`checking size of mp_limb_t... 0` and `configure: error: Oops, mp_limb_t doesn't seem to work` when compiling the Microchip XC32 compiler from source

[Niels Möller]

"Gabriel Staples, ElectricRCAircraftGuy.com" <ercaguy at gmail.com> writes:

> In the answer <https://stackoverflow.com/a/77435216/4561887>, please jump
> halfway down, to the section titled "Explanation of the
> ${gcc_srcdir_RELATIVE}/configure relative path fix that works". I can
> neither explain it more nor less simply than that.

So actual error from your config.log is

  configure:27432: gcc -c -g -O2 -D__USE_MINGW_ACCESS -DNO_ASM -I/c/Users/gabriel/GS/dev/Microchip_XC32_Compiler/xc32-v4.35-src/pic32m-build/opt/include -imacros host-defs.h conftest.c >&5
  conftest.c:80:10: fatal error: /c/Users/gabriel/GS/dev/Microchip_XC32_Compiler/xc32-v4.35-src/pic32m-source/gcc/gmp/gmp-h.in: No such file or directory
     80 | #include "/c/Users/gabriel/GS/dev/Microchip_XC32_Compiler/xc32-v4.35-src/pic32m-source/gcc/gmp/gmp-h.in"
        |
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  compilation terminated.

And that is from running gmp's configure script, not the configure
script of one of the other components your building? That looks rather
strange to me:

(1) I'm not used to autoconf putting absolute file names in #include
    lines in conftest.c. At least, I have never noticed it doing that.

(2) It makes no sense for any C code, in conftest.c or otherwise, to
    ever attempt to include gmp-h.in. That's not a valid C header file,
    since it lacks the substitutions that turns it into a valid gmp.h
    header file.

Regards,
/Niels

-- 
Niels Möller. PGP key CB4962D070D77D7FCB8BA36271D8F1FF368C6677.
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