directives): Update.
+	* format-elisp.c: Include c-ctype.h, xerror.h, format-invalid.h.
+	(format_parse): Add invalid_reason argument.
+	* format-java.c: Include xerror.h, format-invalid.h.
+	(message_format_parse, choice_format_parse, format_parse): Add
+	invalid_reason argument.
+	(choice_format_parse): Return false if a choice contains an empty
+	number part.
+	* format-librep.c: Include c-ctype.h, xerror.h, format-invalid.h.
+	(format_parse): Add invalid_reason argument.
+	* format-lisp.c: Include xerror.h, format-invalid.h.
+	(check_params, nocheck_params): Add directives, invalid_reason
+	arguments.
+	(parse_upto, format_parse): Add invalid_reason argument.
+	* format-pascal.c: Include xerror.h, format-invalid.h.
+	(format_parse): Add invalid_reason argument.
+	* format-php.c: Include c-ctype.h, xerror.h, format-invalid.h.
+	(format_parse): Add invalid_reason argument.
+	* format-python.c: Include c-ctype.h, xerror.h, format-invalid.h.
+	(INVALID_MIXES_NAMED_UNNAMED): New macro.
+	(format_parse): Add invalid_reason argument.
+	* format-tcl.c: Include c-ctype.h, xerror.h, format-invalid.h.
+	(format_parse): Add invalid_reason argument.
+	* format-ycp.c: Include c-ctype.h, xerror.h, format-invalid.h.
+	(format_parse): Add invalid_reason argument.
+	* msgfmt.c (check_pair): Output invalid_reason returned for msgstr.
+	* msgmerge.c (msgfmt_check_pair_fails): Update.
+	* xgettext.c (remember_a_message, remember_a_message_plural): Update.
+	* Makefile.am (FORMAT_SOURCE): Add format-invalid.h.
+
 2003-02-22  Bruno Haible  <bruno@clisp.org>
 
 	* x-python.c (init_keywords): Add u*gettext variants and plural
diff --git a/gettext-tools/src/Makefile.am b/gettext-tools/src/Makefile.am
index 6dcce15..14c73c0 100644
--- a/gettext-tools/src/Makefile.am
+++ b/gettext-tools/src/Makefile.am
@@ -87,7 +87,7 @@ po.c po-lex.c po-gram-gen.y po-hash-gen.y po-charset.c \
 open-po.c dir-list.c str-list.c
 
 # xgettext and msgfmt deal with format strings.
-FORMAT_SOURCE = format.c \
+FORMAT_SOURCE = format.c format-invalid.h \
 format-c.c format-python.c format-lisp.c format-elisp.c format-librep.c \
 format-java.c format-awk.c format-pascal.c format-ycp.c format-tcl.c \
 format-php.c
diff --git a/gettext-tools/src/format-awk.c b/gettext-tools/src/format-awk.c
index 0c8bbd5..273cea4 100644
--- a/gettext-tools/src/format-awk.c
+++ b/gettext-tools/src/format-awk.c
@@ -1,5 +1,5 @@
 /* awk format strings.
-   Copyright (C) 2001-2002 Free Software Foundation, Inc.
+   Copyright (C) 2001-2003 Free Software Foundation, Inc.
    Written by Bruno Haible <haible@clisp.cons.org>, 2002.
 
    This program is free software; you can redistribute it and/or modify
@@ -24,7 +24,10 @@
 #include <stdlib.h>
 
 #include "format.h"
+#include "c-ctype.h"
 #include "xmalloc.h"
+#include "xerror.h"
+#include "format-invalid.h"
 #include "error.h"
 #include "progname.h"
 #include "gettext.h"
@@ -93,7 +96,7 @@ numbered_arg_compare (const void *p1, const void *p2)
 }
 
 static void *
-format_parse (const char *format)
+format_parse (const char *format, char **invalid_reason)
 {
   struct spec spec;
   unsigned int unnumbered_arg_count;
@@ -129,7 +132,10 @@ format_parse (const char *format)
 	    if (*f == '$')
 	      {
 		if (m == 0)
-		  goto bad_format;
+		  {
+		    *invalid_reason = INVALID_ARGNO_0 (spec.directives);
+		    goto bad_format;
+		  }
 		number = m;
 		format = ++f;
 	      }
@@ -162,7 +168,11 @@ format_parse (const char *format)
 		if (*f == '$')
 		  {
 		    if (m == 0)
-		      goto bad_format;
+		      {
+			*invalid_reason =
+			  INVALID_WIDTH_ARGNO_0 (spec.directives);
+			goto bad_format;
+		      }
 		    width_number = m;
 		    format = ++f;
 		  }
@@ -174,7 +184,10 @@ format_parse (const char *format)
 
 		/* Numbered and unnumbered specifications are exclusive.  */
 		if (unnumbered_arg_count > 0)
-		  goto bad_format;
+		  {
+		    *invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+		    goto bad_format;
+		  }
 
 		if (spec.allocated == spec.numbered_arg_count)
 		  {
@@ -191,7 +204,10 @@ format_parse (const char *format)
 
 		/* Numbered and unnumbered specifications are exclusive.  */
 		if (spec.numbered_arg_count > 0)
-		  goto bad_format;
+		  {
+		    *invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+		    goto bad_format;
+		  }
 
 		if (spec.allocated == unnumbered_arg_count)
 		  {
@@ -234,7 +250,11 @@ format_parse (const char *format)
 		    if (*f == '$')
 		      {
 			if (m == 0)
-			  goto bad_format;
+			  {
+			    *invalid_reason =
+			      INVALID_PRECISION_ARGNO_0 (spec.directives);
+			    goto bad_format;
+			  }
 			precision_number = m;
 			format = ++f;
 		      }
@@ -246,7 +266,10 @@ format_parse (const char *format)
 
 		    /* Numbered and unnumbered specifications are exclusive.  */
 		    if (unnumbered_arg_count > 0)
-		      goto bad_format;
+		      {
+			*invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+			goto bad_format;
+		      }
 
 		    if (spec.allocated == spec.numbered_arg_count)
 		      {
@@ -263,7 +286,10 @@ format_parse (const char *format)
 
 		    /* Numbered and unnumbered specifications are exclusive.  */
 		    if (spec.numbered_arg_count > 0)
-		      goto bad_format;
+		      {
+			*invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+			goto bad_format;
+		      }
 
 		    if (spec.allocated == unnumbered_arg_count)
 		      {
@@ -302,6 +328,10 @@ format_parse (const char *format)
 	    type = FAT_FLOAT;
 	    break;
 	  default:
+	    *invalid_reason =
+	      (*format == '\0'
+	       ? INVALID_UNTERMINATED_DIRECTIVE ()
+	       : INVALID_CONVERSION_SPECIFIER (spec.directives, *format));
 	    goto bad_format;
 	  }
 
@@ -313,7 +343,10 @@ format_parse (const char *format)
 
 		/* Numbered and unnumbered specifications are exclusive.  */
 		if (unnumbered_arg_count > 0)
-		  goto bad_format;
+		  {
+		    *invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+		    goto bad_format;
+		  }
 
 		if (spec.allocated == spec.numbered_arg_count)
 		  {
@@ -330,7 +363,10 @@ format_parse (const char *format)
 
 		/* Numbered and unnumbered specifications are exclusive.  */
 		if (spec.numbered_arg_count > 0)
-		  goto bad_format;
+		  {
+		    *invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+		    goto bad_format;
+		  }
 
 		if (spec.allocated == unnumbered_arg_count)
 		  {
@@ -370,8 +406,14 @@ format_parse (const char *format)
 	    if (type1 == type2)
 	      type_both = type1;
 	    else
-	      /* Incompatible types.  */
-	      type_both = FAT_NONE, err = true;
+	      {
+		/* Incompatible types.  */
+		type_both = FAT_NONE;
+		if (!err)
+		  *invalid_reason =
+		    INVALID_INCOMPATIBLE_ARG_TYPES (spec.numbered[i].number);
+		err = true;
+	      }
 
 	    spec.numbered[j-1].type = type_both;
 	  }
@@ -386,6 +428,7 @@ format_parse (const char *format)
 	  }
       spec.numbered_arg_count = j;
       if (err)
+	/* *invalid_reason has already been set above.  */
 	goto bad_format;
     }
 
@@ -579,17 +622,26 @@ main ()
   for (;;)
     {
       char *line = NULL;
-      size_t line_len = 0;
+      size_t line_size = 0;
+      int line_len;
+      char *invalid_reason;
       void *descr;
 
-      if (getline (&line, &line_len, stdin) < 0)
+      line_len = getline (&line, &line_size, stdin);
+      if (line_len < 0)
 	break;
+      if (line_len > 0 && line[line_len - 1] == '\n')
+	line[--line_len] = '\0';
 
-      descr = format_parse (line);
+      invalid_reason = NULL;
+      descr = format_parse (line, &invalid_reason);
 
       format_print (descr);
       printf ("\n");
+      if (descr == NULL)
+	printf ("%s\n", invalid_reason);
 
+      free (invalid_reason);
       free (line);
     }
 
diff --git a/gettext-tools/src/format-c.c b/gettext-tools/src/format-c.c
index 81300ca..4eb3c2c 100644
--- a/gettext-tools/src/format-c.c
+++ b/gettext-tools/src/format-c.c
@@ -24,7 +24,10 @@
 #include <stdlib.h>
 
 #include "format.h"
+#include "c-ctype.h"
 #include "xmalloc.h"
+#include "xerror.h"
+#include "format-invalid.h"
 #include "error.h"
 #include "progname.h"
 #include "gettext.h"
@@ -169,8 +172,11 @@ numbered_arg_compare (const void *p1, const void *p2)
   return (n1 > n2 ? 1 : n1 < n2 ? -1 : 0);
 }
 
+#define INVALID_C99_MACRO(directive_number) \
+  xasprintf (_("In the directive number %u, the token after '<' is not the name of a format specifier macro. The valid macro names are listed in ISO C 99 section 7.8.1."), directive_number)
+
 static void *
-format_parse (const char *format)
+format_parse (const char *format, char **invalid_reason)
 {
   struct spec spec;
   unsigned int numbered_arg_count;
@@ -211,7 +217,10 @@ format_parse (const char *format)
 	    if (*f == '$')
 	      {
 		if (m == 0)
-		  goto bad_format;
+		  {
+		    *invalid_reason = INVALID_ARGNO_0 (spec.directives);
+		    goto bad_format;
+		  }
 		number = m;
 		format = ++f;
 	      }
@@ -244,7 +253,11 @@ format_parse (const char *format)
 		if (*f == '$')
 		  {
 		    if (m == 0)
-		      goto bad_format;
+		      {
+			*invalid_reason =
+			  INVALID_WIDTH_ARGNO_0 (spec.directives);
+			goto bad_format;
+		      }
 		    width_number = m;
 		    format = ++f;
 		  }
@@ -256,7 +269,10 @@ format_parse (const char *format)
 
 		/* Numbered and unnumbered specifications are exclusive.  */
 		if (spec.unnumbered_arg_count > 0)
-		  goto bad_format;
+		  {
+		    *invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+		    goto bad_format;
+		  }
 
 		if (spec.allocated == numbered_arg_count)
 		  {
@@ -273,7 +289,10 @@ format_parse (const char *format)
 
