[PATCH] Makefile: drop duplicate %.a from link recipes

[PATCH] Makefile: drop duplicate %.a from link recipes

[Harald Nordgren via GitGitGadget]

From: Harald Nordgren <haraldnordgren@gmail.com>

Three link recipes list archive files twice on the link line: once
via $(filter %.a,$^) and again through $(LIBS), which expands to
$(filter-out %.o,$(GITLIBS)) $(EXTLIBS). On macOS the linker warns
about the duplicates:

  ld: warning: ignoring duplicate libraries: 'libgit.a', 'target/release/libgitcore.a'

Drop the redundant filter from the test-helper, fuzz-program, and
unit-test recipes so they match the pattern used by other link
recipes in the file.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
    Makefile: drop duplicate %.a from test-helper link rule

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2314%2FHaraldNordgren%2Fmakefile-test-helper-dedup-libs-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2314/HaraldNordgren/makefile-test-helper-dedup-libs-v1
Pull-Request: https://github.com/git/git/pull/2314

 Makefile | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index b31ecb0756..309d1d1e74 100644
--- a/Makefile
+++ b/Makefile
@@ -3392,7 +3392,7 @@ perf: all
 t/helper/test-tool$X: $(patsubst %,t/helper/%,$(TEST_BUILTINS_OBJS)) $(UNIT_TEST_DIR)/test-lib.o
 
 t/helper/test-%$X: t/helper/test-%.o GIT-LDFLAGS $(GITLIBS)
-	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) $(filter %.a,$^) $(LIBS)
+	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) $(LIBS)
 
 check-sha1:: t/helper/test-tool$X
 	t/helper/test-sha1.sh
@@ -4015,13 +4015,13 @@ fuzz-all: $(FUZZ_PROGRAMS)
 $(FUZZ_PROGRAMS): %: %.o oss-fuzz/dummy-cmd-main.o $(GITLIBS) GIT-LDFLAGS
 	$(QUIET_LINK)$(FUZZ_CXX) $(FUZZ_CXXFLAGS) -o $@ $(ALL_LDFLAGS) \
 		-Wl,--allow-multiple-definition \
-		$(filter %.o,$^) $(filter %.a,$^) $(LIBS) $(LIB_FUZZING_ENGINE)
+		$(filter %.o,$^) $(LIBS) $(LIB_FUZZING_ENGINE)
 
 $(UNIT_TEST_PROGS): $(UNIT_TEST_BIN)/%$X: $(UNIT_TEST_DIR)/%.o $(UNIT_TEST_OBJS) \
 	$(GITLIBS) GIT-LDFLAGS
 	$(call mkdir_p_parent_template)
 	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) \
-		$(filter %.o,$^) $(filter %.a,$^) $(LIBS)
+		$(filter %.o,$^) $(LIBS)
 
 GIT-TEST-SUITES: FORCE
 	@FLAGS='$(CLAR_TEST_SUITES)'; \

base-commit: 1666c1265231b0bc5f613fbbf3f0a9896cdef76e
-- 
gitgitgadget

Re: [PATCH] Makefile: drop duplicate %.a from link recipes

[Junio C Hamano]

"Harald Nordgren via GitGitGadget" <gitgitgadget@gmail.com> writes:

>  t/helper/test-%$X: t/helper/test-%.o GIT-LDFLAGS $(GITLIBS)
> -	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) $(filter %.a,$^) $(LIBS)
> +	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) $(LIBS)

I think the reason why the pattern to use only the .o files among
the prerequisites and then use only the .a files among the same
prerequisites (both filters $^) is used here is to make sure that the
linker sees object files first before library archives, so that by
the time its left-to-right scan sees the first library archive, all
the missing symbols in the object files are known.  The above change
depends on LIBS being a strict superset of all the library archive
files ($GITLIBS in the current code, but that can be updated in the
future) listed as prerequisites for the rule, but there is nothing to
guarantee that, so it looks brittle.

Exact same comment applies to the other two rules touched by this patch.