ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | Fri May 13 00:16:30 2022 +0200| [a78173374a897e659b16a53b0a04a7ed550a0e32] | committer: Andreas Rheinhardt ffbuild/common: Fix CPPFLAGS applied for compiling C++ files Currently, $(CPPFLAGS) and $(CFLAGS) are prepended to CXXFLAGS (the flags for compiling C++) like this: CXXFLAGS := $(CPPFLAGS) $(CFLAGS) $(CXXFLAGS) Using ":=" creates a simply expanded variable, i.e. the values of the variable at the time of assignment are used and later modifications to them are ignored (using a recursively expanding variable (i.e. "=" instead of ":=") is not really possible here, as there would be an infinite loop when evaluating CXXFLAGS). Yet we perform later additions to CPPFLAGS: HAVE_AV_CONFIG_H and BUILDING_libfoo are defined. These do not reach C++ compilations. To fix this a trick is employed to prepend to a recursively expanded variable while keeping it recursively expanded. There are two practical consequences of this: C++ files now no longer include the version.h header, but only the version_major.h header of their library, saving some recompilations. Furthermore, they now get some optimized math functions (namely the ones from lavu/intmath.h instead of the ones from lavu/common.h). (av_parity() is the only one for which it makes a difference.) Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=a78173374a897e659b...

ffbuild/common.mak | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/ffbuild/common.mak b/ffbuild/common.mak index 24113c59eb..f52473453e 100644 --- a/ffbuild/common.mak +++ b/ffbuild/common.mak @@ -29,6 +29,9 @@ $(foreach VAR,$(SILENT),$(eval override $(VAR) = @$($(VAR)))) $(eval INSTALL = @$(call ECHO,INSTALL,$$(^:$(SRC_DIR)/%=%)); $(INSTALL)) endif +# Prepend to a recursively expanded variable without making it simply expanded. +PREPEND = $(eval $(1) = $(patsubst %,$$(%), $(2)) $(value $(1))) + # NASM requires -I path terminated with / IFLAGS := -I. -I$(SRC_LINK)/ CPPFLAGS := $(IFLAGS) $(CPPFLAGS) @@ -37,7 +40,9 @@ CCFLAGS = $(CPPFLAGS) $(CFLAGS) OBJCFLAGS += $(EOBJCFLAGS) OBJCCFLAGS = $(CPPFLAGS) $(CFLAGS) $(OBJCFLAGS) ASFLAGS := $(CPPFLAGS) $(ASFLAGS) -CXXFLAGS := $(CPPFLAGS) $(CFLAGS) $(CXXFLAGS) +# Use PREPEND here so that later (target-dependent) additions to CPPFLAGS +# end up in CXXFLAGS. +$(call PREPEND,CXXFLAGS, CPPFLAGS CFLAGS) X86ASMFLAGS += $(IFLAGS:%=%/) -I$(<D)/ -Pconfig.asm HOSTCCFLAGS = $(IFLAGS) $(HOSTCPPFLAGS) $(HOSTCFLAGS)