 		/* Numbered and unnumbered specifications are exclusive.  */
 		if (numbered_arg_count > 0)
-		  goto bad_format;
+		  {
+		    *invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+		    goto bad_format;
+		  }
 
 		if (spec.allocated == spec.unnumbered_arg_count)
 		  {
@@ -315,7 +334,11 @@ format_parse (const char *format)
 		    if (*f == '$')
 		      {
 			if (m == 0)
-			  goto bad_format;
+			  {
+			    *invalid_reason =
+			      INVALID_PRECISION_ARGNO_0 (spec.directives);
+			    goto bad_format;
+			  }
 			precision_number = m;
 			format = ++f;
 		      }
@@ -327,7 +350,10 @@ format_parse (const char *format)
 
 		    /* Numbered and unnumbered specifications are exclusive.  */
 		    if (spec.unnumbered_arg_count > 0)
-		      goto bad_format;
+		      {
+			*invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+			goto bad_format;
+		      }
 
 		    if (spec.allocated == numbered_arg_count)
 		      {
@@ -344,7 +370,10 @@ format_parse (const char *format)
 
 		    /* Numbered and unnumbered specifications are exclusive.  */
 		    if (numbered_arg_count > 0)
-		      goto bad_format;
+		      {
+			*invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+			goto bad_format;
+		      }
 
 		    if (spec.allocated == spec.unnumbered_arg_count)
 		      {
@@ -376,13 +405,22 @@ format_parse (const char *format)
 	       P R I { d | i | o | u | x | X }
 	       { { | LEAST | FAST } { 8 | 16 | 32 | 64 } | MAX | PTR }  */
 	    if (*format != 'P')
-	      goto bad_format;
+	      {
+		*invalid_reason = INVALID_C99_MACRO (spec.directives);
+		goto bad_format;
+	      }
 	    format++;
 	    if (*format != 'R')
-	      goto bad_format;
+	      {
+		*invalid_reason = INVALID_C99_MACRO (spec.directives);
+		goto bad_format;
+	      }
 	    format++;
 	    if (*format != 'I')
-	      goto bad_format;
+	      {
+		*invalid_reason = INVALID_C99_MACRO (spec.directives);
+		goto bad_format;
+	      }
 	    format++;
 
 	    switch (*format)
@@ -394,6 +432,7 @@ format_parse (const char *format)
 		type = FAT_INTEGER | FAT_UNSIGNED;
 		break;
 	      default:
+		*invalid_reason = INVALID_C99_MACRO (spec.directives);
 		goto bad_format;
 	      }
 	    format++;
@@ -435,7 +474,10 @@ format_parse (const char *format)
 			format += 2;
 		      }
 		    else
-		      goto bad_format;
+		      {
+			*invalid_reason = INVALID_C99_MACRO (spec.directives);
+			goto bad_format;
+		      }
 		  }
 		else if (format[0] == 'F' && format[1] == 'A'
 			 && format[2] == 'S' && format[3] == 'T')
@@ -462,7 +504,10 @@ format_parse (const char *format)
 			format += 2;
 		      }
 		    else
-		      goto bad_format;
+		      {
+			*invalid_reason = INVALID_C99_MACRO (spec.directives);
+			goto bad_format;
+		      }
 		  }
 		else
 		  {
@@ -487,12 +532,19 @@ format_parse (const char *format)
 			format += 2;
 		      }
 		    else
-		      goto bad_format;
+		      {
+			*invalid_reason = INVALID_C99_MACRO (spec.directives);
+			goto bad_format;
+		      }
 		  }
 	      }
 
 	    if (*format != '>')
-	      goto bad_format;
+	      {
+		*invalid_reason =
+		  xasprintf (_("In the directive number %u, the token after '<' is not followed by '>'."), spec.directives);
+		goto bad_format;
+	      }
 
 	    spec.c99_directives[2 * spec.c99_directives_count + 1] = format;
 	    spec.c99_directives_count++;
@@ -578,6 +630,10 @@ format_parse (const char *format)
 		type |= (size & FAT_SIZE_MASK);
 		break;
 	      default:
+		*invalid_reason =
+		  (*format == '\0'
+		   ? INVALID_UNTERMINATED_DIRECTIVE ()
+		   : INVALID_CONVERSION_SPECIFIER (spec.directives, *format));
 		goto bad_format;
 	      }
 	  }
@@ -590,7 +646,10 @@ format_parse (const char *format)
 
 		/* Numbered and unnumbered specifications are exclusive.  */
 		if (spec.unnumbered_arg_count > 0)
-		  goto bad_format;
+		  {
+		    *invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+		    goto bad_format;
+		  }
 
 		if (spec.allocated == numbered_arg_count)
 		  {
@@ -607,7 +666,10 @@ format_parse (const char *format)
 
 		/* Numbered and unnumbered specifications are exclusive.  */
 		if (numbered_arg_count > 0)
-		  goto bad_format;
+		  {
+		    *invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+		    goto bad_format;
+		  }
 
 		if (spec.allocated == spec.unnumbered_arg_count)
 		  {
@@ -643,8 +705,14 @@ format_parse (const char *format)
 	    if (type1 == type2)
 	      type_both = type1;
 	    else
-	      /* Incompatible types.  */
-	      type_both = FAT_NONE, err = true;
+	      {
+		/* Incompatible types.  */
+		type_both = FAT_NONE;
+		if (!err)
+		  *invalid_reason =
+		    INVALID_INCOMPATIBLE_ARG_TYPES (numbered[i].number);
+		err = true;
+	      }
 
 	    numbered[j-1].type = type_both;
 	  }
@@ -659,6 +727,7 @@ format_parse (const char *format)
 	  }
       numbered_arg_count = j;
       if (err)
+	/* *invalid_reason has already been set above.  */
 	goto bad_format;
     }
 
@@ -670,7 +739,11 @@ format_parse (const char *format)
 
       for (i = 0; i < numbered_arg_count; i++)
 	if (numbered[i].number != i + 1)
-	  goto bad_format;
+	  {
+	    *invalid_reason =
+	      xasprintf (_("The string refers to argument number %u but ignores argument number %u."), numbered[i].number, i + 1);
+	    goto bad_format;
+	  }
 
       /* So now the numbered arguments array is equivalent to a sequence
 	 of unnumbered arguments.  */
@@ -773,7 +846,8 @@ void
 get_c99_format_directives (const char *string,
 			   struct interval **intervalsp, size_t *lengthp)
 {
-  struct spec *descr = (struct spec *) format_parse (string);
+  char *invalid_reason = NULL;
+  struct spec *descr = (struct spec *) format_parse (string, &invalid_reason);
 
   if (descr != NULL && descr->c99_directives_count > 0)
     {
@@ -798,6 +872,8 @@ get_c99_format_directives (const char *string,
 
   if (descr != NULL)
     format_free (descr);
+  else
+    free (invalid_reason);
 }
 
 
@@ -928,17 +1004,26 @@ main ()
   for (;;)
     {
       char *line = NULL;
-      size_t line_len = 0;
+      size_t line_size = 0;
+      int line_len;
+      char *invalid_reason;
       void *descr;
 
-      if (getline (&line, &line_len, stdin) < 0)
+      line_len = getline (&line, &line_size, stdin);
+      if (line_len < 0)
 	break;
+      if (line_len > 0 && line[line_len - 1] == '\n')
+	line[--line_len] = '\0';
 
-      descr = format_parse (line);
+      invalid_reason = NULL;
+      descr = format_parse (line, &invalid_reason);
 
       format_print (descr);
       printf ("\n");
+      if (descr == NULL)
+	printf ("%s\n", invalid_reason);
 
+      free (invalid_reason);
       free (line);
     }
 
diff --git a/gettext-tools/src/format-elisp.c b/gettext-tools/src/format-elisp.c
index b121a4c..f575e3a 100644
--- a/gettext-tools/src/format-elisp.c
+++ b/gettext-tools/src/format-elisp.c
@@ -1,5 +1,5 @@
 /* Emacs Lisp format strings.
-   Copyright (C) 2001-2002 Free Software Foundation, Inc.
+   Copyright (C) 2001-2003 Free Software Foundation, Inc.
    Written by Bruno Haible <haible@clisp.cons.org>, 2002.
 
    This program is free software; you can redistribute it and/or modify
@@ -24,7 +24,10 @@
 #include <stdlib.h>
 
 #include "format.h"
+#include "c-ctype.h"
 #include "xmalloc.h"
+#include "xerror.h"
+#include "format-invalid.h"
 #include "error.h"
 #include "progname.h"
 #include "gettext.h"
@@ -94,7 +97,7 @@ numbered_arg_compare (const void *p1, const void *p2)
 }
 
 static void *
-format_parse (const char *format)
+format_parse (const char *format, char **invalid_reason)
 {
   struct spec spec;
   struct spec *result;
@@ -206,6 +209,10 @@ format_parse (const char *format)
 	    type = FAT_OBJECT;
 	    break;
 	  default:
+	    *invalid_reason =
+	      (*format == '\0'
+	       ? INVALID_UNTERMINATED_DIRECTIVE ()
+	       : INVALID_CONVERSION_SPECIFIER (spec.directives, *format));
 	    goto bad_format;
 	  }
 
@@ -247,8 +254,14 @@ format_parse (const char *format)
 	    if (type1 == type2)
 	      type_both = type1;
 	    else
-	      /* Incompatible types.  */
-	      type_both = FAT_NONE, err = true;
+	      {
+		/* Incompatible types.  */
+		type_both = FAT_NONE;
+		if (!err)
+		  *invalid_reason =
+		    INVALID_INCOMPATIBLE_ARG_TYPES (spec.numbered[i].number);
+		err = true;
+	      }
 
 	    spec.numbered[j-1].type = type_both;
 	  }
@@ -263,6 +276,7 @@ format_parse (const char *format)
 	  }
       spec.numbered_arg_count = j;
       if (err)
+	/* *invalid_reason has already been set above.  */
 	goto bad_format;
     }
 
@@ -456,17 +470,26 @@ main ()
   for (;;)
     {
       char *line = NULL;
-      size_t line_len = 0;
+      size_t line_size = 0;
+      int line_len;
+      char *invalid_reason;
       void *descr;
 
-      if (getline (&line, &line_len, stdin) < 0)
+      line_len = getline (&line, &line_size, stdin);
+      if (line_len < 0)
 	break;
+      if (line_len > 0 && line[line_len - 1] == '\n')
+	line[--line_len] = '\0';
 
-      descr = format_parse (line);
+      invalid_reason = NULL;
+      descr = format_parse (line, &invalid_reason);
 
       format_print (descr);
       printf ("\n");
+      if (descr == NULL)
+	printf ("%s\n", invalid_reason);
 
