Am 11. Juli 2025 10:45:08 UTC schrieb Peter Maydell <peter.mayd...@linaro.org>:
>On Tue, 17 Jun 2025 at 21:35, Bernhard Beschow <shen...@gmail.com> wrote:
>>
>> When compiling QEMU against fuse3-3.17.1 with --enable-werror the build fails
>> with:
>>
>> In file included from ../src/block/export/fuse.c:33:
>> /usr/include/fuse3/fuse.h:959:5: error: redundant redeclaration of
>> ‘fuse_main_real_versioned’ [-Werror=redundant-decls]
>> 959 | int fuse_main_real_versioned(int argc, char *argv[],
>> | ^~~~~~~~~~~~~~~~~~~~~~~~
>> /usr/include/fuse3/fuse.h:885:5: note: previous declaration of
>> ‘fuse_main_real_versioned’ with type ‘int(int, char **, const struct
>> fuse_operations *, size_t, struct libfuse_version *, void *)’ {aka
>> ‘int(int, char **, const struct fuse_operations *, long unsigned int,
>> struct libfuse_version *, void *)’}
>> 885 | int fuse_main_real_versioned(int argc, char *argv[],
>> | ^~~~~~~~~~~~~~~~~~~~~~~~
>> cc1: all warnings being treated as errors
>>
>> That is, a fuse header triggers a warning within itself. Since QEMU adds the
>> fuse3 include path via `-I`, the compiler thinks that the header is part of
>> the
>> QEMU project, and thus raises a warning. The compiler can be told to ignore
>> warnings within 3rd party headers by adding these paths via `-isystem`. Fix
>> the
>> above build failure by marking fuse as system dependency. While at it mark
>> every 3rd-party dependency as system dependency to prevent similar issues in
>> the
>> future but skip glib since that results in glib include paths to be omitted
>> from
>> bindgen in case of a Rust build.
>
>The problem with this is that -isystem does not only do "suppress
>warnings in these headers" -- it also alters the search order
>for includes, in a way that can sometimes cause problems:
>https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70129
>So this isn't completely risk-free, though I think meson tries to
>avoid some of this by doing something a bit more complex than a
>pure 's/-I/-isystem/'.
>
>We would also lose the warnings about e.g. use of deprecated
>functions in our dependencies.
AFAIU the include_type parameter only affects how QEMU itself is built but
doesn't affect Meson subprojects. Therefore, we should still see deprecation
warnings from dependencies in our own code.
Best regards,
Bernhard
>
>All that said, this might still be the best tradeoff.
>
>thanks
>-- PMM
