| ... | ... | @@ -428,8 +428,18 @@ static LLVMValueRef make_fn_llvm_value(CodeGen *g, ZigFn *fn) { |
| 428 | 428 | // compiler as we're telling LLVM (using 'wasm-import-name' and |
| 429 | 429 | // 'wasm-import-name') what the real function name is and where to find |
| 430 | 430 | // it. |
| 431 | | const bool use_mangled_name = target_is_wasm(g->zig_target) && |
| 431 | bool use_mangled_name = target_is_wasm(g->zig_target) && |
| 432 | 432 | fn_proto->is_extern && fn_proto->lib_name != nullptr; |
| 433 | // This is subtle but important to match libc symbols at static link time correctly. |
| 434 | // We treat "c" lib_name as a special library indicating that it should be defined |
| 435 | // in libc. But if we mangle a libc symbol name here with "c" module name, then wasm-ld cannot resolve |
| 436 | // the symbol. This is because at the static link time with wasm-ld, the linker does not |
| 437 | // take module names into account, and instead looking for a pure symbol name (i.e. function name) |
| 438 | // written into the ".linking" custom section (i.e. it does not use import section). |
| 439 | // This is the intended behavior of wasm-ld, because Wasm has a concept of host functions, |
| 440 | // which are undefined functions supposed to be resolved by host runtimes *with module names* |
| 441 | // at load times even if it is "static linked" with the linker. |
| 442 | use_mangled_name = use_mangled_name && (strcmp(buf_ptr(fn_proto->lib_name), "c") != 0); |
| 433 | 443 | // Pick a weird name to avoid collisions... |
| 434 | 444 | // This whole function should be burned to the ground. |
| 435 | 445 | Buf *mangled_symbol_buf = use_mangled_name ? |
| ... | ... | @@ -452,6 +462,13 @@ static LLVMValueRef make_fn_llvm_value(CodeGen *g, ZigFn *fn) { |
| 452 | 462 | llvm_fn = LLVMAddFunction(g->module, symbol_name, fn_llvm_type); |
| 453 | 463 | |
| 454 | 464 | if (use_mangled_name) { |
| 465 | // Note that "wasm-import-module"ed symbols will not be resolved |
| 466 | // in the future version of wasm-ld since the attribute basically means that |
| 467 | // "the symbol should be resolved at load time by runtimes", though |
| 468 | // the symbol is already mangled here and it is written into "linking" section |
| 469 | // used by wasm-ld to match symbols, so it should not be expected by users. |
| 470 | // tl;dr is that users should not put the lib_name specifier on extern statements |
| 471 | // if they want to link symbols with wasm-ld. |
| 455 | 472 | addLLVMFnAttrStr(llvm_fn, "wasm-import-name", unmangled_name); |
| 456 | 473 | addLLVMFnAttrStr(llvm_fn, "wasm-import-module", buf_ptr(fn_proto->lib_name)); |
| 457 | 474 | } |
Takeshi Yoneda <takeshi@tetrate.io> 2021-07-02 15:20:17+09:00
Andrew Kelley <andrew@ziglang.org> 2021-08-31 13:39:15-07:00
src