+      free (invalid_reason);
       free (line);
     }
 
diff --git a/gettext-tools/src/format-invalid.h b/gettext-tools/src/format-invalid.h
new file mode 100644
index 0000000..8e98a62
--- /dev/null
+++ b/gettext-tools/src/format-invalid.h
@@ -0,0 +1,41 @@
+/* Common reasons that make a format string invalid.
+   Copyright (C) 2003 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2003.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+/* These macros return freshly allocated error message strings, intended
+   to be stored in *invalid_reason.  */
+
+#define INVALID_UNTERMINATED_DIRECTIVE() \
+  xstrdup (_("The string ends in the middle of a directive."))
+
+#define INVALID_MIXES_NUMBERED_UNNUMBERED() \
+  xstrdup (_("The string refers to arguments both through absolute argument numbers and through unnumbered argument specifications."))
+
+#define INVALID_ARGNO_0(directive_number) \
+  xasprintf (_("In the directive number %u, the argument number 0 is not a positive integer."), directive_number)
+#define INVALID_WIDTH_ARGNO_0(directive_number) \
+  xasprintf (_("In the directive number %u, the width's argument number 0 is not a positive integer."), directive_number)
+#define INVALID_PRECISION_ARGNO_0(directive_number) \
+  xasprintf (_("In the directive number %u, the precision's argument number 0 is not a positive integer."), directive_number)
+
+#define INVALID_CONVERSION_SPECIFIER(directive_number,conv_char) \
+  (c_isprint (conv_char) \
+   ? xasprintf (_("In the directive number %u, the character '%c' is not a valid conversion specifier."), directive_number, conv_char) \
+   : xasprintf (_("The character that terminates the directive number %u is not a valid conversion specifier."), directive_number))
+
+#define INVALID_INCOMPATIBLE_ARG_TYPES(arg_number) \
+  xasprintf (_("The string refers to argument number %u in incompatible ways."), arg_number)
diff --git a/gettext-tools/src/format-java.c b/gettext-tools/src/format-java.c
index f448804..e8ba904 100644
--- a/gettext-tools/src/format-java.c
+++ b/gettext-tools/src/format-java.c
@@ -28,6 +28,8 @@
 #include "format.h"
 #include "c-ctype.h"
 #include "xmalloc.h"
+#include "xerror.h"
+#include "format-invalid.h"
 #include "error.h"
 #include "progname.h"
 #include "gettext.h"
@@ -129,7 +131,8 @@ struct spec
 /* Forward declaration of local functions.  */
 static bool date_format_parse (const char *format);
 static bool number_format_parse (const char *format);
-static bool choice_format_parse (const char *format, struct spec *spec);
+static bool choice_format_parse (const char *format, struct spec *spec,
+				 char **invalid_reason);
 
 
 /* Quote handling:
@@ -147,7 +150,8 @@ static bool choice_format_parse (const char *format, struct spec *spec);
 /* Return true if a format is a valid messageFormatPattern.
    Extracts argument type information into spec.  */
 static bool
-message_format_parse (const char *format, struct spec *spec)
+message_format_parse (const char *format, struct spec *spec,
+		      char **invalid_reason)
 {
   bool quoting = false;
 
@@ -181,7 +185,11 @@ message_format_parse (const char *format, struct spec *spec)
 		}
 	    }
 	  if (*format == '\0')
-	    return false;
+	    {
+	      *invalid_reason =
+		xstrdup (_("The string ends in the middle of a directive: found '{' without matching '}'."));
+	      return false;
+	    }
 	  element_end = format++;
 
 	  n = element_end - element_start;
@@ -190,7 +198,11 @@ message_format_parse (const char *format, struct spec *spec)
 	  element[n] = '\0';
 
 	  if (!c_isdigit (*element))
-	    return false;
+	    {
+	      *invalid_reason =
+		xasprintf (_("In the directive number %u, '{' is not followed by an argument number."), spec->directives);
+	      return false;
+	    }
 	  number = 0;
 	  do
 	    {
@@ -209,15 +221,30 @@ message_format_parse (const char *format, struct spec *spec)
 	      element += 5;
 	      if (*element == '\0')
 		;
-	      else if (*element++ == ','
-		       && (strcmp (element, "short") == 0
-			   || strcmp (element, "medium") == 0
-			   || strcmp (element, "long") == 0
-			   || strcmp (element, "full") == 0
-			   || date_format_parse (element)))
-		;
+	      else if (*element == ',')
+		{
+		  element++;
+		  if (strcmp (element, "short") == 0
+		      || strcmp (element, "medium") == 0
+		      || strcmp (element, "long") == 0
+		      || strcmp (element, "full") == 0
+		      || date_format_parse (element))
+		    ;
+		  else
+		    {
+		      *invalid_reason =
+			xasprintf (_("In the directive number %u, the substring \"%s\" is not a valid date/time style."), spec->directives, element);
+		      return false;
+		    }
+		}
 	      else
-		return false;
+		{
+		  *element = '\0';
+		  element -= 4;
+		  *invalid_reason =
+		    xasprintf (_("In the directive number %u, \"%s\" is not followed by a comma."), spec->directives, element);
+		  return false;
+		}
 	    }
 	  else if (strncmp (element, ",number", 7) == 0)
 	    {
@@ -225,14 +252,29 @@ message_format_parse (const char *format, struct spec *spec)
 	      element += 7;
 	      if (*element == '\0')
 		;
-	      else if (*element++ == ','
-		       && (strcmp (element, "currency") == 0
-			   || strcmp (element, "percent") == 0
-			   || strcmp (element, "integer") == 0
-			   || number_format_parse (element)))
-		;
+	      else if (*element == ',')
+		{
+		  element++;
+		  if (strcmp (element, "currency") == 0
+		      || strcmp (element, "percent") == 0
+		      || strcmp (element, "integer") == 0
+		      || number_format_parse (element))
+		    ;
+		  else
+		    {
+		      *invalid_reason =
+			xasprintf (_("In the directive number %u, the substring \"%s\" is not a valid number style."), spec->directives, element);
+		      return false;
+		    }
+		}
 	      else
-		return false;
+		{
+		  *element = '\0';
+		  element -= 6;
+		  *invalid_reason =
+		    xasprintf (_("In the directive number %u, \"%s\" is not followed by a comma."), spec->directives, element);
+		  return false;
+		}
 	    }
 	  else if (strncmp (element, ",choice", 7) == 0)
 	    {
@@ -240,14 +282,29 @@ message_format_parse (const char *format, struct spec *spec)
 	      element += 7;
 	      if (*element == '\0')
 		;
-	      else if (*element++ == ','
-		       && choice_format_parse (element, spec))
-		;
+	      else if (*element == ',')
+		{
+		  element++;
+		  if (choice_format_parse (element, spec, invalid_reason))
+		    ;
+		  else
+		    return false;
+		}
 	      else
-		return false;
+		{
+		  *element = '\0';
+		  element -= 6;
+		  *invalid_reason =
+		    xasprintf (_("In the directive number %u, \"%s\" is not followed by a comma."), spec->directives, element);
+		  return false;
+		}
 	    }
 	  else
-	    return false;
+	    {
+	      *invalid_reason =
+		xasprintf (_("In the directive number %u, the argument number is not followed by a comma and one of \"%s\", \"%s\", \"%s\", \"%s\"."), spec->directives, "time", "date", "number", "choice");
+	      return false;
+	    }
 
 	  if (spec->allocated == spec->numbered_arg_count)
 	    {
@@ -260,7 +317,11 @@ message_format_parse (const char *format, struct spec *spec)
 	}
       /* The doc says "ab}de" is invalid.  Even though JDK accepts it.  */
       else if (!quoting && *format == '}')
-	return false;
+	{
+	  *invalid_reason =
+	    xstrdup (_("The string starts in the middle of a directive: found '}' without matching '{'."));
+	  return false;
+	}
       else if (*format != '\0')
 	format++;
       else
@@ -427,7 +488,8 @@ number_format_parse (const char *format)
 /* Return true if a format is a valid choiceFormatPattern.
    Extracts argument type information into spec.  */
 static bool
-choice_format_parse (const char *format, struct spec *spec)
+choice_format_parse (const char *format, struct spec *spec,
+		     char **invalid_reason)
 {
   /* Pattern syntax:
        pattern   := | choice | choice '|' pattern
@@ -446,10 +508,12 @@ choice_format_parse (const char *format, struct spec *spec)
     {
       /* Don't bother looking too precisely into the syntax of the number.
 	 It can contain various Unicode characters.  */
+      bool number_nonempty;
       char *msgformat;
       char *mp;
 
       /* Parse number.  */
+      number_nonempty = false;
       while (*format != '\0'
 	     && !(!quoting && (*format == '<' || *format == '#'
 			       || strncmp (format, "\\u2264", 6) == 0
@@ -468,6 +532,7 @@ choice_format_parse (const char *format, struct spec *spec)
 	    }
 	  else
 	    format += 1;
+	  number_nonempty = true;
 	  HANDLE_QUOTE;
 	}
 
@@ -475,12 +540,23 @@ choice_format_parse (const char *format, struct spec *spec)
       if (*format == '\0')
 	break;
 
+      if (!number_nonempty)
+	{
+	  *invalid_reason =
+	    xasprintf (_("In the directive number %u, a choice contains no number."), spec->directives);
+	  return false;
+	}
+
       if (*format == '<' || *format == '#')
 	format += 1;
       else if (strncmp (format, "\\u2264", 6) == 0)
 	format += 6;
       else
-	return false;
+	{
+	  *invalid_reason =
+	    xasprintf (_("In the directive number %u, a choice contains a number that is not followed by '<', '#' or '%s'."), spec->directives, "\\u2264");
+	  return false;
+	}
       HANDLE_QUOTE;
 
       msgformat = (char *) alloca (strlen (format) + 1);
@@ -493,7 +569,7 @@ choice_format_parse (const char *format, struct spec *spec)
 	}
       *mp = '\0';
 
-      if (!message_format_parse (msgformat, spec))
+      if (!message_format_parse (msgformat, spec, invalid_reason))
 	return false;
 
       if (*format == '\0')
@@ -516,7 +592,7 @@ numbered_arg_compare (const void *p1, const void *p2)
 }
 
 static void *
-format_parse (const char *format)
+format_parse (const char *format, char **invalid_reason)
 {
   struct spec spec;
   struct spec *result;
@@ -526,7 +602,7 @@ format_parse (const char *format)
   spec.allocated = 0;
   spec.numbered = NULL;
 
-  if (!message_format_parse (format, &spec))
+  if (!message_format_parse (format, &spec, invalid_reason))
     goto bad_format;
 
   /* Sort the numbered argument array, and eliminate duplicates.  */
@@ -552,8 +628,14 @@ format_parse (const char *format)
 	    else if (type1 == FAT_OBJECT)
 	      type_both = type2;
 	    else
-	      /* Incompatible types.  */
-	      type_both = FAT_NONE, err = true;
+	      {
+		/* Incompatible types.  */
+		type_both = FAT_NONE;
+		if (!err)
+		  *invalid_reason =
+		    INVALID_INCOMPATIBLE_ARG_TYPES (spec.numbered[i].number);
+		err = true;
+	      }
 
 	    spec.numbered[j-1].type = type_both;
 	  }
@@ -568,6 +650,7 @@ format_parse (const char *format)
 	  }
       spec.numbered_arg_count = j;
       if (err)
+	/* *invalid_reason has already been set above.  */
 	goto bad_format;
     }
 
@@ -755,17 +838,26 @@ main ()
   for (;;)
     {
       char *line = NULL;
-      size_t line_len = 0;
+      size_t line_size = 0;
+      int line_len;
+      char *invalid_reason;
       void *descr;
 
-      if (getline (&line, &line_len, stdin) < 0)
+      line_len = getline (&line, &line_size, stdin);
+      if (line_len < 0)
 	break;
+      if (line_len > 0 && line[line_len - 1] == '\n')
+	line[--line_len] = '\0';
 
-      descr = format_parse (line);
+      invalid_reason = NULL;
+      descr = format_parse (line, &invalid_reason);
 
       format_print (descr);
       printf ("\n");
+      if (descr == NULL)
+	printf ("%s\n", invalid_reason);
 
+      free (invalid_reason);
       free (line);
     }
 
diff --git a/gettext-tools/src/format-librep.c b/gettext-tools/src/format-librep.c
index 71cad3f..2dfcaa4 100644
--- a/gettext-tools/src/format-librep.c
+++ b/gettext-tools/src/format-librep.c
@@ -1,5 +1,5 @@
 /* librep format strings.
-   Copyright (C) 2001-2002 Free Software Foundation, Inc.
+   Copyright (C) 2001-2003 Free Software Foundation, Inc.
    Written by Bruno Haible <haible@clisp.cons.org>, 2001.
 
