Hi, Sergei Trofimovich via Gcc <gcc@gcc.gnu.org> writes:
> Sounds good. Do you have any preference over specific syntax? My > suggestions would be: > > 1. `-fmacro-prefix-map=file-name`: if `file-name` there is not in `key=val` > format then treat it as file > 2. `-fmacro-prefix-map=@file-name`: use @ as a signal to use file > 3. `fmacro-prefix-map-file=file-name`: use a new option > >> Btw, I thought we have response files to deal with command-line limits, >> why doesn't that work here? I see the driver expands response files >> but IIRC it also builds those when the command-line gets too large >> and uses it for the environment and the cc1 invocation? If it doesn't >> do the latter why not fix it that way? > > Yeah, in theory response files would extend the limit. In practice `gcc` > always extends response files internally into a single > `COLLECT_GCC_OPTIONS` option and hits the environment variable limit > very early: > > https://gcc.gnu.org/PR111527 Doesn't it make more sense to fix this? The issue is more general than just this option (even if manifesting like so today). Can the COLLECT_GCC_OPTIONS consumers deal with argfiles? > Example reproducer: > > $ for i in `seq 1 1000`; do printf -- "-fmacro-prefix-map=%0*d=%0*d\n" > 200 1 200 2; done > a.rsp > $ touch a.c; gcc @a.rsp -c a.c > gcc: fatal error: cannot execute 'cc1': execv: Argument list too long > compilation terminated. > > And if you want to look at the gory details: > > $ strace -f -etrace=execve -s 1000000 -v -v -v gcc @a.rsp -c a.c > ... > [pid 78] execve("cc1", ["cc1", "-quiet", "a.c", "-quiet", "-dumpbase", > "a.c", "-dumpbase-ext", ".c", "-mtune=generic", "-march=x86-64", > "-fmacro-prefix-map=...=...", > "-fmacro-prefix-map=...=...", > ...], > [..., > "COLLECT_GCC=gcc", > "COLLECT_GCC_OPTIONS='-fmacro-prefix-map=...=...' > '-fmacro-prefix-map=...=...' ... '-c' '-mtune=generic' '-march=x86-64'"]) = > -1 E2BIG (Argument list too long) > > Note how `gcc` not only expands response file into an argument list > (that is not too bad) but also duplicates the whole list as a single > `COLLECT_GCC_OPTIONS=...` environment variable with added quoting on > top. > > Would be nice if `gcc` just passed response files around as is :) -- Arsen Arsenović
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