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build: Use Make builtin for .objs response files when possible

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Since 9e857e1f8a, library.mak generates a
response file containing the list of input object files. This was done
to avoid hitting the 8192 character command line limit on Windows
shells.

However, that particular solution still relies on emitting a
very long `echo` command that gets delegated to a subshell. This means
that, for example, running `make` within problematic shells like Git
Bash could still hit the command line length limit when this `echo` step
is ran. Other MSYS2 shells are not affected, meaning the previous
workaround only helped when running in an MSYS2 environment, but broke
when using Git Bash, e.g. for MSVC. This primarily affected `libavcodec`
due to the sheer volume of files contained within.

To avoid this problem, this commit changes the object emission step to
use GNU make's `file` builtin to write the list of object files. `file`
itself was introduced in GNU Make 4.0, but FFmpeg still supports old
versions--notably Apple's ancient Make 3.81--so for older make versions
that don't support this, the old echo subshell is used. This tradeoff
should be fine since it's trivial to grab a new-enough Make on Windows,
and other platforms that may be stuck with ancient Make versions
shouldn't have nearly as restrictive command line limits.

Signed-off-by: crueter <crueter@eden-emu.dev>
This commit is contained in:
crueter
2026-05-25 01:19:29 -04:00
committed by Martin Storsjö
parent dc953a19e6
commit 4ba56d8ab7
1 changed files with 18 additions and 0 deletions
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18
ffbuild/library.mak
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@@ -14,6 +14,15 @@ INSTHEADERS := $(INSTHEADERS) $(HEADERS:%=$(SUBDIR)%)
all-$(CONFIG_STATIC): $(SUBDIR)$(LIBNAME) $(SUBDIR)lib$(FULLNAME).pc
all-$(CONFIG_SHARED): $(SUBDIR)$(SLIBNAME) $(SUBDIR)lib$(FULLNAME).pc
# Make <4.0 does not support the built-in file function;
# versions that do support it should use it, as it's
# faster and isn't bound by command line length limits.
ifeq (4.0,$(firstword $(sort 4.0 $(MAKE_VERSION))))
HAVE_BUILTIN_FILE := yes
else
HAVE_BUILTIN_FILE := no
endif
LIBOBJS := $(OBJS) $(SHLIBOBJS) $(STLIBOBJS) $(SUBDIR)%.h.o $(TESTOBJS)
$(LIBOBJS) $(LIBOBJS:.o=.s) $(LIBOBJS:.o=.i): CPPFLAGS += -DHAVE_AV_CONFIG_H
@@ -36,7 +45,11 @@ endif
$(SUBDIR)$(LIBNAME): $(OBJS) $(STLIBOBJS)
$(RM) $@
ifeq ($(RESPONSE_FILES),yes)
ifeq ($(HAVE_BUILTIN_FILE),yes)
$(file >$@.objs,$^)
else
$(Q)echo $^ > $@.objs
endif
$(AR) $(ARFLAGS) $(AR_O) @$@.objs
else
$(AR) $(ARFLAGS) $(AR_O) $^
@@ -75,7 +88,12 @@ $(SUBDIR)$(SLIBNAME): $(SUBDIR)$(SLIBNAME_WITH_MAJOR)
$(SUBDIR)$(SLIBNAME_WITH_MAJOR): $(OBJS) $(SHLIBOBJS) $(SUBDIR)lib$(NAME).ver
$(SLIB_CREATE_DEF_CMD)
ifeq ($(RESPONSE_FILES),yes)
ifeq ($(HAVE_BUILTIN_FILE),yes)
$$(file >$$@.objs,$$(filter %.o,$$^))
else
$(Q)echo $$(filter %.o,$$^) > $$@.objs
endif
$$(call LINK,$$(call $(NAME)LINK_SO_ARGS) $$(LD_O) @$$@.objs $$(call $(NAME)LINK_EXTRA))
else
$$(call LINK,$$(call $(NAME)LINK_SO_ARGS) $$(LD_O) $$(filter %.o,$$^) $$(call $(NAME)LINK_EXTRA))