    This program is free software; you can redistribute it and/or modify
@@ -24,7 +24,10 @@
 #include <stdlib.h>
 
 #include "format.h"
+#include "c-ctype.h"
 #include "xmalloc.h"
+#include "xerror.h"
+#include "format-invalid.h"
 #include "error.h"
 #include "progname.h"
 #include "gettext.h"
@@ -91,7 +94,7 @@ numbered_arg_compare (const void *p1, const void *p2)
 }
 
 static void *
-format_parse (const char *format)
+format_parse (const char *format, char **invalid_reason)
 {
   struct spec spec;
   struct spec *result;
@@ -170,6 +173,10 @@ format_parse (const char *format)
 	    type = FAT_OBJECT;
 	    break;
 	  default:
+	    *invalid_reason =
+	      (*format == '\0'
+	       ? INVALID_UNTERMINATED_DIRECTIVE ()
+	       : INVALID_CONVERSION_SPECIFIER (spec.directives, *format));
 	    goto bad_format;
 	  }
 
@@ -211,8 +218,14 @@ format_parse (const char *format)
 	    if (type1 == type2)
 	      type_both = type1;
 	    else
-	      /* Incompatible types.  */
-	      type_both = FAT_NONE, err = true;
+	      {
+		/* Incompatible types.  */
+		type_both = FAT_NONE;
+		if (!err)
+		  *invalid_reason =
+		    INVALID_INCOMPATIBLE_ARG_TYPES (spec.numbered[i].number);
+		err = true;
+	      }
 
 	    spec.numbered[j-1].type = type_both;
 	  }
@@ -227,6 +240,7 @@ format_parse (const char *format)
 	  }
       spec.numbered_arg_count = j;
       if (err)
+	/* *invalid_reason has already been set above.  */
 	goto bad_format;
     }
 
@@ -417,17 +431,26 @@ main ()
   for (;;)
     {
       char *line = NULL;
-      size_t line_len = 0;
+      size_t line_size = 0;
+      int line_len;
+      char *invalid_reason;
       void *descr;
 
-      if (getline (&line, &line_len, stdin) < 0)
+      line_len = getline (&line, &line_size, stdin);
+      if (line_len < 0)
 	break;
+      if (line_len > 0 && line[line_len - 1] == '\n')
+	line[--line_len] = '\0';
 
-      descr = format_parse (line);
+      invalid_reason = NULL;
+      descr = format_parse (line, &invalid_reason);
 
       format_print (descr);
       printf ("\n");
+      if (descr == NULL)
+	printf ("%s\n", invalid_reason);
 
+      free (invalid_reason);
       free (line);
     }
 
diff --git a/gettext-tools/src/format-lisp.c b/gettext-tools/src/format-lisp.c
index 745c95d..51cf6ee 100644
--- a/gettext-tools/src/format-lisp.c
+++ b/gettext-tools/src/format-lisp.c
@@ -1,5 +1,5 @@
 /* Lisp format strings.
-   Copyright (C) 2001-2002 Free Software Foundation, Inc.
+   Copyright (C) 2001-2003 Free Software Foundation, Inc.
    Written by Bruno Haible <haible@clisp.cons.org>, 2001.
 
    This program is free software; you can redistribute it and/or modify
@@ -27,6 +27,8 @@
 #include "c-ctype.h"
 #include "gcd.h"
 #include "xmalloc.h"
+#include "xerror.h"
+#include "format-invalid.h"
 #include "minmax.h"
 #include "error.h"
 #include "progname.h"
@@ -2323,12 +2325,17 @@ static const enum format_arg_type THREE [3] = {
 
 
 /* Check the parameters.  For V params, add the constraint to the argument
-   list.  Return false if the format string is invalid.  */
+   list.  Return false and fill in *invalid_reason if the format string is
+   invalid.  */
 static bool
 check_params (struct format_arg_list **listp,
 	      unsigned int paramcount, struct param *params,
-	      unsigned int t_count, const enum format_arg_type *t_types)
+	      unsigned int t_count, const enum format_arg_type *t_types,
+	      unsigned int directives, char **invalid_reason)
 {
+  unsigned int orig_paramcount = paramcount;
+  unsigned int orig_t_count = t_count;
+
   for (; paramcount > 0 && t_count > 0;
 	 params++, paramcount--, t_types++, t_count--)
     {
@@ -2342,7 +2349,10 @@ check_params (struct format_arg_list **listp,
 	    case PT_NIL: case PT_CHARACTER: case PT_V:
 	      break;
 	    case PT_INTEGER: case PT_ARGCOUNT:
-	      return false; /* wrong param type */
+	      /* wrong param type */
+	      *invalid_reason =
+		xasprintf (_("In the directive number %u, parameter %u is of type '%s' but a parameter of type '%s' is expected."), directives, orig_paramcount - paramcount + 1, "integer", "character");
+	      return false;
 	    }
 	  break;
 	case FAT_INTEGER_NULL:
@@ -2351,7 +2361,10 @@ check_params (struct format_arg_list **listp,
 	    case PT_NIL: case PT_INTEGER: case PT_ARGCOUNT: case PT_V:
 	      break;
 	    case PT_CHARACTER:
-	      return false; /* wrong param type */
+	      /* wrong param type */
+	      *invalid_reason =
+		xasprintf (_("In the directive number %u, parameter %u is of type '%s' but a parameter of type '%s' is expected."), directives, orig_paramcount - paramcount + 1, "character", "integer");
+	      return false;
 	    }
 	  break;
 	default:
@@ -2371,7 +2384,10 @@ check_params (struct format_arg_list **listp,
       case PT_NIL:
 	break;
       case PT_CHARACTER: case PT_INTEGER: case PT_ARGCOUNT:
-	return false; /* too many params for directive */
+	/* too many params for directive */
+	*invalid_reason =
+	  xasprintf (_("In the directive number %u, too many parameters are given; expected at most %u parameters."), directives, orig_t_count);
+	return false;
       case PT_V:
 	/* Force argument to be NIL.  */
 	{
@@ -2393,11 +2409,16 @@ check_params (struct format_arg_list **listp,
 
 /* Handle the parameters, without a priori type information.
    For V params, add the constraint to the argument list.
-   Return false if the format string is invalid.  */
+   Return false and fill in *invalid_reason if the format string is
+   invalid.  */
 static bool
 nocheck_params (struct format_arg_list **listp,
-		unsigned int paramcount, struct param *params)
+		unsigned int paramcount, struct param *params,
+		unsigned int directives, char **invalid_reason)
 {
+  (void) directives;
+  (void) invalid_reason;
+
   for (; paramcount > 0; params++, paramcount--)
     if (params->type == PT_V)
       {
@@ -2426,12 +2447,14 @@ nocheck_params (struct format_arg_list **listp,
    spec is the global struct spec.
    terminator is the directive that terminates this parse.
    separator specifies if ~; separators are allowed.
-   If the format string is invalid, false is returned.  */
+   If the format string is invalid, false is returned and *invalid_reason is
+   set to an error message explaining why.  */
 static bool
 parse_upto (const char **formatp,
 	    int *positionp, struct format_arg_list **listp,
 	    struct format_arg_list **escapep, int *separatorp,
-	    struct spec *spec, char terminator, bool separator)
+	    struct spec *spec, char terminator, bool separator,
+	    char **invalid_reason)
 {
   const char *format = *formatp;
   int position = *positionp;
@@ -2471,7 +2494,13 @@ parse_upto (const char **formatp,
 		type = PT_INTEGER;
 		format++;
 		if (!c_isdigit (*format))
-		  return false;
+		  {
+		    *invalid_reason =
+		      (*format == '\0'
+		       ? INVALID_UNTERMINATED_DIRECTIVE ()
+		       : xasprintf (_("In the directive number %u, '%c' is not followed by a digit."), spec->directives, format[-1]));
+		    return false;
+		  }
 		do
 		  {
 		    value = 10 * value + (*format - '0');
@@ -2486,7 +2515,10 @@ parse_upto (const char **formatp,
 		type = PT_CHARACTER;
 		format++;
 		if (*format == '\0')
-		  return false;
+		  {
+		    *invalid_reason = INVALID_UNTERMINATED_DIRECTIVE ();
+		    return false;
+		  }
 		format++;
 	      }
 	    else if (*format == 'V' || *format == 'v')
@@ -2539,14 +2571,16 @@ parse_upto (const char **formatp,
 	  {
 	  case 'A': case 'a': /* 22.3.4.1 FORMAT-ASCII */
 	  case 'S': case 's': /* 22.3.4.2 FORMAT-S-EXPRESSION */
-	    if (!check_params (&list, paramcount, params, 4, IIIC))
+	    if (!check_params (&list, paramcount, params, 4, IIIC,
+			       spec->directives, invalid_reason))
 	      return false;
 	    if (position >= 0)
 	      add_req_type_constraint (&list, position++, FAT_OBJECT);
 	    break;
 
 	  case 'W': case 'w': /* 22.3.4.3 FORMAT-WRITE */
-	    if (!check_params (&list, paramcount, params, 0, NULL))
+	    if (!check_params (&list, paramcount, params, 0, NULL,
+			       spec->directives, invalid_reason))
 	      return false;
 	    if (position >= 0)
 	      add_req_type_constraint (&list, position++, FAT_OBJECT);
@@ -2556,21 +2590,24 @@ parse_upto (const char **formatp,
 	  case 'B': case 'b': /* 22.3.2.3 FORMAT-BINARY */
 	  case 'O': case 'o': /* 22.3.2.4 FORMAT-OCTAL */
 	  case 'X': case 'x': /* 22.3.2.5 FORMAT-HEXADECIMAL */
-	    if (!check_params (&list, paramcount, params, 4, ICCI))
+	    if (!check_params (&list, paramcount, params, 4, ICCI,
+			       spec->directives, invalid_reason))
 	      return false;
 	    if (position >= 0)
 	      add_req_type_constraint (&list, position++, FAT_INTEGER);
 	    break;
 
