https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91879
--- Comment #8 from Stas Sergeev <stsp at users dot sourceforge.net> ---
(In reply to Andrew Pinski from comment #7)
> Have you looked into --with-build-sysroot ?
Thanks! Very helpful.
But now it has the same problem when configuring libstdc++:
---
configure:4574:
/home/stas/src/build-gcc/build/djcross-gcc-9.2.0/djcross/./gcc/x
gcc -B/home/stas/src/build-gcc/build/djcross-gcc-9.2.0/djcross/./gcc/
-B/usr/loc
al/cross/i586-pc-msdosdjgpp/bin/ -B/usr/local/cross/i586-pc-msdosdjgpp/lib/
-isy
stem /usr/local/cross/i586-pc-msdosdjgpp/include -isystem
/usr/local/cross/i586-
pc-msdosdjgpp/sys-include
--sysroot=/home/stas/src/build-gcc/ttt/usr/local/cross
-c -g -O2 conftest.c >&5
conftest.c:10:10: fatal error: stdio.h: No such file or directory
10 | #include <stdio.h>
| ^~~~~~~~~
---
As you can see, it added the correct --sysroot.
But unfortunately -isystem is still unaffected.
If I change -isystem in the command line above, then
conftest.c can be compiled.
Here's the full top-level configure invocation:
---
../gnu/gcc-9.2.0/configure --disable-plugin --enable-lto --disable-libssp --
disable-nls --enable-libquadmath-support --enable-version-specific-runtime-libs
--enable-fat --enable-libstdcxx-filesystem-ts
--with-build-sysroot=/home/stas/sr
c/build-gcc/ttt/usr/local/cross --target=i586-pc-msdosdjgpp
--prefix=/usr/local/
cross --enable-languages=c,c++
---
As you can see, I added --with-build-sysroot.
