Using compiler/codegen options not provided by Zig build system

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1

Is there a way to set codegen options not exposed by the Zig build system? Specifically, I need the -mtp=... option for AArch64 to specify the TPIDR_ELx register used for thread-local accesses. The option seems to be exposed in zig cc, but not in the Zig build system itself, i.e., I cannot attach it to a module/executable.

2

You can directly pass C/C++ compiler flags via the .flags field in the addCSourceFile method. E.g. smth like:

  lib.addCSourceFiles(.{
      .files = &.{ "src/bla.c", "src/blub.c" },
      .flags = &.{ "-fno-sanitize=undefined", "..." },
  });

…not sure about linker options though.

3

Oh, I forgot to mention I need those options for Zig codegen, not for C/C++. So addCSourceFiles won’t work for me unfortunately.

4

Hmm, then I don’t know… AFAIK the cmdline options in zig cc are basically forwarded to the integrated Clang frontend, but don’t do anything for compiling Zig code.

5

For Zig, this is part of the CPU target (specifically, the CPU feature flags tpidr_el1, tpidr_el2, tpidr_el3).

With zig build-exe, etc the option is -mcpu

With build.zig and when using b.standardTargetOptions, use -Dcpu

If you want to set a specific target within build.zig, you can do something like this:

Use zig targets to see all the possible targets/cpus/features. You can add or remove feature flags by appending +<flag> or -<flag> to the end of the cpu target (and multiple additions and removals can be chained, so e.g. -mcpu=generic+foo-bar)

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