 	  case 'R': case 'r': /* 22.3.2.1 FORMAT-RADIX */
-	    if (!check_params (&list, paramcount, params, 5, IICCI))
+	    if (!check_params (&list, paramcount, params, 5, IICCI,
+			       spec->directives, invalid_reason))
 	      return false;
 	    if (position >= 0)
 	      add_req_type_constraint (&list, position++, FAT_INTEGER);
 	    break;
 
 	  case 'P': case 'p': /* 22.3.8.3 FORMAT-PLURAL */
-	    if (!check_params (&list, paramcount, params, 0, NULL))
+	    if (!check_params (&list, paramcount, params, 0, NULL,
+			       spec->directives, invalid_reason))
 	      return false;
 	    if (colon_p)
 	      {
@@ -2583,14 +2620,16 @@ parse_upto (const char **formatp,
 	    break;
 
 	  case 'C': case 'c': /* 22.3.1.1 FORMAT-CHARACTER */
-	    if (!check_params (&list, paramcount, params, 0, NULL))
+	    if (!check_params (&list, paramcount, params, 0, NULL,
+			       spec->directives, invalid_reason))
 	      return false;
 	    if (position >= 0)
 	      add_req_type_constraint (&list, position++, FAT_CHARACTER);
 	    break;
 
 	  case 'F': case 'f': /* 22.3.3.1 FORMAT-FIXED-FLOAT */
-	    if (!check_params (&list, paramcount, params, 5, IIICC))
+	    if (!check_params (&list, paramcount, params, 5, IIICC,
+			       spec->directives, invalid_reason))
 	      return false;
 	    if (position >= 0)
 	      add_req_type_constraint (&list, position++, FAT_REAL);
@@ -2598,14 +2637,16 @@ parse_upto (const char **formatp,
 
 	  case 'E': case 'e': /* 22.3.3.2 FORMAT-EXPONENTIAL-FLOAT */
 	  case 'G': case 'g': /* 22.3.3.3 FORMAT-GENERAL-FLOAT */
-	    if (!check_params (&list, paramcount, params, 7, IIIICCC))
+	    if (!check_params (&list, paramcount, params, 7, IIIICCC,
+			       spec->directives, invalid_reason))
 	      return false;
 	    if (position >= 0)
 	      add_req_type_constraint (&list, position++, FAT_REAL);
 	    break;
 
 	  case '$': /* 22.3.3.4 FORMAT-DOLLARS-FLOAT */
-	    if (!check_params (&list, paramcount, params, 4, IIIC))
+	    if (!check_params (&list, paramcount, params, 4, IIIC,
+			       spec->directives, invalid_reason))
 	      return false;
 	    if (position >= 0)
 	      add_req_type_constraint (&list, position++, FAT_REAL);
@@ -2616,23 +2657,27 @@ parse_upto (const char **formatp,
 	  case '|': /* 22.3.1.4 FORMAT-PAGE */
 	  case '~': /* 22.3.1.5 FORMAT-TILDE */
 	  case 'I': case 'i': /* 22.3.5.3 */
-	    if (!check_params (&list, paramcount, params, 1, I))
+	    if (!check_params (&list, paramcount, params, 1, I,
+			       spec->directives, invalid_reason))
 	      return false;
 	    break;
 
 	  case '\n': /* 22.3.9.3 #\Newline */
 	  case '_': /* 22.3.5.1 */
-	    if (!check_params (&list, paramcount, params, 0, NULL))
+	    if (!check_params (&list, paramcount, params, 0, NULL,
+			       spec->directives, invalid_reason))
 	      return false;
 	    break;
 
 	  case 'T': case 't': /* 22.3.6.1 FORMAT-TABULATE */
-	    if (!check_params (&list, paramcount, params, 2, II))
+	    if (!check_params (&list, paramcount, params, 2, II,
+			       spec->directives, invalid_reason))
 	      return false;
 	    break;
 
 	  case '*': /* 22.3.7.1 FORMAT-GOTO */
-	    if (!check_params (&list, paramcount, params, 1, I))
+	    if (!check_params (&list, paramcount, params, 1, I,
+			       spec->directives, invalid_reason))
 	      return false;
 	    {
 	      int n; /* value of first parameter */
@@ -2648,7 +2693,12 @@ parse_upto (const char **formatp,
 		  break;
 		}
 	      if (n < 0)
-		return false; /* invalid argument */
+		{
+		  /* invalid argument */
+		  *invalid_reason =
+		    xasprintf (_("In the directive number %u, the argument %d is negative."), spec->directives, n);
+		  return false;
+		}
 	      if (atsign_p)
 		{
 		  /* Absolute goto.  */
@@ -2680,7 +2730,8 @@ parse_upto (const char **formatp,
 	    break;
 
 	  case '?': /* 22.3.7.6 FORMAT-INDIRECTION */
-	    if (!check_params (&list, paramcount, params, 0, NULL))
+	    if (!check_params (&list, paramcount, params, 0, NULL,
+			       spec->directives, invalid_reason))
 	      return false;
 	    if (position >= 0)
 	      add_req_type_constraint (&list, position++, FAT_FORMATSTRING);
@@ -2697,19 +2748,25 @@ parse_upto (const char **formatp,
 	    break;
 
 	  case '/': /* 22.3.5.4 FORMAT-CALL-USER-FUNCTION */
-	    if (!check_params (&list, paramcount, params, 0, NULL))
+	    if (!check_params (&list, paramcount, params, 0, NULL,
+			       spec->directives, invalid_reason))
 	      return false;
 	    if (position >= 0)
 	      add_req_type_constraint (&list, position++, FAT_OBJECT);
 	    while (*format != '\0' && *format != '/')
 	      format++;
 	    if (*format == '\0')
-	      return false;
+	      {
+		*invalid_reason =
+		  xstrdup (_("The string ends in the middle of a ~/.../ directive."));
+		return false;
+	      }
 	    format++;
 	    break;
 
 	  case '(': /* 22.3.8.1 FORMAT-CASE-CONVERSION */
-	    if (!check_params (&list, paramcount, params, 0, NULL))
+	    if (!check_params (&list, paramcount, params, 0, NULL,
+			       spec->directives, invalid_reason))
 	      return false;
 	    *formatp = format;
 	    *positionp = position;
@@ -2717,7 +2774,8 @@ parse_upto (const char **formatp,
 	    *escapep = escape;
 	    {
 	      if (!parse_upto (formatp, positionp, listp, escapep,
-			       NULL, spec, ')', false))
+			       NULL, spec, ')', false,
+			       invalid_reason))
 		return false;
 	    }
 	    format = *formatp;
@@ -2728,8 +2786,13 @@ parse_upto (const char **formatp,
 
 	  case ')': /* 22.3.8.2 FORMAT-CASE-CONVERSION-END */
 	    if (terminator != ')')
-	      return false;
-	    if (!check_params (&list, paramcount, params, 0, NULL))
+	      {
+		*invalid_reason =
+		  xasprintf (_("Found '~%c' without matching '~%c'."), ')', '(');
+		return false;
+	      }
+	    if (!check_params (&list, paramcount, params, 0, NULL,
+			       spec->directives, invalid_reason))
 	      return false;
 	    *formatp = format;
 	    *positionp = position;
@@ -2739,13 +2802,18 @@ parse_upto (const char **formatp,
 
 	  case '[': /* 22.3.7.2 FORMAT-CONDITIONAL */
 	    if (atsign_p && colon_p)
-	      return false;
+	      {
+		*invalid_reason =
+		  xasprintf (_("In the directive number %u, both the @ and the : modifiers are given."), spec->directives);
+		return false;
+	      }
 	    else if (atsign_p)
 	      {
 		struct format_arg_list *nil_list;
 		struct format_arg_list *union_list;
 
-		if (!check_params (&list, paramcount, params, 0, NULL))
+		if (!check_params (&list, paramcount, params, 0, NULL,
+				   spec->directives, invalid_reason))
 		  return false;
 
 		*formatp = format;
@@ -2767,7 +2835,8 @@ parse_upto (const char **formatp,
 		  struct format_arg_list *sub_list =
 		    (list != NULL ? copy_list (list) : NULL);
 		  if (!parse_upto (formatp, &sub_position, &sub_list, escapep,
-				   NULL, spec, ']', false))
+				   NULL, spec, ']', false,
+				   invalid_reason))
 		    return false;
 		  if (sub_list != NULL)
 		    {
@@ -2801,7 +2870,8 @@ parse_upto (const char **formatp,
 		int union_position;
 		struct format_arg_list *union_list;
 
-		if (!check_params (&list, paramcount, params, 0, NULL))
+		if (!check_params (&list, paramcount, params, 0, NULL,
+				   spec->directives, invalid_reason))
 		  return false;
 
 		if (position >= 0)
@@ -2826,10 +2896,15 @@ parse_upto (const char **formatp,
 		      free_list (empty_list);
 		    }
 		  if (!parse_upto (formatp, &sub_position, &sub_list, escapep,
-				   &sub_separator, spec, ']', true))
+				   &sub_separator, spec, ']', true,
+				   invalid_reason))
 		    return false;
 		  if (!sub_separator)
-		    return false;
+		    {
+		      *invalid_reason =
+			xasprintf (_("In the directive number %u, '~:[' is not followed by two clauses, separated by '~;'."), spec->directives);
+		      return false;
+		    }
 		  if (sub_list != NULL)
 		    union_position = sub_position;
 		  union_list = union (union_list, sub_list);
@@ -2841,7 +2916,8 @@ parse_upto (const char **formatp,
 		  struct format_arg_list *sub_list =
 		    (list != NULL ? copy_list (list) : NULL);
 		  if (!parse_upto (formatp, &sub_position, &sub_list, escapep,
-				   NULL, spec, ']', false))
+				   NULL, spec, ']', false,
+				   invalid_reason))
 		    return false;
 		  if (sub_list != NULL)
 		    {
@@ -2869,7 +2945,8 @@ parse_upto (const char **formatp,
 		struct format_arg_list *union_list;
 		bool last_alternative;
 
-		if (!check_params (&list, paramcount, params, 1, I))
+		if (!check_params (&list, paramcount, params, 1, I,
+				   spec->directives, invalid_reason))
 		  return false;
 
 		/* If there was no first parameter, an argument is consumed.  */
@@ -2891,7 +2968,8 @@ parse_upto (const char **formatp,
 		      (list != NULL ? copy_list (list) : NULL);
 		    int sub_separator = 0;
 		    if (!parse_upto (formatp, &sub_position, &sub_list, escapep,
-				     &sub_separator, spec, ']', !last_alternative))
+				     &sub_separator, spec, ']', !last_alternative,
+				     invalid_reason))
 		      return false;
 		    if (sub_list != NULL)
 		      {
@@ -2931,8 +3009,13 @@ parse_upto (const char **formatp,
 
 	  case ']': /* 22.3.7.3 FORMAT-CONDITIONAL-END */
 	    if (terminator != ']')
-	      return false;
-	    if (!check_params (&list, paramcount, params, 0, NULL))
+	      {
+		*invalid_reason =
+		  xasprintf (_("Found '~%c' without matching '~%c'."), ']', '[');
+		return false;
+	      }
+	    if (!check_params (&list, paramcount, params, 0, NULL,
+			       spec->directives, invalid_reason))
 	      return false;
 	    *formatp = format;
 	    *positionp = position;
@@ -2941,7 +3024,8 @@ parse_upto (const char **formatp,
 	    return true;
 
 	  case '{': /* 22.3.7.4 FORMAT-ITERATION */
-	    if (!check_params (&list, paramcount, params, 1, I))
+	    if (!check_params (&list, paramcount, params, 1, I,
+			       spec->directives, invalid_reason))
 	      return false;
 	    *formatp = format;
 	    {
@@ -2952,7 +3036,8 @@ parse_upto (const char **formatp,
 	      sub_spec.directives = 0;
 	      sub_spec.list = sub_list;
 	      if (!parse_upto (formatp, &sub_position, &sub_list, &sub_escape,
-			       NULL, &sub_spec, '}', false))
+			       NULL, &sub_spec, '}', false,
+			       invalid_reason))
 		return false;
 	      spec->directives += sub_spec.directives;
 
