Every export in WebAssembly is removed in ldc 1.15.0-beta1

[skoppe]

In ldc 1.14 and before, any function marked with extern(C) export was exported in the wasm binary.

With ldc 1.15-beta1 pretty much everything is stripped. The only way I can export anything is to pass --export=funcname to the linker.

Ironically in ldc 1.14 the hard part was to remove exports (since it was exporting way too much, including *init_Z), but in ldc 1.15-beta1 all that stuff is removed (yay!), but also the things I want to export.

[skoppe]

Here is the relevant section from lld

When building an executable, only the entry point and symbols flagged as WASM_SYMBOL_EXPORTED are exported by default. In LLVM the WASM_SYMBOL_EXPORTED flag is applied to any symbol in the llvm.used list which corresponds to attribute((used)) in C/C++ sources.

In addition, symbols can be exported via the linker command line using --export.

Finally, just like with native ELF linker the --export-dynamic flag can be used to export symbol in the executable which are marked as visibility=default.

If I add --export-dynamicto the linker I get the same behaviour as with ldc 1.14

But, is there a way I can add the __attribute__((used)) to my function?

[kinke]

Sure: https://github.com/ldc-developers/druntime/blob/3a42b95d449ed2704c8a1d8027c9388fe3e15c8a/src/ldc/attributes.d#L73

[skoppe]

Nice. I see in the llir that it is correct:

@llvm.used = appending global [1 x i8*] [i8* bitcast (i8* (i32)* @allocString to i8*)], section "llvm.metadata" ; [#uses = 0]

except it still doesn't get exported.

I am not sure what version of llvm ldc uses. It could be that the change I am waiting for (https://reviews.llvm.org/D57869) is still in the pipeline.

[kinke]

I am not sure what version of llvm ldc uses.

8.0.0-rc4 as mentioned in the release notes. That change is very fresh, so very likely not to be part of LLVM 8 (which was branched off trunk mid-January).

[skoppe]

Ok. I am going to use --export-dynamic until that change is released. Thanks for the quick replies.