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ziglang / zig

General-purpose programming language and toolchain for maintaining robust, optimal, and reusable software.
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Unused shared library is not linked in executable #22011

Closed Mnohem closed 3 days ago

Mnohem commented 4 days ago

Zig Version

0.14.0-dev.2252+7266d4497

Steps to Reproduce and Observed Behavior

❯ uname -a
Linux frame.void 6.11.6_1 #1 SMP PREEMPT_DYNAMIC Sun Nov  3 20:15:56 UTC 2024 x86_64 GNU/Linux
  1. Link a shared library to your executable in build.zig
  2. Do not use that library or anything depending on that library in your executable
  3. The resulting binary will not have a link to said shared library

This causes issues with loading dynamic libraries at runtime if those libraries depend on the shared library that should be linked, as this causes the shared library to be loaded/reloaded along with the dynlib at runtime.

Expected Behavior

Link all shared libraries as outlined in build.zig, regardless of usage. This was the previous behavior, but some change since dev.1800 seemed to have caused this regression.

xdBronch commented 4 days ago

this isnt a zig specific bug, the same will happen in e.g. C, its just something linkers do afaik. on the cli you can use -needed-l in place of -l and in build.zig you can use exe.linkSystemLibrary2("name", .{ .needed = true })

Mnohem commented 3 days ago

I see, I assumed it was a bug since the change affected my project negatively, my bad. However I can't seem to find a way in the build system to add this flag for non-system libraries? linkLibrary takes no options and there is no linkLibrary2.

xdBronch commented 3 days ago

hmm, that i dont have a solution for. zig handles those libraries a little differently, rather than passing -lfoo it passes the full path to the library file itself then adds the containing directory as an rpath. im not sure if the CLI provides a way to declare those as needed

Mnohem commented 3 days ago

Interesting, well luckily the workaround is simple, just have to use the library at runtime and it gets linked properly.