@@ -3030,8 +3115,13 @@ parse_upto (const char **formatp,
 
 	  case '}': /* 22.3.7.5 FORMAT-ITERATION-END */
 	    if (terminator != '}')
-	      return false;
-	    if (!check_params (&list, paramcount, params, 0, NULL))
+	      {
+		*invalid_reason =
+		  xasprintf (_("Found '~%c' without matching '~%c'."), '}', '{');
+		return false;
+	      }
+	    if (!check_params (&list, paramcount, params, 0, NULL,
+			       spec->directives, invalid_reason))
 	      return false;
 	    *formatp = format;
 	    *positionp = position;
@@ -3040,7 +3130,8 @@ parse_upto (const char **formatp,
 	    return true;
 
 	  case '<': /* 22.3.6.2, 22.3.5.2 FORMAT-JUSTIFICATION */
-	    if (!check_params (&list, paramcount, params, 4, IIIC))
+	    if (!check_params (&list, paramcount, params, 4, IIIC,
+			       spec->directives, invalid_reason))
 	      return false;
 	    {
 	      struct format_arg_list *sub_escape = NULL;
@@ -3053,7 +3144,8 @@ parse_upto (const char **formatp,
 		{
 		  int sub_separator = 0;
 		  if (!parse_upto (formatp, positionp, listp, &sub_escape,
-				   &sub_separator, spec, '>', true))
+				   &sub_separator, spec, '>', true,
+				   invalid_reason))
 		    return false;
 		  if (!sub_separator)
 		    break;
@@ -3072,8 +3164,13 @@ parse_upto (const char **formatp,
 
 	  case '>': /* 22.3.6.3 FORMAT-JUSTIFICATION-END */
 	    if (terminator != '>')
-	      return false;
-	    if (!check_params (&list, paramcount, params, 0, NULL))
+	      {
+		*invalid_reason =
+		  xasprintf (_("Found '~%c' without matching '~%c'."), '>', '<');
+		return false;
+	      }
+	    if (!check_params (&list, paramcount, params, 0, NULL,
+			       spec->directives, invalid_reason))
 	      return false;
 	    *formatp = format;
 	    *positionp = position;
@@ -3082,7 +3179,8 @@ parse_upto (const char **formatp,
 	    return true;
 
 	  case '^': /* 22.3.9.2 FORMAT-UP-AND-OUT */
-	    if (!check_params (&list, paramcount, params, 3, THREE))
+	    if (!check_params (&list, paramcount, params, 3, THREE,
+			       spec->directives, invalid_reason))
 	      return false;
 	    if (position >= 0 && list != NULL && is_required (list, position))
 	      /* This ~^ can never be executed.  Ignore it.  */
@@ -3100,15 +3198,21 @@ parse_upto (const char **formatp,
 
 	  case ';': /* 22.3.9.1 FORMAT-SEPARATOR */
 	    if (!separator)
-	      return false;
+	      {
+		*invalid_reason =
+		  xasprintf (_("In the directive number %u, '~;' is used in an invalid position."), spec->directives);
+		return false;
+	      }
 	    if (terminator == '>')
 	      {
-		if (!check_params (&list, paramcount, params, 1, I))
+		if (!check_params (&list, paramcount, params, 1, I,
+				   spec->directives, invalid_reason))
 		   return false;
 	      }
 	    else
 	      {
-		if (!check_params (&list, paramcount, params, 0, NULL))
+		if (!check_params (&list, paramcount, params, 0, NULL,
+				   spec->directives, invalid_reason))
 		   return false;
 	      }
 	    *formatp = format;
@@ -3119,7 +3223,8 @@ parse_upto (const char **formatp,
 	    return true;
 
 	  case '!': /* FORMAT-CALL, a CLISP extension */
-	    if (!nocheck_params (&list, paramcount, params))
+	    if (!nocheck_params (&list, paramcount, params,
+				 spec->directives, invalid_reason))
 	      return false;
 	    if (position >= 0)
 	      {
@@ -3129,6 +3234,11 @@ parse_upto (const char **formatp,
 	    break;
 
 	  default:
+	    --format;
+	    *invalid_reason =
+	      (*format == '\0'
+	       ? INVALID_UNTERMINATED_DIRECTIVE ()
+	       : INVALID_CONVERSION_SPECIFIER (spec->directives, *format));
 	    return false;
 	  }
 
@@ -3139,14 +3249,20 @@ parse_upto (const char **formatp,
   *positionp = position;
   *listp = list;
   *escapep = escape;
-  return (terminator == '\0');
+  if (terminator != '\0')
+    {
+      *invalid_reason =
+	xasprintf (_("Found '~%c' without matching '~%c'."), terminator - 1, terminator);
+      return false;
+    }
+  return true;
 }
 
 
 /* ============== Top level format string handling functions ============== */
 
 static void *
-format_parse (const char *format)
+format_parse (const char *format, char **invalid_reason)
 {
   struct spec spec;
   struct spec *result;
@@ -3158,7 +3274,8 @@ format_parse (const char *format)
   escape = NULL;
 
   if (!parse_upto (&format, &position, &spec.list, &escape,
-		   NULL, &spec, '\0', false))
+		   NULL, &spec, '\0', false,
+		   invalid_reason))
     /* Invalid format string.  */
     return NULL;
 
@@ -3166,8 +3283,12 @@ format_parse (const char *format)
   spec.list = union (spec.list, escape);
 
   if (spec.list == NULL)
-    /* Contradictory argument type information.  */
-    return NULL;
+    {
+      /* Contradictory argument type information.  */
+      *invalid_reason =
+	xstrdup (_("The string refers to some argument in incompatible ways."));
+      return NULL;
+    }
 
   /* Normalize the result.  */
   normalize_list (spec.list);
@@ -3253,6 +3374,8 @@ struct formatstring_parser formatstring_lisp =
 
 /* ============================= Testing code ============================= */
 
+#undef union
+
 #ifdef TEST
 
 /* Test program: Print the argument list specification returned by
@@ -3363,16 +3486,26 @@ main ()
   for (;;)
     {
       char *line = NULL;
-      size_t line_len = 0;
+      size_t line_size = 0;
+      int line_len;
+      char *invalid_reason;
       void *descr;
 
-      if (getline (&line, &line_len, stdin) < 0)
+      line_len = getline (&line, &line_size, stdin);
+      if (line_len < 0)
 	break;
+      if (line_len > 0 && line[line_len - 1] == '\n')
+	line[--line_len] = '\0';
+
+      invalid_reason = NULL;
+      descr = format_parse (line, &invalid_reason);
 
-      descr = format_parse (line);
       format_print (descr);
       printf ("\n");
+      if (descr == NULL)
+	printf ("%s\n", invalid_reason);
 
+      free (invalid_reason);
       free (line);
     }
 
diff --git a/gettext-tools/src/format-pascal.c b/gettext-tools/src/format-pascal.c
index cf2d959..f60f8cd 100644
--- a/gettext-tools/src/format-pascal.c
+++ b/gettext-tools/src/format-pascal.c
@@ -1,5 +1,5 @@
 /* Object Pascal format strings.
-   Copyright (C) 2001-2002 Free Software Foundation, Inc.
+   Copyright (C) 2001-2003 Free Software Foundation, Inc.
    Written by Bruno Haible <haible@clisp.cons.org>, 2001.
 
    This program is free software; you can redistribute it and/or modify
@@ -26,6 +26,8 @@
 #include "format.h"
 #include "c-ctype.h"
 #include "xmalloc.h"
+#include "xerror.h"
+#include "format-invalid.h"
 #include "error.h"
 #include "progname.h"
 #include "gettext.h"
@@ -103,7 +105,7 @@ numbered_arg_compare (const void *p1, const void *p2)
 }
 
 static void *
-format_parse (const char *format)
+format_parse (const char *format, char **invalid_reason)
 {
   unsigned int directives;
   unsigned int numbered_arg_count;
@@ -241,6 +243,10 @@ format_parse (const char *format)
 		type = FAT_INTEGER;
 		break;
 	      default:
+		*invalid_reason =
+		  (*format == '\0'
+		   ? INVALID_UNTERMINATED_DIRECTIVE ()
+		   : INVALID_CONVERSION_SPECIFIER (directives, *format));
 		goto bad_format;
 	      }
 
@@ -298,8 +304,14 @@ format_parse (const char *format)
 		     || (type1 == FAT_INTEGER64 && type2 == FAT_INTEGER))
 	      type_both = FAT_INTEGER;
 	    else
-	      /* Incompatible types.  */
-	      type_both = type1, err = true;
+	      {
+		/* Incompatible types.  */
+		type_both = type1;
+		if (!err)
+		  *invalid_reason =
+		    INVALID_INCOMPATIBLE_ARG_TYPES (numbered[i].number);
+		err = true;
+	      }
 
 	    numbered[j-1].type = type_both;
 	  }
@@ -314,6 +326,7 @@ format_parse (const char *format)
 	  }
       numbered_arg_count = j;
       if (err)
+	/* *invalid_reason has already been set above.  */
 	goto bad_format;
     }
 
@@ -510,17 +523,26 @@ main ()
   for (;;)
     {
       char *line = NULL;
-      size_t line_len = 0;
+      size_t line_size = 0;
+      int line_len;
+      char *invalid_reason;
       void *descr;
 
-      if (getline (&line, &line_len, stdin) < 0)
+      line_len = getline (&line, &line_size, stdin);
+      if (line_len < 0)
 	break;
+      if (line_len > 0 && line[line_len - 1] == '\n')
+	line[--line_len] = '\0';
 
-      descr = format_parse (line);
+      invalid_reason = NULL;
+      descr = format_parse (line, &invalid_reason);
 
       format_print (descr);
       printf ("\n");
+      if (descr == NULL)
+	printf ("%s\n", invalid_reason);
 
+      free (invalid_reason);
       free (line);
     }
 
diff --git a/gettext-tools/src/format-php.c b/gettext-tools/src/format-php.c
index d91803b..d0f718f 100644
--- a/gettext-tools/src/format-php.c
+++ b/gettext-tools/src/format-php.c
@@ -1,5 +1,5 @@
 /* PHP format strings.
-   Copyright (C) 2001-2002 Free Software Foundation, Inc.
+   Copyright (C) 2001-2003 Free Software Foundation, Inc.
    Written by Bruno Haible <bruno@clisp.org>, 2002.
 
