[WebAssembly] mysterious imports of aliases

[yamt]

i noticed a lot of mysterious imports in wasi-libc libc.so. the following is a smaller example of the symptom.

alias.c:

int
add1(int x)
{
        return x + 1;
}

extern int add1_alias(int x)
        __attribute__((visibility("default"), weak, alias("add1")));

build it with:

clang -nostdlib -shared -Wl,--no-entry -o lib.so alias.c

look at the generated lib.so, see env.add1_alias import.

Import[6]:
 - memory[0] pages: initial=0 <- env.memory
 - table[0] type=funcref initial=0 <- env.__indirect_function_table
 - global[0] i32 mutable=1 <- env.__stack_pointer
 - global[1] i32 mutable=0 <- env.__memory_base
 - global[2] i32 mutable=0 <- env.__table_base
 - func[0] sig=0 <add1_alias> <- env.add1_alias

i don't see any obvious reasons to import this symbol. actually, the imported function doesn't seem to be used within the module at all.

fwiw, the export sections of the module look like:

Export[2]:
 - func[2] <__wasm_apply_data_relocs> -> "__wasm_apply_data_relocs"
 - func[3] <add1> -> "add1_alias"

[llvmbot]

@llvm/issue-subscribers-backend-webassembly

Author: YAMAMOTO Takashi (yamt)

i noticed a lot of mysterious imports in wasi-libc libc.so. the following is a smaller example of the symptom. alias.c: ```c int add1(int x) { return x + 1; } extern int add1_alias(int x) __attribute__((visibility("default"), weak, alias("add1"))); ``` build it with: ```shell clang -nostdlib -shared -Wl,--no-entry -o lib.so alias.c ``` look at the generated lib.so, see `env.add1_alias` import. ``` Import[6]: - memory[0] pages: initial=0 <- env.memory - table[0] type=funcref initial=0 <- env.__indirect_function_table - global[0] i32 mutable=1 <- env.__stack_pointer - global[1] i32 mutable=0 <- env.__memory_base - global[2] i32 mutable=0 <- env.__table_base - func[0] sig=0 <add1_alias> <- env.add1_alias ``` i don't see any obvious reasons to import this symbol. actually, the imported function doesn't seem to be used within the module at all. fwiw, the export sections of the module look like: ``` Export[2]: - func[2] <__wasm_apply_data_relocs> -> "__wasm_apply_data_relocs" - func[3] <add1> -> "add1_alias" ```

[ppenzin]

These help simulate POSIX and they should be documented in tool conventions. I did a brief check, at least some of them are.

[yamt]

These help simulate POSIX and they should be documented in tool conventions. I did a brief check, at least some of them are.

can you pinpoint the relevant part of tool-conventions?