On Tue, May 6, 2025 at 5:47 AM Junio C Hamano <gitster@xxxxxxxxx> wrote: > > Torsten Bögershausen <tboegi@xxxxxx> writes: > > > There is a problem with the somewhat new > > commit 82e79c63642c introducing NOT_CONSTANT with sigfillset(): > > > > Compiling on older (?) MacOs machine leads to this: > > Undefined symbols for architecture x86_64: > > "_false_but_the_compiler_does_not_know_it_", referenced from: > > _start_command in libgit.a(run-command.o) > > > > What is the best thing to avoid this ? > > > > The introduced "false_but_the_compiler_does_not_know_it" triggers here > > because there is a proper prototype in signal.h and then a > > #define sigfillset() ... > > further down in the file, which can never fail. > > > > a) Define a sigfillset_or_die_if_needed macro, > > which does what we have today, and is simply defined > > as sigfillset() without any error checking for MacOs(some version) > > b) Revert the commit (and fix the conflicts) > > c) Anything better ? > > > > I have a raw patch for b), not fully cooked, as the commit message > > is the hardest part. Before sending that out: > > Are the thoughts about a better solution ? > > How about figuring out why it does not work on your system? > > Namely, compiling compiler-tricks/not-constant.c should yield > compiler-tricks/not-constant.o and that should be "ar"ed into > libgit.a, just like config.o, connect.o, etc., so I cannot see how > your ld fails to find false_but_the_compiler_does_not_know_it when > it has no problem with say git_config or other global symbols. > I reproduced the issue with Xcode 14.2 on macOS Monterey. It seems to be caused by the ld command's bug and can be avoided by tweaking Makefile: diff --git a/Makefile b/Makefile index 8a7f1c7654..8a06db8400 100644 --- a/Makefile +++ b/Makefile @@ -1387,7 +1387,7 @@ UNIT_TEST_OBJS += $(UNIT_TEST_DIR)/test-lib.o UNIT_TEST_OBJS += $(UNIT_TEST_DIR)/lib-reftable.o # xdiff and reftable libs may in turn depend on what is in libgit.a -GITLIBS = common-main.o $(LIB_FILE) $(XDIFF_LIB) $(REFTABLE_LIB) $(LIB_FILE) +GITLIBS = common-main.o $(LIB_FILE) $(XDIFF_LIB) $(REFTABLE_LIB) $(LIB_FILE) compiler-tricks/not-constant.o EXTLIBS = GIT_USER_AGENT = git/$(GIT_VERSION) or by explicitly initializing false_but_the_compiler_does_not_know_it_ (which changes the symbol type from 'C' to 'S'): diff --git a/compiler-tricks/not-constant.c b/compiler-tricks/not-constant.c index 1da3ffc2f5..9fb4f275b1 100644 --- a/compiler-tricks/not-constant.c +++ b/compiler-tricks/not-constant.c @@ -1,2 +1,2 @@ #include <git-compat-util.h> -int false_but_the_compiler_does_not_know_it_; +int false_but_the_compiler_does_not_know_it_ = 0; Koji Nakamaru