    This program is free software; you can redistribute it and/or modify
@@ -24,7 +24,10 @@
 #include <stdlib.h>
 
 #include "format.h"
+#include "c-ctype.h"
 #include "xmalloc.h"
+#include "xerror.h"
+#include "format-invalid.h"
 #include "error.h"
 #include "progname.h"
 #include "gettext.h"
@@ -93,7 +96,7 @@ numbered_arg_compare (const void *p1, const void *p2)
 }
 
 static void *
-format_parse (const char *format)
+format_parse (const char *format, char **invalid_reason)
 {
   unsigned int directives;
   unsigned int numbered_arg_count;
@@ -136,7 +139,10 @@ format_parse (const char *format)
 		if (*f == '$')
 		  {
 		    if (m == 0)
-		      goto bad_format;
+		      {
+			*invalid_reason = INVALID_ARGNO_0 (directives);
+			goto bad_format;
+		      }
 		    number = m;
 		    format = ++f;
 		    --unnumbered_arg_count;
@@ -152,7 +158,10 @@ format_parse (const char *format)
 		  {
 		    format++;
 		    if (*format == '\0')
-		      goto bad_format;
+		      {
+			*invalid_reason = INVALID_UNTERMINATED_DIRECTIVE ();
+			goto bad_format;
+		      }
 		    format++;
 		  }
 		else
@@ -201,6 +210,10 @@ format_parse (const char *format)
 		type = FAT_STRING;
 		break;
 	      default:
+		*invalid_reason =
+		  (*format == '\0'
+		   ? INVALID_UNTERMINATED_DIRECTIVE ()
+		   : INVALID_CONVERSION_SPECIFIER (directives, *format));
 		goto bad_format;
 	      }
 
@@ -238,8 +251,14 @@ format_parse (const char *format)
 	    if (type1 == type2)
 	      type_both = type1;
 	    else
-	      /* Incompatible types.  */
-	      type_both = type1, err = true;
+	      {
+		/* Incompatible types.  */
+		type_both = type1;
+		if (!err)
+		  *invalid_reason =
+		    INVALID_INCOMPATIBLE_ARG_TYPES (numbered[i].number);
+		err = true;
+	      }
 
 	    numbered[j-1].type = type_both;
 	  }
@@ -254,6 +273,7 @@ format_parse (const char *format)
 	  }
       numbered_arg_count = j;
       if (err)
+	/* *invalid_reason has already been set above.  */
 	goto bad_format;
     }
 
@@ -447,17 +467,26 @@ main ()
   for (;;)
     {
       char *line = NULL;
-      size_t line_len = 0;
+      size_t line_size = 0;
+      int line_len;
+      char *invalid_reason;
       void *descr;
 
-      if (getline (&line, &line_len, stdin) < 0)
+      line_len = getline (&line, &line_size, stdin);
+      if (line_len < 0)
 	break;
+      if (line_len > 0 && line[line_len - 1] == '\n')
+	line[--line_len] = '\0';
 
-      descr = format_parse (line);
+      invalid_reason = NULL;
+      descr = format_parse (line, &invalid_reason);
 
       format_print (descr);
       printf ("\n");
+      if (descr == NULL)
+	printf ("%s\n", invalid_reason);
 
+      free (invalid_reason);
       free (line);
     }
 
diff --git a/gettext-tools/src/format-python.c b/gettext-tools/src/format-python.c
index 1116a70..3dbc182 100644
--- a/gettext-tools/src/format-python.c
+++ b/gettext-tools/src/format-python.c
@@ -1,5 +1,5 @@
 /* Python format strings.
-   Copyright (C) 2001-2002 Free Software Foundation, Inc.
+   Copyright (C) 2001-2003 Free Software Foundation, Inc.
    Written by Bruno Haible <haible@clisp.cons.org>, 2001.
 
    This program is free software; you can redistribute it and/or modify
@@ -25,7 +25,10 @@
 #include <string.h>
 
 #include "format.h"
+#include "c-ctype.h"
 #include "xmalloc.h"
+#include "xerror.h"
+#include "format-invalid.h"
 #include "error.h"
 #include "progname.h"
 #include "gettext.h"
@@ -108,8 +111,11 @@ named_arg_compare (const void *p1, const void *p2)
 		 ((const struct named_arg *) p2)->name);
 }
 
+#define INVALID_MIXES_NAMED_UNNAMED() \
+  xstrdup (_("The string refers to arguments both through argument names and through unnamed argument specifications."))
+
 static void *
-format_parse (const char *format)
+format_parse (const char *format, char **invalid_reason)
 {
   struct spec spec;
   struct spec *result;
@@ -152,7 +158,10 @@ format_parse (const char *format)
 		  }
 	      }
 	    if (*format == '\0')
-	      goto bad_format;
+	      {
+		*invalid_reason = INVALID_UNTERMINATED_DIRECTIVE ();
+		goto bad_format;
+	      }
 	    name_end = format++;
 
 	    n = name_end - name_start;
@@ -171,7 +180,10 @@ format_parse (const char *format)
 
 	    /* Named and unnamed specifications are exclusive.  */
 	    if (spec.named_arg_count > 0)
-	      goto bad_format;
+	      {
+		*invalid_reason = INVALID_MIXES_NAMED_UNNAMED ();
+		goto bad_format;
+	      }
 
 	    if (spec.allocated == spec.unnamed_arg_count)
 	      {
@@ -196,7 +208,10 @@ format_parse (const char *format)
 
 		/* Named and unnamed specifications are exclusive.  */
 		if (spec.named_arg_count > 0)
-		  goto bad_format;
+		  {
+		    *invalid_reason = INVALID_MIXES_NAMED_UNNAMED ();
+		    goto bad_format;
+		  }
 
 		if (spec.allocated == spec.unnamed_arg_count)
 		  {
@@ -233,6 +248,10 @@ format_parse (const char *format)
 	    type = FAT_FLOAT;
 	    break;
 	  default:
+	    *invalid_reason =
+	      (*format == '\0'
+	       ? INVALID_UNTERMINATED_DIRECTIVE ()
+	       : INVALID_CONVERSION_SPECIFIER (spec.directives, *format));
 	    goto bad_format;
 	  }
 
@@ -242,7 +261,10 @@ format_parse (const char *format)
 
 	    /* Named and unnamed specifications are exclusive.  */
 	    if (spec.unnamed_arg_count > 0)
-	      goto bad_format;
+	      {
+		*invalid_reason = INVALID_MIXES_NAMED_UNNAMED ();
+		goto bad_format;
+	      }
 
 	    if (spec.allocated == spec.named_arg_count)
 	      {
@@ -259,7 +281,10 @@ format_parse (const char *format)
 
 	    /* Named and unnamed specifications are exclusive.  */
 	    if (spec.named_arg_count > 0)
-	      goto bad_format;
+	      {
+		*invalid_reason = INVALID_MIXES_NAMED_UNNAMED ();
+		goto bad_format;
+	      }
 
 	    if (spec.allocated == spec.unnamed_arg_count)
 	      {
@@ -296,8 +321,14 @@ format_parse (const char *format)
 	    else if (type1 == FAT_ANY)
 	      type_both = type2;
 	    else
-	      /* Incompatible types.  */
-	      type_both = FAT_NONE, err = true;
+	      {
+		/* Incompatible types.  */
+		type_both = FAT_NONE;
+		if (!err)
+		  *invalid_reason =
+		    xasprintf (_("The string refers to the argument named '%s' in incompatible ways."), spec.named[i].name);
+		err = true;
+	      }
 
 	    spec.named[j-1].type = type_both;
 	    free (spec.named[i].name);
@@ -313,6 +344,7 @@ format_parse (const char *format)
 	  }
       spec.named_arg_count = j;
       if (err)
+	/* *invalid_reason has already been set above.  */
 	goto bad_format;
     }
 
@@ -609,17 +641,26 @@ main ()
   for (;;)
     {
       char *line = NULL;
-      size_t line_len = 0;
+      size_t line_size = 0;
+      int line_len;
+      char *invalid_reason;
       void *descr;
 
-      if (getline (&line, &line_len, stdin) < 0)
+      line_len = getline (&line, &line_size, stdin);
+      if (line_len < 0)
 	break;
+      if (line_len > 0 && line[line_len - 1] == '\n')
+	line[--line_len] = '\0';
 
-      descr = format_parse (line);
+      invalid_reason = NULL;
+      descr = format_parse (line, &invalid_reason);
 
       format_print (descr);
       printf ("\n");
+      if (descr == NULL)
+	printf ("%s\n", invalid_reason);
 
+      free (invalid_reason);
       free (line);
     }
 
diff --git a/gettext-tools/src/format-tcl.c b/gettext-tools/src/format-tcl.c
index e74126d..0ac982d 100644
--- a/gettext-tools/src/format-tcl.c
+++ b/gettext-tools/src/format-tcl.c
@@ -1,5 +1,5 @@
 /* Tcl format strings.
-   Copyright (C) 2001-2002 Free Software Foundation, Inc.
+   Copyright (C) 2001-2003 Free Software Foundation, Inc.
    Written by Bruno Haible <haible@clisp.cons.org>, 2002.
 
    This program is free software; you can redistribute it and/or modify
@@ -24,7 +24,10 @@
 #include <stdlib.h>
 
 #include "format.h"
+#include "c-ctype.h"
 #include "xmalloc.h"
+#include "xerror.h"
+#include "format-invalid.h"
 #include "error.h"
 #include "progname.h"
 #include "gettext.h"
@@ -97,7 +100,7 @@ numbered_arg_compare (const void *p1, const void *p2)
 }
 
 static void *
-format_parse (const char *format)
+format_parse (const char *format, char **invalid_reason)
 {
   struct spec spec;
   struct spec *result;
@@ -141,13 +144,19 @@ format_parse (const char *format)
 		if (*f == '$')
 		  {
 		    if (m == 0)
-		      goto bad_format;
+		      {
+			*invalid_reason = INVALID_ARGNO_0 (spec.directives);
+			goto bad_format;
+		      }
 		    number = m;
 		    format = ++f;
 
 		    /* Numbered and unnumbered specifications are exclusive.  */
 		    if (seen_unnumbered_arg)
-		      goto bad_format;
+		      {
+			*invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+			goto bad_format;
+		      }
 		    is_numbered_arg = true;
 		    seen_numbered_arg = true;
 		  }
@@ -157,7 +166,10 @@ format_parse (const char *format)
 	    if (!is_numbered_arg)
 	      {
 		if (seen_numbered_arg)
-		  goto bad_format;
+		  {
+		    *invalid_reason = INVALID_MIXES_NUMBERED_UNNUMBERED ();
+		    goto bad_format;
+		  }
 		seen_unnumbered_arg = true;
 	      }
 
@@ -238,6 +250,10 @@ format_parse (const char *format)
 		type = FAT_FLOAT;
 		break;
 	      default:
+		*invalid_reason =
+		  (*format == '\0'
+		   ? INVALID_UNTERMINATED_DIRECTIVE ()
+		   : INVALID_CONVERSION_SPECIFIER (spec.directives, *format));
 		goto bad_format;
 	      }
 
