linux: turn on -Wextra

This is a followup to an earlier change (r38266) which did most of the
warning-related cleanup.  This one just flips the flag, and fixes some
new warnings that crept in during the window while the flag was off.

Second try, now with some libpng fixes.

BUG=34160

Review URL: http://codereview.chromium.org/1320011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@42700 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 52 insertions, 48 deletions

diff --git a/gfx/codec/png_codec.cc b/gfx/codec/png_codec.cc
index eaf94f0..9db0095 100644
--- a/gfx/codec/png_codec.cc
+++ b/gfx/codec/png_codec.cc
@@ -541,21 +541,53 @@ void ConvertBGRAtoRGB(const unsigned char* bgra, int pixel_width,
   }
 }
 
-// Automatically destroys the given write structs on destruction to make
-// cleanup and error handling code cleaner.
-class PngWriteStructDestroyer {
- public:
-  PngWriteStructDestroyer(png_struct** ps, png_info** pi) : ps_(ps), pi_(pi) {
-  }
-  ~PngWriteStructDestroyer() {
-    png_destroy_write_struct(ps_, pi_);
+// The type of functions usable for converting between pixel formats.
+typedef void (*FormatConverter)(const unsigned char* in, int w,
+                                unsigned char* out, bool* is_opaque);
+
+// libpng uses a wacky setjmp-based API, which makes the compiler nervous.
+// We constrain all of the calls we make to libpng where the setjmp() is in
+// place to this function.
+// Returns true on success.
+bool DoLibpngWrite(png_struct* png_ptr, png_info* info_ptr,
+                   PngEncoderState* state,
+                   int width, int height, int row_byte_width,
+                   const unsigned char* input,
+                   int png_output_color_type, int output_color_components,
+                   FormatConverter converter) {
+  // Make sure to not declare any locals here -- locals in the presence
+  // of setjmp() in C++ code makes gcc complain.
+
+  if (setjmp(png_jmpbuf(png_ptr)))
+    return false;
+
+  // Set our callback for libpng to give us the data.
+  png_set_write_fn(png_ptr, state, EncoderWriteCallback, NULL);
+
+  png_set_IHDR(png_ptr, info_ptr, width, height, 8, png_output_color_type,
+               PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
+               PNG_FILTER_TYPE_DEFAULT);
+  png_write_info(png_ptr, info_ptr);
+
+  if (!converter) {
+    // No conversion needed, give the data directly to libpng.
+    for (int y = 0; y < height; y ++) {
+      png_write_row(png_ptr,
+                    const_cast<unsigned char*>(&input[y * row_byte_width]));
+    }
+  } else {
+    // Needs conversion using a separate buffer.
+    unsigned char* row = new unsigned char[width * output_color_components];
+    for (int y = 0; y < height; y ++) {
+      converter(&input[y * row_byte_width], width, row, NULL);
+      png_write_row(png_ptr, row);
+    }
+    delete[] row;
   }
- private:
-  png_struct** ps_;
-  png_info** pi_;
 
-  DISALLOW_EVIL_CONSTRUCTORS(PngWriteStructDestroyer);
-};
+  png_write_end(png_ptr, info_ptr);
+  return true;
+}
 
 }  // namespace
 
@@ -566,8 +598,7 @@ bool PNGCodec::Encode(const unsigned char* input, ColorFormat format,
                       std::vector<unsigned char>* output) {
   // Run to convert an input row into the output row format, NULL means no
   // conversion is necessary.
-  void (*converter)(const unsigned char* in, int w, unsigned char* out,
-                    bool* is_opaque) = NULL;
+  FormatConverter converter = NULL;
 
   int input_color_components, output_color_components;
   int png_output_color_type;
@@ -635,42 +666,15 @@ bool PNGCodec::Encode(const unsigned char* input, ColorFormat format,
     png_destroy_write_struct(&png_ptr, NULL);
     return false;
   }
-  PngWriteStructDestroyer destroyer(&png_ptr, &info_ptr);
-
-  if (setjmp(png_jmpbuf(png_ptr))) {
-    // The destroyer will ensure that the structures are cleaned up in this
-    // case, even though we may get here as a jump from random parts of the
-    // PNG library called below.
-    return false;
-  }
 
-  // Set our callback for libpng to give us the data.
   PngEncoderState state(output);
-  png_set_write_fn(png_ptr, &state, EncoderWriteCallback, NULL);
+  bool success = DoLibpngWrite(png_ptr, info_ptr, &state,
+                               w, h, row_byte_width, input,
+                               png_output_color_type, output_color_components,
+                               converter);
+  png_destroy_write_struct(&png_ptr, &info_ptr);
 
-  png_set_IHDR(png_ptr, info_ptr, w, h, 8, png_output_color_type,
-               PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
-               PNG_FILTER_TYPE_DEFAULT);
-  png_write_info(png_ptr, info_ptr);
-
-  if (!converter) {
-    // No conversion needed, give the data directly to libpng.
-    for (int y = 0; y < h; y ++) {
-      png_write_row(png_ptr,
-                    const_cast<unsigned char*>(&input[y * row_byte_width]));
-    }
-  } else {
-    // Needs conversion using a separate buffer.
-    unsigned char* row = new unsigned char[w * output_color_components];
-    for (int y = 0; y < h; y ++) {
-      converter(&input[y * row_byte_width], w, row, NULL);
-      png_write_row(png_ptr, row);
-    }
-    delete[] row;
-  }
-
-  png_write_end(png_ptr, info_ptr);
-  return true;
+  return success;
 }
 
 // static