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thom311 / libnl

Netlink Library Suite
GNU Lesser General Public License v2.1
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Unused symbol versioning #375

Closed lch361 closed 4 months ago

lch361 commented 4 months ago

I have detected this problem while I was using different linkers for this project.

In this version script file libnl-3.sym, a symbol nl_debug_dp is defined. However, when doing ./configure --disable-debug, there is no nl_debug_dp variable around, so a symbol is undefined. If the linker is configured to deny unused versions, this is a build error. Building with ld.bfd usually succeeds, because its option --undefined-version is set by default, while building with ld.lld fails because its --undefined-version isn't set by default.

This patch fixes this, enabling --undefined-version flag for every linker for every build.

thom311 commented 4 months ago

thanks for the report and the patch.

But I think this is the wrong solution.

The linker error about bugs in the .sym files is very useful. The unit tests in github actions also enable that linker flag (regardless whether it's the default). Granted, they didn't catch the problem because they didn't build with --enable-debug=no. That is fixed now by commit 13ab0122fc38462d16b2aa920167220ca196f15d.

I guess, if the ABI heavily depends on configure options, then disabling the linker check may make some sense. But libnl doesn't do that (except for nl_debug_dp), and it's probably a bad idea anyway.

This should be solved now with merge commit 96ddcd999297d8697235e75417bda8a66e26bb0f.