@@ -277,8 +293,14 @@ format_parse (const char *format)
 	    if (type1 == type2)
 	      type_both = type1;
 	    else
-	      /* Incompatible types.  */
-	      type_both = FAT_NONE, err = true;
+	      {
+		/* Incompatible types.  */
+		type_both = FAT_NONE;
+		if (!err)
+		  *invalid_reason =
+		    INVALID_INCOMPATIBLE_ARG_TYPES (spec.numbered[i].number);
+		err = true;
+	      }
 
 	    spec.numbered[j-1].type = type_both;
 	  }
@@ -293,6 +315,7 @@ format_parse (const char *format)
 	  }
       spec.numbered_arg_count = j;
       if (err)
+	/* *invalid_reason has already been set above.  */
 	goto bad_format;
     }
 
@@ -472,7 +495,7 @@ format_print (void *descr)
 	case FAT_SHORT_INTEGER:
 	  printf ("hi");
 	  break;
-	case FAT_UNSIGNED_SHORT_INTEGER:
+	case FAT_SHORT_UNSIGNED_INTEGER:
 	  printf ("[unsigned]hi");
 	  break;
 	case FAT_FLOAT:
@@ -492,17 +515,26 @@ main ()
   for (;;)
     {
       char *line = NULL;
-      size_t line_len = 0;
+      size_t line_size = 0;
+      int line_len;
+      char *invalid_reason;
       void *descr;
 
-      if (getline (&line, &line_len, stdin) < 0)
+      line_len = getline (&line, &line_size, stdin);
+      if (line_len < 0)
 	break;
+      if (line_len > 0 && line[line_len - 1] == '\n')
+	line[--line_len] = '\0';
 
-      descr = format_parse (line);
+      invalid_reason = NULL;
+      descr = format_parse (line, &invalid_reason);
 
       format_print (descr);
       printf ("\n");
+      if (descr == NULL)
+	printf ("%s\n", invalid_reason);
 
+      free (invalid_reason);
       free (line);
     }
 
diff --git a/gettext-tools/src/format-ycp.c b/gettext-tools/src/format-ycp.c
index fd41610..cacab0e 100644
--- a/gettext-tools/src/format-ycp.c
+++ b/gettext-tools/src/format-ycp.c
@@ -1,5 +1,5 @@
 /* YCP and Smalltalk format strings.
-   Copyright (C) 2001-2002 Free Software Foundation, Inc.
+   Copyright (C) 2001-2003 Free Software Foundation, Inc.
    Written by Bruno Haible <haible@clisp.cons.org>, 2001.
 
    This program is free software; you can redistribute it and/or modify
@@ -24,7 +24,10 @@
 #include <stdlib.h>
 
 #include "format.h"
+#include "c-ctype.h"
 #include "xmalloc.h"
+#include "xerror.h"
+#include "format-invalid.h"
 #include "error.h"
 #include "progname.h"
 #include "gettext.h"
@@ -47,7 +50,7 @@ struct spec
 
 
 static void *
-format_parse (const char *format)
+format_parse (const char *format, char **invalid_reason)
 {
   struct spec spec;
   struct spec *result;
@@ -74,7 +77,15 @@ format_parse (const char *format)
 	    format++;
 	  }
 	else
-	  goto bad_format;
+	  {
+	    *invalid_reason =
+	      (*format == '\0'
+	       ? INVALID_UNTERMINATED_DIRECTIVE ()
+	       : (c_isprint (*format)
+		  ? xasprintf (_("In the directive number %u, the character '%c' is not a digit between 1 and 9."), spec.directives, *format)
+		  : xasprintf (_("The character that terminates the directive number %u is not a digit between 1 and 9."), spec.directives)));
+	    goto bad_format;
+	  }
       }
 
   result = (struct spec *) xmalloc (sizeof (struct spec));
@@ -193,17 +204,26 @@ main ()
   for (;;)
     {
       char *line = NULL;
-      size_t line_len = 0;
+      size_t line_size = 0;
+      int line_len;
+      char *invalid_reason;
       void *descr;
 
-      if (getline (&line, &line_len, stdin) < 0)
+      line_len = getline (&line, &line_size, stdin);
+      if (line_len < 0)
 	break;
+      if (line_len > 0 && line[line_len - 1] == '\n')
+	line[--line_len] = '\0';
 
-      descr = format_parse (line);
+      invalid_reason = NULL;
+      descr = format_parse (line, &invalid_reason);
 
       format_print (descr);
       printf ("\n");
+      if (descr == NULL)
+	printf ("%s\n", invalid_reason);
 
+      free (invalid_reason);
       free (line);
     }
 
diff --git a/gettext-tools/src/format.h b/gettext-tools/src/format.h
index 9d2105b..f285721 100644
--- a/gettext-tools/src/format.h
+++ b/gettext-tools/src/format.h
@@ -1,5 +1,5 @@
 /* Format strings.
-   Copyright (C) 2001-2002 Free Software Foundation, Inc.
+   Copyright (C) 2001-2003 Free Software Foundation, Inc.
    Written by Bruno Haible <haible@clisp.cons.org>, 2001.
 
    This program is free software; you can redistribute it and/or modify
@@ -31,8 +31,9 @@ struct formatstring_parser
      Return a freshly allocated structure describing
        1. the argument types/names needed for the format string,
        2. the total number of format directives.
-     Return NULL if the string is not a valid format string.  */
-  void * (*parse) (const char *string);
+     Return NULL if the string is not a valid format string. In this case,
+     also set *invalid_reason to an error message explaining why.  */
+  void * (*parse) (const char *string, char **invalid_reason);
 
   /* Free a format string descriptor, returned by parse().  */
   void (*free) (void *descr);
diff --git a/gettext-tools/src/msgfmt.c b/gettext-tools/src/msgfmt.c
index 9e6a4cd..c43a68a 100644
--- a/gettext-tools/src/msgfmt.c
+++ b/gettext-tools/src/msgfmt.c
@@ -1120,8 +1120,10 @@ check_pair (const char *msgid,
 		arguments that are used by other translations.  */
 
 	  struct formatstring_parser *parser = formatstring_parsers[i];
+	  char *invalid_reason = NULL;
 	  void *msgid_descr =
-	    parser->parse (msgid_plural != NULL ? msgid_plural : msgid);
+	    parser->parse (msgid_plural != NULL ? msgid_plural : msgid,
+			   &invalid_reason);
 
 	  if (msgid_descr != NULL)
 	    {
@@ -1140,7 +1142,7 @@ check_pair (const char *msgid,
 		      pretty_msgstr = buf;
 		    }
 
-		  msgstr_descr = parser->parse (p);
+		  msgstr_descr = parser->parse (p, &invalid_reason);
 
 		  if (msgstr_descr != NULL)
 		    {
@@ -1157,15 +1159,19 @@ check_pair (const char *msgid,
 		      error_at_line (0, 0, msgid_pos->file_name,
 				     msgid_pos->line_number,
 				     _("\
-'%s' is not a valid %s format string, unlike 'msgid'"),
-				     pretty_msgstr, format_language_pretty[i]);
+'%s' is not a valid %s format string, unlike 'msgid'. Reason: %s"),
+				     pretty_msgstr, format_language_pretty[i],
+				     invalid_reason);
 		      error_with_progname = true;
 		      exit_status = EXIT_FAILURE;
+		      free (invalid_reason);
 		    }
 		}
 
 	      parser->free (msgid_descr);
 	    }
+	  else
+	    free (invalid_reason);
 	}
 
   if (check_accelerators && msgid_plural == NULL)
diff --git a/gettext-tools/src/msgmerge.c b/gettext-tools/src/msgmerge.c
index 87bd713..41c51e0 100644
--- a/gettext-tools/src/msgmerge.c
+++ b/gettext-tools/src/msgmerge.c
@@ -513,8 +513,10 @@ msgfmt_check_pair_fails (const lex_pos_ty *pos,
 {
   bool failure;
   struct formatstring_parser *parser = formatstring_parsers[fmt];
+  char *invalid_reason = NULL;
   void *msgid_descr =
-    parser->parse (msgid_plural != NULL ? msgid_plural : msgid);
+    parser->parse (msgid_plural != NULL ? msgid_plural : msgid,
+		   &invalid_reason);
 
   failure = false;
   if (msgid_descr != NULL)
@@ -524,7 +526,7 @@ msgfmt_check_pair_fails (const lex_pos_ty *pos,
 
       for (p = msgstr; p < p_end; p += strlen (p) + 1)
 	{
-	  void *msgstr_descr = parser->parse (msgstr);
+	  void *msgstr_descr = parser->parse (msgstr, &invalid_reason);
 
 	  if (msgstr_descr != NULL)
 	    {
@@ -533,7 +535,10 @@ msgfmt_check_pair_fails (const lex_pos_ty *pos,
 	      parser->free (msgstr_descr);
 	    }
 	  else
-	    failure = true;
+	    {
+	      failure = true;
+	      free (invalid_reason);
+	    }
 
 	  if (failure)
 	    break;
@@ -541,6 +546,8 @@ msgfmt_check_pair_fails (const lex_pos_ty *pos,
 
       parser->free (msgid_descr);
     }
+  else
+    free (invalid_reason);
 
   return failure;
 }
diff --git a/gettext-tools/src/xgettext.c b/gettext-tools/src/xgettext.c
index e3a3861..e1706a7 100644
--- a/gettext-tools/src/xgettext.c
+++ b/gettext-tools/src/xgettext.c
@@ -1142,7 +1142,8 @@ meta information, not the empty string.\n")));
 	  && formatstring_parsers[i] == current_formatstring_parser)
 	{
 	  struct formatstring_parser *parser = formatstring_parsers[i];
-	  void *descr = parser->parse (mp->msgid);
+	  char *invalid_reason = NULL;
+	  void *descr = parser->parse (mp->msgid, &invalid_reason);
 
 	  if (descr != NULL)
 	    {
@@ -1160,8 +1161,11 @@ meta information, not the empty string.\n")));
 	      parser->free (descr);
 	    }
 	  else
-	    /* msgid is not a valid format string.  */
-	    is_format[i] = impossible;
+	    {
+	      /* msgid is not a valid format string.  */
+	      is_format[i] = impossible;
+	      free (invalid_reason);
+	    }
 	}
       mp->is_format[i] = is_format[i];
     }
@@ -1226,7 +1230,8 @@ remember_a_message_plural (message_ty *mp, char *string, lex_pos_ty *pos)
 	    && (mp->is_format[i] == undecided || mp->is_format[i] == possible))
 	  {
 	    struct formatstring_parser *parser = formatstring_parsers[i];
-	    void *descr = parser->parse (mp->msgid_plural);
+	    char *invalid_reason = NULL;
+	    void *descr = parser->parse (mp->msgid_plural, &invalid_reason);
 
 	    if (descr != NULL)
 	      {
@@ -1237,8 +1242,11 @@ remember_a_message_plural (message_ty *mp, char *string, lex_pos_ty *pos)
 		parser->free (descr);
 	      }
 	    else
-	      /* msgid_plural is not a valid format string.  */
-	      mp->is_format[i] = impossible;
+	      {
+		/* msgid_plural is not a valid format string.  */
+		mp->is_format[i] = impossible;
+		free (invalid_reason);
+	      }
 	  }
     }
   else