On Tue, 11 Jun 2024 at 07:31, Eli Zaretskii <e...@gnu.org> wrote: > > > From: Richard Copley <rcop...@gmail.com> > > Date: Mon, 10 Jun 2024 23:29:28 +0100 > > Cc: help-make@gnu.org > > > > Having passed that hurdle, I see that GCC does not handle the > > named-semaphore jobserver in native GNU Make on Windows. (I had to > > read GCC's source to see it, since the error in that case simply says > > "'--jobserver-auth=' is not present in MAKEFLAGS". This subproblem > > appears to be unintentional and I have reported it on the GCC > > bugtracker.) None of that is a Make problem, of course. > > Just curious: why does GCC need to know about Make's jobserver? > (Since you say "GCC source", I presume you are not talking about the > GCC build scripts, but GCC itself.)
Its link-time optimization has some jobs to perform in parallel, and attempts to do so by writing out a makefile and executing the program named in the environment variable "MAKE" (or by executing "make", if none). At the linking stage, when using link-time optimization, one often gets the following message: lto-wrapper.exe: warning: using serial compilation of 2 LTRANS jobs lto-wrapper.exe: note: see the '-flto' option documentation for more information The "-flto" documentation does not directly explain the error or what to do about it, so one has a fun puzzle. (Or one can ignore the warning, as I have been doing for many years already. It doesn't do any harm.) Passing "-flto=jobserver" does not work, in the first instance because the "--jobserver-auth=" argument in MAKEARGS is overvalidated. GCC ignores it (and removes it from MAKEARGS) unless it is a pair of numbers or contains "fifo:". But passing "-flto=n" (where n is a number which should be used as the argument to the "-j" option in the inferior make) does not work either. One can set "export MAKE:=$(MAKE)" in a target-specific variable in the top-level makefile to pass "mingw32-make" (the installed name of native Windows GNU Make in its MSYS2 package) through to GCC, and then GCC creates a temporary makefile and executes "mingw32-make", but an error message is printed: The system cannot find the path specified. mingw32-make[1]: [C:\Users\buster\AppData\Local\Temp\cc4moXuq.mk:3: C:\Users\buster\AppData\Local\Temp\ccCEYc1I.ltrans0.ltrans.o] Error 1 (ignored) The file that could not be found is presumably "$(prefix)/lib/gcc/x86_64-w64-mingw32/14.1.0/collect2.exe" (another layer of wrapping for the linker). I don't know why it isn't found. Perhaps it is not on the path. By this time the temporary makefile has been deleted, and for now, I have lost the motivation to debug further.
