[PATCH] D79248: [lld][WebAssembly] Implement --unresolved-symbols

[Sam Clegg via Phabricator via llvm-commits]

sbc100 added a comment.

In D79248#2396409 <https://reviews.llvm.org/D79248#2396409>, @MaskRay wrote:

> In ELF, `--unresolved-symbols=` sets `--[no-]allow-shlib-undefined` and `-z (un)defs` simultaneously.
>
> - `--[no-]allow-shlib-undefined`: whether an unresolved undefined symbol from a shared object should be errored
> - `-z (un)defs`:  whether an unresolved undefined symbol from a regular object should be errored.
>
> Does the wasm usage fit well in the existing practice?

The support for shared libraries in wasm-ld, and indeed the entire PIC ABI,  is experimental (in fact, it will warn until you also pass `--experimental-pic`).

In particular, support for linking against shared libraries does not yet

In D79248#2396409 <https://reviews.llvm.org/D79248#2396409>, @MaskRay wrote:

> In ELF, `--unresolved-symbols=` sets `--[no-]allow-shlib-undefined` and `-z (un)defs` simultaneously.
>
> - `--[no-]allow-shlib-undefined`: whether an unresolved undefined symbol from a shared object should be errored
> - `-z (un)defs`:  whether an unresolved undefined symbol from a regular object should be errored.
>
> Does the wasm usage fit well in the existing practice?

Yes.   While we don't currently support either of those flags I believe the implementation of `ignore-all` here will match `-z defs`, so I think that adding support for `-z (un)defs` would be trivial if decide do add that flag in the future.

Regarding  `--[no-]allow-shlib-undefined`, our shared library support is still experimental is rather limited.  Using it currently requires the `--experimental-pic` flag.

BTW, looking at the ELF code I don't see `--unresolved-symbols` currently effecting `--allow-shlib-undefined.

In ELF/Driver.cpp we have:

  config->allowShlibUndefined =                                                  
        args.hasFlag(OPT_allow_shlib_undefined, OPT_no_allow_shlib_undefined,                        
                     args.hasArg(OPT_shared));

And this doesn't look like it gets updated based on `--unresolved-symbols`.


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https://reviews.llvm.org/D79248