Hello Janneke, Attached a patch to relax gcc-14 for rumpkernel for core-packages-team. It might be not be needed with the 20250111 tag but I have not found the patience to look into updating it. It overwrites HOST_CFLAGS which are -O by default. Let me know if you want to add the -Wno-implicit-function-declaration instead of replacing. May 6, 2025, 15:23 by yelninei@tutamail.com: > Hi Janneke, > > May 6, 2025, 13:16 by janneke@gnu.org: > >> >> Hmm, any idea why adding that flag has become necessary? Should that >> maybe be part of this patch set then? If so, you can send a "fixup!" or >> "squash!" commit. >> > The -Wno-implicit-function-declaration is for rumpkernel and unrelated to hurd/mach. > I have just started trying to send some of the patches I have been sitting on for a while. > > Here is the full error: > /tmp/guix-build-rumpkernel-0-20211031-0.f1ffd64.drv-0/source/> buildrump.sh/src/tools/sed/../../usr.bin/sed/process.c > : In function 'lputs': > /tmp/guix-build-rumpkernel-0-20211031-0.f1ffd64.drv-0/source/> buildrump.sh/src/tools/sed/../../usr.bin/sed/process.c:636:41 > : error: implicit declaration of function 'wcwidth' [-Wimplicit-function-declaration] >   636 |                         width = (size_t)wcwidth(wc); > > > This is caused by using gcc-14 for the HOST_CC and adding gcc-14 as a native-input reproduces the issue on the master branch. Until now the HOST_CC was gcc-11 and only the CROSS_CC has been gcc-14. > > In my current checkout I have "fixed" it by adding >  -V HOST_CFLAGS=-Wno-implicit-function-declaration to the build.sh invocation to silence the warning. > > I also saw that rumpkernel has a 20250111 tag in the debian repository but struggled adapting the build system to the new version. > > >