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Makefile: lazily compute header dependencies
Use the gcc -MMD -MP -MF options to generate dependency rules as a byproduct when building .o files if the COMPUTE_HEADER_DEPENDENCIES variable is defined. That variable is left undefined by default for now. As each object file is built, write a makefile fragment containing its dependencies in the deps/ subdirectory of its containing directory. The deps/ directories should be generated if they are missing at the start of each build. So let each object file depend on $(missing_dep_dirs), which lists only the directories of this kind that are missing to avoid needlessly regenerating files when the directories' timestamps change. gcc learned the -MMD -MP -MF options in version 3.0, so most gcc users should have them by now. The dependencies this option computes are more specific than the rough estimates hard-coded in the Makefile, greatly speeding up rebuilds when only a little-used header file has changed. Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
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1
.gitignore
vendored
1
.gitignore
vendored
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@ -177,6 +177,7 @@
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*.exe
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*.[aos]
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*.py[co]
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*.o.d
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*+
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/config.mak
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/autom4te.cache
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49
Makefile
49
Makefile
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@ -217,6 +217,10 @@ all::
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# DEFAULT_EDITOR='~/bin/vi',
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# DEFAULT_EDITOR='$GIT_FALLBACK_EDITOR',
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# DEFAULT_EDITOR='"C:\Program Files\Vim\gvim.exe" --nofork'
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#
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# Define COMPUTE_HEADER_DEPENDENCIES if your compiler supports the -MMD option
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# and you want to avoid rebuilding objects when an unrelated header file
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# changes.
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GIT-VERSION-FILE: FORCE
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@$(SHELL_PATH) ./GIT-VERSION-GEN
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@ -1677,14 +1681,48 @@ ASM_SRC := $(wildcard $(OBJECTS:o=S))
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ASM_OBJ := $(ASM_SRC:S=o)
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C_OBJ := $(filter-out $(ASM_OBJ),$(OBJECTS))
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ifdef COMPUTE_HEADER_DEPENDENCIES
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dep_dirs := $(addsuffix deps,$(sort $(dir $(OBJECTS))))
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$(dep_dirs):
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mkdir -p $@
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missing_dep_dirs := $(filter-out $(wildcard $(dep_dirs)),$(dep_dirs))
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else
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dep_dirs =
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missing_dep_dirs =
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endif
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.SUFFIXES:
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$(C_OBJ): %.o: %.c GIT-CFLAGS
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$(QUIET_CC)$(CC) -o $*.o -c $(ALL_CFLAGS) $<
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$(C_OBJ): %.o: %.c GIT-CFLAGS $(missing_dep_dirs)
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$(QUIET_CC)$(CC) -o $*.o -c $(dep_args) $(ALL_CFLAGS) $<
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%.s: %.c GIT-CFLAGS FORCE
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$(QUIET_CC)$(CC) -S $(ALL_CFLAGS) $<
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$(ASM_OBJ): %.o: %.S GIT-CFLAGS
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$(QUIET_CC)$(CC) -o $*.o -c $(ALL_CFLAGS) $<
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$(ASM_OBJ): %.o: %.S GIT-CFLAGS $(missing_dep_dirs)
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$(QUIET_CC)$(CC) -o $*.o -c $(dep_args) $(ALL_CFLAGS) $<
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ifdef COMPUTE_HEADER_DEPENDENCIES
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# Take advantage of gcc's on-the-fly dependency generation
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# See <http://gcc.gnu.org/gcc-3.0/features.html>.
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dep_files := $(wildcard $(foreach f,$(OBJECTS),$(dir f)deps/$(notdir $f).d))
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ifneq ($(dep_files),)
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include $(dep_files)
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endif
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dep_file = $(dir $@)deps/$(notdir $@).d
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dep_args = -MF $(dep_file) -MMD -MP
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else
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dep_args =
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# Dependencies on header files, for platforms that do not support
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# the gcc -MMD option.
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#
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# Dependencies on automatically generated headers such as common-cmds.h
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# should _not_ be included here, since they are necessary even when
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# building an object for the first time.
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#
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# XXX. Please check occasionally that these include all dependencies
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# gcc detects!
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$(GIT_OBJS): $(LIB_H)
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builtin-branch.o builtin-checkout.o builtin-clone.o builtin-reset.o branch.o transport.o: branch.h
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@ -1700,10 +1738,10 @@ builtin-pack-objects.o: thread-utils.h
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http-fetch.o http-walker.o remote-curl.o transport.o walker.o: walker.h
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http.o http-walker.o http-push.o remote-curl.o: http.h
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xdiff-interface.o $(XDIFF_OBJS): \
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xdiff/xinclude.h xdiff/xmacros.h xdiff/xdiff.h xdiff/xtypes.h \
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xdiff/xutils.h xdiff/xprepare.h xdiff/xdiffi.h xdiff/xemit.h
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endif
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exec_cmd.s exec_cmd.o: ALL_CFLAGS += \
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'-DGIT_EXEC_PATH="$(gitexecdir_SQ)"' \
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@ -2011,6 +2049,7 @@ clean:
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$(RM) $(ALL_PROGRAMS) $(BUILT_INS) git$X
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$(RM) $(TEST_PROGRAMS)
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$(RM) -r bin-wrappers
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$(RM) -r $(dep_dirs)
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$(RM) *.spec *.pyc *.pyo */*.pyc */*.pyo common-cmds.h TAGS tags cscope*
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$(RM) -r autom4te.cache
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$(RM) config.log config.mak.autogen config.mak.append config.status config.cache
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