Portability means we cannot completely switch over to
automatically generated dependencies on header files, since some
compilers do not support them. This would seem to lead to a
dangerous situation in which the hand-written dependency rules
are needed for some configurations but poorly maintained because
most configurations do not use them.
Luckily, there is a way out: as part of testing git, ask the
build system to verify that the hand-written dependency rules are
consistent with the automatically generated ones. This patch is
a start towards that goal.
The actual patch requires a few steps:
1. Separate out a USE_COMPUTED_HEADER_DEPENDENCIES option to
tell make to use the makefile snippets stored in deps/*
without necessarily regenerating them;
2. Add a PRINT_HEADER_DEPENDENCIES option to turn on
USE_COMPUTED_HEADER_DEPENDENCIES and make the %.o: %.c rule
print its prerequisites instead of compiling anything;
3. Add a CHECK_HEADER_DEPENDENCIES option to turn off
USE_COMPUTED_HEADER_DEPENDENCIES and make the %.o: %.c rule
check that its prerequisites includes all files listed by
'make -s PRINT_HEADER_DEPENDENCIES=YesPlease $@' instead of
compiling anything.
With this patch applied,
echo COMPUTE_HEADER_DEPENDENCIES=YesPlease >> config.mak
make clean
make
make CHECK_HEADER_DEPENDENCIES=YesPlease
produces a useful error message:
CHECK fast-import.o
missing dependencies: exec_cmd.h
make: *** [fast-import.o] Error 1
Probably we should check for missing deps/%.o.d files to avoid
false negatives if some are missing.
Signed-off-by: Jonathan Nieder <jrnieder@xxxxxxxxx>
---
I look forward to your thoughts.
This is a bit clunky, but it is useful enough to detect a few problems
with the current dependency rules. Patches should follow soon.
Makefile | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++------
1 files changed, 67 insertions(+), 7 deletions(-)
diff --git a/Makefile b/Makefile
index 578843c..e642a24 100644
--- a/Makefile
+++ b/Makefile
@@ -224,6 +224,8 @@ all::
#
# Define COMPUTE_HEADER_DEPENDENCIES if you want to avoid rebuilding objects
# when an unrelated header file changes and your compiler supports it.
+#
+# Define CHECK_HEADER_DEPENDENCIES after a successful build to find problems.
GIT-VERSION-FILE: FORCE
@$(SHELL_PATH) ./GIT-VERSION-GEN
@@ -1064,6 +1066,28 @@ endif
-include config.mak.autogen
-include config.mak
+ifdef PRINT_HEADER_DEPENDENCIES
+CHECK_HEADER_DEPENDENCIES = YesPlease
+endif
+
+ifdef CHECK_HEADER_DEPENDENCIES
+ifndef COMPUTE_HEADER_DEPENDENCIES
+$(error checking dependencies requires build with COMPUTE_HEADER_DEPENDENCIES)
+endif
+endif
+
+ifdef COMPUTE_HEADER_DEPENDENCIES
+ifdef CHECK_HEADER_DEPENDENCIES
+ifdef PRINT_HEADER_DEPENDENCIES
+USE_COMPUTED_HEADER_DEPENDENCIES = YesPlease
+else
+USE_COMPUTED_HEADER_DEPENDENCIES =
+endif
+else
+USE_COMPUTED_HEADER_DEPENDENCIES = YesPlease
+endif
+endif
+
ifdef SANE_TOOL_PATH
SANE_TOOL_PATH_SQ = $(subst ','\'',$(SANE_TOOL_PATH))
BROKEN_PATH_FIX = 's|^\# @@BROKEN_PATH_FIX@@$$|git_broken_path_fix $(SANE_TOOL_PATH_SQ)|'
@@ -1669,14 +1693,48 @@ endif
.SUFFIXES:
+ifdef CHECK_HEADER_DEPENDENCIES
+
+ifdef PRINT_HEADER_DEPENDENCIES
+$(C_OBJ): %.o: %.c FORCE
+ echo $^
+$(ASM_OBJ): %.o: %.S FORCE
+ echo $^
+else
+missing_deps = $(filter-out $^, \
+ $(shell $(MAKE) -s PRINT_HEADER_DEPENDENCIES=1 $@))
+
+$(C_OBJ): %.o: %.c FORCE
+ @set -e; echo CHECK $@; \
+ missing_deps="$(missing_deps)"; \
+ if test "$$missing_deps"; \
+ then \
+ echo missing dependencies: $$missing_deps; \
+ false; \
+ fi
+$(ASM_OBJ): %.o: %.S FORCE
+ @set -e; echo CHECK $@; \
+ missing_deps="$(missing_deps)"; \
+ if test "$$missing_deps"; \
+ then \
+ echo missing dependencies: $$missing_deps; \
+ false; \
+ fi
+endif
+
+else
+
$(C_OBJ): %.o: %.c GIT-CFLAGS $(dep_dir_dep)
$(QUIET_CC)$(CC) -o $*.o -c $(dep_args) $(ALL_CFLAGS) $<
-%.s: %.c GIT-CFLAGS FORCE
- $(QUIET_CC)$(CC) -S $(ALL_CFLAGS) $<
$(ASM_OBJ): %.o: %.S GIT-CFLAGS $(dep_dir_dep)
$(QUIET_CC)$(CC) -o $*.o -c $(dep_args) $(ALL_CFLAGS) $<
-ifdef COMPUTE_HEADER_DEPENDENCIES
+endif
+
+%.s: %.c GIT-CFLAGS FORCE
+ $(QUIET_CC)$(CC) -S $(ALL_CFLAGS) $<
+
+ifdef USE_COMPUTED_HEADER_DEPENDENCIES
# Take advantage of gcc's dependency generation
# See <http://gcc.gnu.org/gcc-3.0/features.html>.
dep_files := $(wildcard $(foreach f,$(OBJECTS),$(dir f)deps/$(notdir $f).d))
@@ -1684,9 +1742,6 @@ dep_files := $(wildcard $(foreach f,$(OBJECTS),$(dir f)deps/$(notdir $f).d))
ifneq ($(dep_files),)
include $(dep_files)
endif
-
-dep_file = $(dir $@)deps/$(notdir $@).d
-dep_args = -MF $(dep_file) -MMD -MP
else
$(GIT_OBJS): $(LIB_H)
http.o http-walker.o http-push.o: http.h
@@ -1695,7 +1750,12 @@ builtin-revert.o wt-status.o: wt-status.h
$(XDIFF_OBJS): xdiff/xinclude.h xdiff/xmacros.h xdiff/xdiff.h xdiff/xtypes.h \
xdiff/xutils.h xdiff/xprepare.h xdiff/xdiffi.h xdiff/xemit.h
+endif
+ifdef COMPUTE_HEADER_DEPENDENCIES
+dep_file = $(dir $@)deps/$(notdir $@).d
+dep_args = -MF $(dep_file) -MMD -MP
+else
dep_args =
endif
@@ -1823,7 +1883,7 @@ test-delta$X: diff-delta.o patch-delta.o
test-parse-options$X: parse-options.o
-ifndef COMPUTE_HEADER_DEPENDENCIES
+ifndef USE_COMPUTED_HEADER_DEPENDENCIES
test-parse-options.o: parse-options.h
endif
--
1.6.6.rc2
--
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