Allow static C++ destructors to be properly called on dlclose().

With this patch, _and_ an upcoming build/ patch, the destruction
of static C++ objects contained in shared libraries will happen
properly when dlclose() is called.

Note that this change introduces crtbegin_so.S and crtend_so.S which
are currently ignored by the build system.

+ move definition of __dso_handle to the right place
  (before that, all shared libraries used the __dso_handle
   global variable from the C library).

  Note that we keep a 'weak' __dso_handle in aeabi.c to avoid
  breaking the build until the next patch to build/core/combo/
  appears. We will be able to remove that later.

+ move bionic/aeabi.c to arch-arm/bionic/ (its proper location)

Change-Id: Ie771aa204e3acbdf02fd30ebd4150373a1398f39
NOTE: The NDK will need to be modified to enable this feature in
      the shared libraries that are generated through it.

3 files changed, 13 insertions, 7 deletions

diff --git a/libc/arch-x86/bionic/crtbegin_dynamic.S b/libc/arch-x86/bionic/crtbegin_dynamic.S
index 3b47b18..88e7e6a 100644
--- a/libc/arch-x86/bionic/crtbegin_dynamic.S
+++ b/libc/arch-x86/bionic/crtbegin_dynamic.S
@@ -30,7 +30,7 @@
 	.globl _start
 
 # this is the small startup code that is first run when
-# any executable that is statically-linked with Bionic
+# any executable that is dynamically-linked with Bionic
 # runs.
 #
 # it's purpose is to call __libc_init with appropriate
@@ -94,3 +94,4 @@ __FINI_ARRAY__:
 __CTOR_LIST__:
 	.long -1
 
+#include "__dso_handle.S"
diff --git a/libc/arch-x86/bionic/crtbegin_so.S b/libc/arch-x86/bionic/crtbegin_so.S
index d49e9df..d879fef 100644
--- a/libc/arch-x86/bionic/crtbegin_so.S
+++ b/libc/arch-x86/bionic/crtbegin_so.S
@@ -1,3 +1,10 @@
+# This function is to be called when the shared library
+# is unloaded through dlclose()
+_on_dlclose:
+    lea __dso_handle, %eax
+    call __cxa_finalize
+    ret
+
 /* we put the _init() function here in case the user files for the shared
  * libs want to drop things into .init section.
  * We then will call our ctors from crtend_so.o */
@@ -20,6 +27,7 @@ __INIT_ARRAY__:
 .globl __FINI_ARRAY__
 __FINI_ARRAY__:
     .long -1
+    .long _on_dlclose
 
 .section .ctors, "aw"
 .align 4
@@ -27,3 +35,5 @@ __FINI_ARRAY__:
 .globl __CTOR_LIST__
 __CTOR_LIST__:
         .long -1
+
+#include "__dso_handle.S"
diff --git a/libc/arch-x86/bionic/crtbegin_static.S b/libc/arch-x86/bionic/crtbegin_static.S
index eb4acee..3f8446e 100644
--- a/libc/arch-x86/bionic/crtbegin_static.S
+++ b/libc/arch-x86/bionic/crtbegin_static.S
@@ -67,12 +67,6 @@ _start:
     .long   __FINI_ARRAY__
     .long   __CTOR_LIST__
 
-# the .ctors section contains a list of pointers to "constructor"
-# functions that need to be called in order during C library initialization,
-# just before the program is being run. This is a C++ requirement
-#
-# the last entry shall be 0, and is defined in crtend.S
-#
 	.section .preinit_array, "aw"
 	.globl __PREINIT_ARRAY__
 __PREINIT_ARRAY__:
@@ -93,3 +87,4 @@ __FINI_ARRAY__:
 __CTOR_LIST__:
 	.long -1
 
+#include "__dso_handle.S"