Hi!

Ludovic Courtès <ludo@gnu.org> skribis:

> /tmp/guix-build-gcc-10.1.0.drv-0/build/prev-x86_64-unknown-linux-gnu/libstdc++-v3/config.log
> reads this:
>
> configure:19924: checking for float trig functions
> configure:19948:  /tmp/guix-build-gcc-10.1.0.drv-0/build/./gcc/xgcc -shared-libgcc -B/tmp/guix-build-gcc-10.1.0.drv-0/build/./gcc -nostdinc++ -L/tmp/guix-build-gcc-10.1.0.drv-0/build/x86_64-unknown-linux-gnu/libstdc++-v3/src -L/tmp/guix-build-gcc-10.1.0.drv-0/build/x86_64-unknown-linux-gnu/libstdc++-v3/src/.libs -L/tmp/guix-build-gcc-10.1.0.drv-0/build/x86_64-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs -B/gnu/store/jrzxs91zhpf6yr5fxisn3jjj7xai8zlk-gcc-10.1.0/x86_64-unknown-linux-gnu/bin/ -B/gnu/store/jrzxs91zhpf6yr5fxisn3jjj7xai8zlk-gcc-10.1.0/x86_64-unknown-linux-gnu/lib/ -isystem /gnu/store/jrzxs91zhpf6yr5fxisn3jjj7xai8zlk-gcc-10.1.0/x86_64-unknown-linux-gnu/include -isystem /gnu/store/jrzxs91zhpf6yr5fxisn3jjj7xai8zlk-gcc-10.1.0/x86_64-unknown-linux-gnu/sys-include   -fno-checking -c -fno-builtin -D_GNU_SOURCE  conftest.cpp >&5
> In file included from /gnu/store/rn75fm7adgx3pw5j8pg3bczfqq1y17lk-gcc-7.5.0/include/c++/math.h:36,
>                  from conftest.cpp:122:
> /gnu/store/rn75fm7adgx3pw5j8pg3bczfqq1y17lk-gcc-7.5.0/include/c++/cmath:41:10: fatal error: bits/c++config.h: No such file or directory
>    41 | #include <bits/c++config.h>
>       |          ^~~~~~~~~~~~~~~~~~
> compilation terminated.
> configure:19948: $? = 1
> configure: failed program was:
>
> [...]
>
> | /* end confdefs.h.  */
> | #include <math.h>
> | int
> | main ()
> | {
> | acosf (0); asinf (0); atanf (0); cosf (0); sinf (0); tanf (0); coshf (0); sinhf (0); tanhf (0);
> |   ;
> |   return 0;
> | }
> configure:19962: result: no

The attached patch addresses this with a questionable yet efficient
hack.  The test cases reported by Maxim and by Erik Garrison now build
fine.

I’ve asked for guidance for a proper fix at
<https://gcc.gnu.org/pipermail/gcc-help/2020-July/139204.html>, but in
the meantime, I’m happy to go with this patch.

Thoughts?

Thanks,
Ludo’.