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ca6edbd9c8
The nil Rust test fails to link when built under Coverity (cov-build):
/usr/bin/ld: src/util/libmesa_util.a.p/format_u_format_other.c.o:
undefined reference to symbol 'sqrtf@@GLIBC_2.2.5'
/usr/bin/ld: /lib/x86_64-linux-gnu/libm.so.6:
error adding symbols: DSO missing from command line
This does not reproduce with plain GCC or Clang builds.
When rustc invokes the linker for the nil test binary, the generated
link command is structured as:
cc ... [Rust rlibs] -Bdynamic -lm -ldl -lc ...
-fuse-ld=lld -B.../gcc-ld ...
[static archives: libmesa_util.a ...]
The -lm appears before libmesa_util.a in both Coverity and non-Coverity
builds. With --as-needed enabled, the linker only records a shared
library as needed if it resolves an undefined symbol at the point it
is encountered. Since no symbols need -lm when it is first seen, the
outcome depends on the linker implementation:
- lld (rustc's bundled linker, used in plain builds): Tolerates
back-references from later static archives to earlier shared
libraries, so libmesa_util.a's sqrtf reference is still resolved
by the previously-seen libm.so.
- ld.bfd (GNU ld): Strict single-pass left-to-right. Once -lm is
skipped by --as-needed, it cannot satisfy sqrtf when libmesa_util.a
is processed later.
Coverity's cov-build wrapper intercepts rustc's call to the linker
and strips the -fuse-ld=lld and -B.../gcc-ld arguments, causing the
linker to fall back to the system's ld.bfd. This exposes the latent
link-order problem that lld was masking.
The underlying issue is that rustc places default libraries (-lm, -lc,
etc.) before user-specified static archives in the link command, which
is a known rustc limitation.
See also: https://github.com/rust-lang/rust/issues/154975
Fix this by passing -lm via rust_args with --no-as-needed brackets.
This forces ld.bfd to record libm as needed regardless of when it
appears on the command line, so sqrtf from libmesa_util.a is resolved
correctly under both lld and ld.bfd.
Fixes:
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|---|---|---|
| .ci-farms | ||
| .ci-farms-disabled | ||
| .github/workflows | ||
| .gitlab | ||
| .gitlab-ci | ||
| .marge/hooks | ||
| android | ||
| bin | ||
| build-support | ||
| docs | ||
| include | ||
| licenses | ||
| src | ||
| subprojects | ||
| .clang-format | ||
| .clang-format-ignore | ||
| .clang-format-include | ||
| .dir-locals.el | ||
| .editorconfig | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
| .gitignore | ||
| .gitlab-ci.yml | ||
| .graphqlrc.yml | ||
| .mailmap | ||
| .mr-label-maker.yml | ||
| .shellcheckrc | ||
| clippy.toml | ||
| CODEOWNERS | ||
| meson.build | ||
| meson.options | ||
| README.rst | ||
| rustfmt.toml | ||
| VERSION | ||
`Mesa <https://mesa3d.org>`_ - The 3D Graphics Library ====================================================== Source ------ This repository lives at https://gitlab.freedesktop.org/mesa/mesa. Other repositories are likely forks, and code found there is not supported. Build & install --------------- You can find more information in our documentation (`docs/install.rst <https://docs.mesa3d.org/install.html>`_), but the recommended way is to use Meson (`docs/meson.rst <https://docs.mesa3d.org/meson.html>`_): .. code-block:: sh $ meson setup build $ ninja -C build/ $ sudo ninja -C build/ install Support ------- Many Mesa devs hang on IRC; if you're not sure which channel is appropriate, you should ask your question on `OFTC's #dri-devel <irc://irc.oftc.net/dri-devel>`_, someone will redirect you if necessary. Remember that not everyone is in the same timezone as you, so it might take a while before someone qualified sees your question. To figure out who you're talking to, or which nick to ping for your question, check out `Who's Who on IRC <https://dri.freedesktop.org/wiki/WhosWho/>`_. The next best option is to ask your question in an email to the mailing lists: `mesa-dev\@lists.freedesktop.org <https://lists.freedesktop.org/mailman/listinfo/mesa-dev>`_ Bug reports ----------- If you think something isn't working properly, please file a bug report (`docs/bugs.rst <https://docs.mesa3d.org/bugs.html>`_). Contributing ------------ Contributions are welcome, and step-by-step instructions can be found in our documentation (`docs/submittingpatches.rst <https://docs.mesa3d.org/submittingpatches.html>`_). Note that Mesa uses gitlab for patches submission, review and discussions.