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| author | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | 2022-05-13 00:16:30 +0200 |
|---|---|---|
| committer | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | 2022-05-24 21:30:52 +0200 |
| commit | a78173374a897e659b16a53b0a04a7ed550a0e32 (patch) | |
| tree | 87bd14bb5c995d2a3939772338a08d0488d90eaf /ffbuild | |
| parent | b033913d1c5998a29dfd13e9906dd707ff6eff12 (diff) | |
| download | ffmpeg-a78173374a897e659b16a53b0a04a7ed550a0e32.tar.gz | |
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>
Diffstat (limited to 'ffbuild')
| -rw-r--r-- | ffbuild/common.mak | 7 |
1 files changed, 6 insertions, 1 deletions
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) |