* Richard Biener: > On Fri, Dec 1, 2023 at 9:04 AM Florian Weimer via Gcc <gcc@gcc.gnu.org> wrote: >> >> I've received a report of a mingw build failure: >> >> ../../../gcc/libgcc/libgcov-interface.c: In function '__gcov_fork': >> ../../../gcc/libgcc/libgcov-interface.c:185:9: error: implicit declaration >> of function 'fork' [-Wimplicit-function-declaration] >> 185 | pid = fork (); >> | ^~~~ >> make[2]: *** [Makefile:932: _gcov_fork.o] Error 1 >> make[2]: *** Waiting for unfinished jobs.... >> >> As far as I understand it, mingw doesn't have fork and doesn't declare >> it in <unistd.h>, so it's not clear to me how this has ever worked. I >> would expect a linker failure. Maybe that doesn't happen because the >> object containing a reference to fork is only ever pulled in if the >> application calls the intercepted fork, which doesn't happen on mingw. >> >> What's the best way to fix this? I expect it's going to impact other >> targets (perhaps for different functions) because all of >> libgcov-interface.c is built unconditionally. I don't think we run >> configure for the target, so we can't simply check for a definition of >> the HAVE_FORK macro. > > This is wrapped inside > > #ifdef L_gcov_fork > #endif > > grepping didn't find me what defines this, but it suggests the solution > lies there ...
That's just the general libgcc/ coding style, which puts multiple related functions into one C source file. The file is compiled multiple times with different -D options using Makefile rules like this one: $(libgcov-interface-objects): %$(objext): $(srcdir)/libgcov-interface.c $(srcdir)/gcov.h $(srcdir)/libgcov.h $(gcc_compile) -DL$* -c $(srcdir)/libgcov-interface.c It looks like this is done to emulate -Wl,--gc-sections without separate source files. Unfortunately, this is all built unconditionally. Thanks, Florian