WebAssembly tables + global variables + debug info = invalid binaries

[feedab1e]

creating a WebAssembly table and another global variable, then compiling with debug info, yields a binary that cannot be read or linked by any llvm tool (link):

// 1.cpp
int a;
inline static __externref_t table[0];

int main() {
    __externref_t get();
    __builtin_wasm_table_set(table, 0, get());
}

if compiled with

clang++ -g --target=wasm32 1.cpp -c -o 1.o

and used like following:

llvm-dwarfdump 1.o

will yield

error: 1.o: invalid data relocation: _ZL5table

The same issue occurs when trying to link:

wasm-ld --no-entry 1.o -o 1.wasm

yields

wasm-ld: error: 1.o: invalid data relocation: _ZL5table

Notably, the same issue does not occur when we remove the declaration of a:

// 1.cpp
inline static __externref_t table[0];

int main() {
    __externref_t get();
    __builtin_wasm_table_set(table, 0, get());
}

links successfully.

[llvmbot]

@llvm/issue-subscribers-backend-webassembly

Author: None (feedab1e)

creating a WebAssembly table and another global variable, then compiling with debug info, yields a binary that cannot be read or linked by any llvm tool ([link](https://gcc.godbolt.org/z/hP5dPq5qx)): ```cpp // 1.cpp int a; inline static __externref_t table[0];

int main() {
__externref_t get();
__builtin_wasm_table_set(table, 0, get());
}

if compiled with

clang++ -g --target=wasm32 1.cpp -c -o 1.o

and used like following:

llvm-dwarfdump 1.o

will yield

error: 1.o: invalid data relocation: _ZL5table

The same issue occurs when trying to link:

wasm-ld --no-entry 1.o -o 1.wasm

yields

wasm-ld: error: 1.o: invalid data relocation: _ZL5table

Notably, the same issue does not occur when we remove the declaration of `a`:

// 1.cpp
inline static __externref_t table[0];

int main() {
__externref_t get();
__builtin_wasm_table_set(table, 0, get());
}

links successfully.
</details>

[sbc100]

Not much work has been done on supporting externref / table over the last year or so. If you are using this feature perhaps you would be able to work on it? I don't know of anyone currently using it or working on it.