[FFmpeg-devel] build for Android on WIndows

[Alex Cohn]

When we build ffmpeg for Android in Windows (using cygwin or Mingw
shell), and enable NEON, make for libavcodec fails because the LD and
AR command lines become too long.

I suggest a simple patch which is not cygwin dependent. I am not sure
if this patch will resolve all problems for everybody.

diff --git a/library.mak b/library.mak
index cd39f11..88ad0a4 100644
--- a/library.mak
+++ b/library.mak
@@ -33,7 +33,8 @@ $(TESTOBJS) $(TESTOBJS:.o=.i): CPPFLAGS += -DTEST

 $(SUBDIR)$(LIBNAME): $(OBJS)
        $(RM) $@
-       $(AR) $(ARFLAGS) $(AR_O) $^
+       $(AR) $(ARFLAGS) $(AR_O) $(wordlist 1,400,$^)
+       $(AR) $(ARFLAGS) $(AR_O) $(wordlist 401,999,$^)
        $(RANLIB) $@

 install-headers: install-lib$(NAME)-headers install-lib$(NAME)-pkgconfig
@@ -53,7 +54,10 @@ $(SUBDIR)$(SLIBNAME): $(SUBDIR)$(SLIBNAME_WITH_MAJOR)

 $(SUBDIR)$(SLIBNAME_WITH_MAJOR): $(OBJS) $(SLIBOBJS) $(SUBDIR)lib$(NAME).ver
        $(SLIB_CREATE_DEF_CMD)
-       $$(LD) $(SHFLAGS) $(LDFLAGS) $$(LD_O) $$(filter %.o,$$^) $(FFEXTRALIBS)
+       $(Q)echo >$(SUBDIR)lib$(NAME).list $(wordlist 1,400,$(filter %.o,$$<))
+       $(Q)echo >>$(SUBDIR)lib$(NAME).list $(wordlist 401,999,$(filter %.o,$$<)
+       $$(LD) $(SHFLAGS) $(LDFLAGS) $$(LD_O)
@$(SUBDIR)lib$(NAME).list $(FFEXTRALIBS)
+       -$(RM) $(SUBDIR)lib$(NAME).list
        $(SLIB_EXTRA_CMD)

 ifdef SUBDIR

See http://stackoverflow.com/questions/23683518/how-to-compile-ffmpeg-2-2-2-on-windows-with-cygwin-and-android-ndk-r9c

I propose this patch with a grain of doubt. On one hand, I am not sure
if all supported toolchains handle the LD @response syntax, exactly
the same way as gcc does. On the other hand, I left aside the similar
problem for `make clean`, because I could not verify all scenarios
that can happen with `make clean`. Also, using $(wordlist) is an ugly
hack, but unfortunately `make.exe` v.3.81 that ships with Android NDK
r9d still does not support $(file) function.

BR,
Alex Cohn