[PATCH] D76547: [WebAssembly] Add `wasm-exported` function attribute

Wed Mar 29 10:46:03 PDT 2023

sbc100 added a comment.

The reason `__attribute__((export_name("foo")))` doesn't work in all use cases is that we have a lot of existing code that uses the `EMSCRIPTEN_KEEPALIVE` macro.     We also have run into other folks who want to include this is some kind of `FOO_API`, or `EXPORT_API` type macros.  Its not possible to have such a macro map to the existing export_name since they don't include the symbol name: e.g:

  EMSCRIPTEN_KEEPALIVE int foo();`

  JNI_EXPORT int myfunct();

In these cases we need something that uses the llvm symbol name for the export.

However, as I mention in my earlier comment I have since realized that these attributes cannot be applies the llvm GlobalValues in general only the Functions... and the idea behind EMSCRIPTEN_KEEPALIVE is that it can be used to tag both functions and data symbols (addresses).

Sadly I don't see any way to attach attributes to data symbols in llvm today..  we have visibility but not attribute bag :(

================
Comment at: clang/lib/Sema/SemaDeclAttr.cpp:7572
+  if (FD->isThisDeclarationADefinition()) {
+    S.Diag(D->getLocation(), diag::err_alias_is_definition) << FD << 0;
+    return;
----------------
aaron.ballman wrote:
> Is this diagnostic actually correct? It's for use with the alias and ifunc attributes, so I'm surprised to see it here.
It does look incorrect yes, this is copy-pasted from the exist `ExportNameAttr` so I guess that is wrong too. 

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D76547/new/

https://reviews.llvm.org/D76547