On 9/14/2026 1:34 AM, Daniel P. Berrangé wrote: > On Sun, Sep 13, 2026 at 10:08:52PM -0700, Pierrick Bouvier wrote: >> On 9/10/26 11:14 AM, Alex Bennée wrote: >>> From: Daniel P. Berrangé <[email protected]> >>> >>> When it finds a cross compiler, tests/tcg/meson.build tries >>> building test_cc.c to validate that the compiler works. This >>> includes "stdint.h" as a witness for working C library, however, >>> that is not a good choice as it can be provided by the toolchain >>> alone: >>> >>> $ rpm -ql gcc-s390x-linux-gnu | grep /stdint.h >>> /usr/lib/gcc/s390x-linux-gnu/16/include/stdint.h >>> >>> As a result, if you install the s390x GCC cross compiler, but >>> not any C library, meson decides to use the host compiler instead >>> of the container: >>> >>> cc for aarch64-softmmu : aarch64-linux-gnu-gcc (from >>> 'debian-all-test-cross' container) >>> cc for loongarch64-softmmu : loongarch64-unknown-linux-gnu-gcc >>> (from 'debian-loongarch-cross' container) >>> cc for riscv64-softmmu : riscv64-linux-gnu-gcc (from >>> 'debian-all-test-cross' container) >>> cc for s390x-softmmu : s390x-linux-gnu-gcc >>> cc for x86_64-softmmu : x86_64-linux-gnu-gcc (from >>> 'debian-amd64-cross' container) >>> >>> Eventually this results in failure to run 'make check': >>> >>> [33/40] Generating tests/tcg/s390x-softmmu-hello with a custom command >>> FAILED: [code=1] tests/tcg/s390x-softmmu-hello.test >>> /usr/bin/s390x-linux-gnu-gcc >>> /home/berrange/src/virt/qemu/tests/tcg/multiarch/system/hello.c -o >>> tests/tcg/s390x-softmmu-hello.test -static -MMD -MF >>> tests/tcg/s390x-softmmu-hello.d -Wall -Werror -O0 -g -fno-strict-aliasing >>> -nostdlib -ffreestanding -Wa,--noexecstack -I >>> /home/berrange/src/virt/qemu/tests/tcg/s390x/system/../../minilib >>> /home/berrange/src/virt/qemu/tests/tcg/s390x/system/../../minilib/printf.c >>> -I /home/berrange/src/virt/qemu/include/hw/s390x/ipl -march=z13 >>> ../tests/tcg/s390x/system/../head64.S ../tests/tcg/s390x/system/../console.c >>> In file included from ../tests/tcg/s390x/system/../console.c:8: >>> ../tests/tcg/s390x/system/../../../../pc-bios/s390-ccw/sclp.c:11:10: fatal >>> error: string.h: No such file or directory >>> 11 | #include <string.h> >>> | ^~~~~~~~~~ >>> compilation terminated. >>> >>> Adding more include files to the test program ensures the >>> meson probe makes a better decision. >>> >>> Fixes: e5d084d622b1 (tests/tcg/meson.build: check host cross cc is working) >>> Signed-off-by: Daniel P. Berrangé <[email protected]> >>> Message-ID: <[email protected]> >>> Signed-off-by: Alex Bennée <[email protected]> >>> --- >>> tests/tcg/test_cc.c | 6 +++++- >>> 1 file changed, 5 insertions(+), 1 deletion(-) >>> >>> diff --git a/tests/tcg/test_cc.c b/tests/tcg/test_cc.c >>> index d3614a01fe6..fafee055b40 100644 >>> --- a/tests/tcg/test_cc.c >>> +++ b/tests/tcg/test_cc.c >>> @@ -1,7 +1,11 @@ >>> /* SPDX-License-Identifier: GPL-2.0-or-later */ >>> -/* Include a standard header to make sure cross compiler provides them */ >>> +/* Use some standard headers to ensure the cross compiler provides them */ >>> #include <stdint.h> >>> +#include <string.h> >>> +#include <stdbool.h> >>> +#include <stddef.h> >>> +#include <stdio.h> >>> int main(void) >>> { >> >> Ideally, we should do separate tests for system vs user tests. >> System ones are always compiled with -ffreestanding, while user ones should >> provide a C library. >> >> From this standard: >> >> https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2338r3.html >> ``` >> A freestanding C implementation is required to provide the entirety of the >> following headers: >> >> <float.h> >> <iso646.h> >> <limits.h> >> <stdalign.h> >> <stdarg.h> >> <stdbool.h> >> <stddef.h> >> <stdint.h> >> <stdnoreturn.h> >> Most of <string.h> is required (strdup, strndup, strcoll, strxfrm, and >> strerror are excluded). This includes strtok, which requires global data. >> ``` >> >> Maybe for now we can just remove stdio.h from current patch, as it's not >> supposed to be provided in a freestanding environment. > > A huge number of files under tests/tcg/ have a #include <stdio.h> > currently. > > In the example build failure in the commit message, we have > > tests/tcg/s390x/system/../console.c > > which does > > #include "../../../pc-bios/s390-ccw/sclp.c" > > and sclp.c has > > #include "s390-ccw.h" > > and that header has: > > #include <stdbool.h> > #include <stddef.h> > #include <stdint.h> > #include <stdio.h> > > hence the 4 headers I added to the meson check. > > So AFAICT, our code is expecting stdio.h to be provided in a > -ffreestanding build. Have we got a more fundamental mistake > wrt our use of -ffreestanding, such that it is relying on > unintended functionality ? >
Looking a bit further, it seems that this is the only example of system code pulling this header (through pc-bios), which might be a specificity of s390x firmware. That said, it's not the end of the world, and as we mostly use -linux-gcc variants of cross compilers, it should be safe to expect them to come with a libc. Let's keep the patch as it is. > With regards, > Daniel Thanks, Pierrick
