[FFmpeg-devel] [PATCH 1/3] configure: Force mingw's ld to keep the reloc section

[Alex Smith]

From: Alex Smith <alex.smith at warpsharp.info>

Binutils will always strip the relocation information from executable
files even if it needs it (dynamicbase/ASLR).  We can work around this
by using the pic-executable flag combined with setting the correct entry
point since apparently ld forgets what that should be.  This problem
affects both 32 and 64-bit mingw-w64.

We can combine the nxcompat/dynamicbase check because they were added to
binutils at the same time.

Signed-off-by: Alex Smith <alex.smith at warpsharp.info>

Conflicts:
	configure
---
 configure | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index d2a25bb..d6ab35a 100755
--- a/configure
+++ b/configure
@@ -4367,8 +4367,6 @@ case $target_os in
             LIBTARGET=arm-wince
         fi
         enabled shared && ! enabled small && check_cmd $windres --version && enable gnu_windres
-        check_ldflags -Wl,--nxcompat
-        check_ldflags -Wl,--dynamicbase
         enabled x86_32 && check_ldflags -Wl,--large-address-aware
         shlibdir_default="$bindir_default"
         SLIBPREF=""
@@ -4392,6 +4390,17 @@ case $target_os in
         objformat="win32"
         ranlib=:
         enable dos_paths
+        check_ldflags -Wl,--nxcompat,--dynamicbase
+        # Lets work around some stupidity in binutils.
+        # ld will strip relocations from executables even though we need them
+        # for dynamicbase (ASLR).  Using -pie does retain the reloc section
+        # however ld then forgets what the entry point should be (oops) so we
+        # have to manually (re)set it.
+        if enabled x86_32; then
+            add_ldexeflags -Wl,--pic-executable,-e,_mainCRTStartup
+        elif enabled x86_64; then
+            add_ldexeflags -Wl,--pic-executable,-e,mainCRTStartup
+        fi
         ;;
     win32|win64)
         disable symver
-- 
1.9.5.msysgit.0