zig cc silently ignores `-fuse-ld=` option

[jiridanek]

Zig Version

0.11.0

Steps to Reproduce and Observed Behavior

This is a follow-up to

• zig cc: unsupported darwin linker args #4841 (comment)
• linker identification issues when using zig as C compiler for meson based projects #17480 (comment)

First issue wants to simply opt out from zig cc for linking to workaround a missing linker argument (and that is also my original desire, my issue is #18356)

The second issue mentions something about cgo, which I admit I don't really understand.

So far, from what I was able to find in GitHub issues, the discussion about the missing/uneffective argument went like this

Quick question: Have you considered adding something like -fuse-ld=/path/to/your/linker, which is supported by clang. This could be useful for using non-standard linkers in case it is needed.

This is a big topic, too big to answer as a quick question

Expected Behavior

I am able to pick my own linker and ignore the zig cc's.

[jiridanek]

Sneaky workaround, if using CMake when compiling, might be to switch to clang (or gcc with ldd) to run the linker invocation

set(CMAKE_C_LINK_EXECUTABLE "clang <FLAGS> <CMAKE_C_LINK_FLAGS> <LINK_FLAGS> <OBJECTS> -o <TARGET> <LINK_LIBRARIES>")

keeping in mind that the unadulterated CMAKE_C_LINK_EXECUTABLE (on my machine) is

<CMAKE_C_COMPILER> <FLAGS> <CMAKE_C_LINK_FLAGS> <LINK_FLAGS> <OBJECTS> -o  <TARGET> <LINK_LIBRARIES>

[kassane]

Currently, Zig allows you to switch between lld or zld (WiP) using the -fno-lld/-flld flags.

• completely eliminate dependency on LLD #8726

However, with zig cc It really doesn't allow you to use the command mentioned below:

• [BUG]: Compiler Explorer uses libstdc++ with Clang by default compiler-explorer/compiler-explorer#3682 (comment)

zig: warning: argument unused during compilation: '-fuse-ld=ld' [-Wunused-command-line-argument]
zig: warning: argument unused during compilation: '-stdlib=libstdc++' [-Wunused-command-line-argument]

cc: @kubkon

[kubkon]

As a general direction, we do not want to expose -fuse-ld or -B flags to the user. Instead we would appreciate patches and issues submitted on GH.

[kubkon]

Also please note that -fno-lld and -flld are only temporary - once we support more target combinations we will always link using our linkers.

[steeve]

Just been bit by this while trying to use the mold linker, would you accept a patch implementing -fuse-ld, -B and --ld-path ?

EDIT: thinking about it, --ld-path might be the easiest and most appropriate anyhow, even arocc deprecated -B and -fuse-ld

[polarathene]

Also please note that -fno-lld and -flld are only temporary

Is ZLD meant to be compatible with zig cc?

On Fedora I often have to explicitly provide -L /usr/lib64 if I use Zig to build libraries that belong there on Fedora, yet I wouldn't normally have to provide that (such as with cargo build instead of cargo zigbuild).

---

I am curious why static linking doesn't work (seems potentially similar to this comment for mold ). If all dependencies from ldd are provided via static libs (*.a) to zig cc and ldd shows that there is nothing dynamically linked, the binary segfaults when run because it still has the system interpreter configured when it shouldn't need that. The equivalent hello world built with gcc / clang and -static works fine.

I tried both the fedora package of zig and a version from the Zig downloads page where readelf -p .comment mentions both times Clang and LLD used (slightly different version reported between the two 0.13.0 zigs), but I assume are all part of the zig binary?