From 1dbeeca5c43cdbf060a11a156a3b6e4ddc45b3f0 Mon Sep 17 00:00:00 2001
From: David 'Digit' Turner <digit@google.com>
Date: Thu, 24 Sep 2009 15:48:44 -0700
Subject: [PATCH] Fix NDK usage of libgcc.a when building shared libraries

The main idea is that libgcc.a should appear after object files and
static libraries but before depending shared libraries. This willl
force the linker to copy the libgcc.a functions required by the
generated library into the target binary, instead of relying on
what's available in libc.so and others.

This ensures maximum portability, and prevent problems in the future
when we change the toolchain, which translates to different libgcc.a
functions embedded in libc.so and other exposed native libraries.

However, this will make also generated shared libraries bigger, because
the compiler insists on generating code that depends on a bunch of C++
support functions (even when building from C sources). An increase of
about 8KB per shared library is expected.
---
 ndk/build/toolchains/arm-eabi-4.2.1/setup.mk | 15 +++++++++++++--
 ndk/docs/CHANGES.TXT                         | 10 +++++++++-
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/ndk/build/toolchains/arm-eabi-4.2.1/setup.mk b/ndk/build/toolchains/arm-eabi-4.2.1/setup.mk
index 4c10c07bd..f5ca8b45e 100644
--- a/ndk/build/toolchains/arm-eabi-4.2.1/setup.mk
+++ b/ndk/build/toolchains/arm-eabi-4.2.1/setup.mk
@@ -74,7 +74,7 @@ TARGET_AR      := $(TOOLCHAIN_PREFIX)ar
 TARGET_ARFLAGS := crs
 
 TARGET_LIBGCC := $(shell $(TARGET_CC) -mthumb-interwork -print-libgcc-file-name)
-TARGET_LDLIBS := -Wl,-rpath-link=$(SYSROOT)/usr/lib $(TARGET_LIBGCC)
+TARGET_LDLIBS := -Wl,-rpath-link=$(SYSROOT)/usr/lib
 
 # These flags are used to ensure that a binary doesn't reference undefined
 # flags.
@@ -84,6 +84,15 @@ TARGET_NO_UNDEFINED_LDFLAGS := -Wl,--no-undefined
 # this toolchain's generated binaries
 TARGET_ABI_SUBDIR := armeabi
 
+# NOTE: Ensure that TARGET_LIBGCC is placed after all private objects
+#       and static libraries, but before any other library in the link
+#       command line when generating shared libraries and executables.
+#
+#       This ensures that all libgcc.a functions required by the target
+#       will be included into it, instead of relying on what's available
+#       on other libraries like libc.so, which may change between system
+#       releases due to toolchain or library changes.
+#
 define cmd-build-shared-library
 $(TARGET_CC) \
     -nostdlib -Wl,-soname,$(notdir $@) \
@@ -93,6 +102,7 @@ $(TARGET_CC) \
     $(PRIVATE_WHOLE_STATIC_LIBRARIES) \
     -Wl,--no-whole-archive \
     $(PRIVATE_STATIC_LIBRARIES) \
+    $(TARGET_LIBGCC) \
     $(PRIVATE_SHARED_LIBRARIES) \
     $(PRIVATE_LDFLAGS) \
     $(PRIVATE_LDLIBS) \
@@ -105,10 +115,11 @@ $(TARGET_CC) \
     -Wl,-dynamic-linker,/system/bin/linker \
     -Wl,--gc-sections \
     -Wl,-z,nocopyreloc \
-    $(PRIVATE_SHARED_LIBRARIES) \
     $(TARGET_CRTBEGIN_DYNAMIC_O) \
     $(PRIVATE_OBJECTS) \
     $(PRIVATE_STATIC_LIBRARIES) \
+    $(TARGET_LIBGCC) \
+    $(PRIVATE_SHARED_LIBRARIES) \
     $(PRIVATE_LDFLAGS) \
     $(PRIVATE_LDLIBS) \
     $(TARGET_CRTEND_O) \
diff --git a/ndk/docs/CHANGES.TXT b/ndk/docs/CHANGES.TXT
index faad11db8..c03fc6093 100644
--- a/ndk/docs/CHANGES.TXT
+++ b/ndk/docs/CHANGES.TXT
@@ -1,5 +1,13 @@
 Android NDK ChangeLog:
 
+-------------------------------------------------------------------------------
+current version
+
+IMPORTANT BUG FIXES:
+
+- Make target shared libraries portable to systems that don't use the exact same
+  toolchain (GCC 4.2.1) .
+
 -------------------------------------------------------------------------------
 android-ndk-1.6_r1
 
@@ -24,7 +32,7 @@ IMPORTANT BUG FIXES:
   in $(CLEAR_VARS) script.
 
 
-IMPORTANT CHANGES
+IMPORTANT CHANGES:
 
 - The 'sources' directory is gone. The NDK build system now looks for
   $(APP_PROJECT_PATH)/jni/Android.mk by default. You can override this with