Cheng Shao pushed to branch wip/wasm-command-jsval at Glasgow Haskell Compiler / GHC
Commits:
a256d3e3 by Cheng Shao at 2025-09-27T19:50:24+02:00
rts: fix wasm JSFFI initialization constructor code
This commit fixes wasm JSFFI initialization constructor code so that
the constructor is self-contained and avoids invoking a fake
__main_argc_argv function. The previous approach of reusing
__main_void logic in wasi-libc saves a tiny bit of code, at the
expense of link-time trouble whenever GHC links a wasm module without
-no-hs-main, in which case the driver-generated main function would
clash with the definition here, resulting in a linker error. It's
simply better to avoid messing with the main function, and it would
additionally allow linking wasm32-wasi command modules that does make
use of synchronous JSFFI.
- - - - -
1 changed file:
- rts/wasm/JSFFI.c
Changes:
=====================================
rts/wasm/JSFFI.c
=====================================
@@ -5,6 +5,8 @@
#include "Threads.h"
#include "sm/Sanity.h"
+#include
+
#if defined(__wasm_reference_types__)
extern HsBool rts_JSFFI_flag;
@@ -12,21 +14,8 @@ extern HsStablePtr rts_threadDelay_impl;
extern StgClosure ghczminternal_GHCziInternalziWasmziPrimziImports_raiseJSException_closure;
extern StgClosure ghczminternal_GHCziInternalziWasmziPrimziConcziInternal_threadDelay_closure;
-int __main_void(void);
-
-int __main_argc_argv(int, char*[]);
-
-int __main_argc_argv(int argc, char *argv[]) {
- RtsConfig __conf = defaultRtsConfig;
- __conf.rts_opts_enabled = RtsOptsAll;
- __conf.rts_hs_main = false;
- hs_init_ghc(&argc, &argv, __conf);
- // See Note [threadDelay on wasm] for details.
- rts_JSFFI_flag = HS_BOOL_TRUE;
- getStablePtr((StgPtr)&ghczminternal_GHCziInternalziWasmziPrimziImports_raiseJSException_closure);
- rts_threadDelay_impl = getStablePtr((StgPtr)&ghczminternal_GHCziInternalziWasmziPrimziConcziInternal_threadDelay_closure);
- return 0;
-}
+__attribute__((__weak__))
+int __main_argc_argv(int argc, char *argv[]);
// Note [JSFFI initialization]
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -66,11 +55,69 @@ int __main_argc_argv(int argc, char *argv[]) {
// by the GHC codegen, and priority 102 to the initialization logic
// here to ensure hs_init_ghc() sees everything it needs to see.
__attribute__((constructor(102))) static void __ghc_wasm_jsffi_init(void) {
- // See
- // https://gitlab.haskell.org/ghc/wasi-libc/-/blob/master/libc-bottom-half/sour...
- // for its definition. It initializes some libc state, then calls
- // __main_argc_argv defined above.
- __main_void();
+ // If linking static code without -no-hs-main, then the driver
+ // emitted main() is in charge of its own RTS initialization, so
+ // skip.
+#if !defined(__PIC__)
+ if (__main_argc_argv) {
+ return;
+ }
+#endif
+
+ // Code below is mirrored from
+ // https://gitlab.haskell.org/haskell-wasm/wasi-libc/-/blob/master/libc-bottom-...,
+ // fetches argc/argv using wasi api
+ __wasi_errno_t err;
+
+ // Get the sizes of the arrays we'll have to create to copy in the args.
+ size_t argv_buf_size;
+ size_t argc;
+ err = __wasi_args_sizes_get(&argc, &argv_buf_size);
+ if (err != __WASI_ERRNO_SUCCESS) {
+ _Exit(EX_OSERR);
+ }
+
+ // Add 1 for the NULL pointer to mark the end, and check for overflow.
+ size_t num_ptrs = argc + 1;
+ if (num_ptrs == 0) {
+ _Exit(EX_SOFTWARE);
+ }
+
+ // Allocate memory for storing the argument chars.
+ char *argv_buf = malloc(argv_buf_size);
+ if (argv_buf == NULL) {
+ _Exit(EX_SOFTWARE);
+ }
+
+ // Allocate memory for the array of pointers. This uses `calloc` both to
+ // handle overflow and to initialize the NULL pointer at the end.
+ char **argv = calloc(num_ptrs, sizeof(char *));
+ if (argv == NULL) {
+ free(argv_buf);
+ _Exit(EX_SOFTWARE);
+ }
+
+ // Fill the argument chars, and the argv array with pointers into those chars.
+ // TODO: Remove the casts on `argv_ptrs` and `argv_buf` once the witx is
+ // updated with char8 support.
+ err = __wasi_args_get((uint8_t **)argv, (uint8_t *)argv_buf);
+ if (err != __WASI_ERRNO_SUCCESS) {
+ free(argv_buf);
+ free(argv);
+ _Exit(EX_OSERR);
+ }
+
+ // Now that we have argc/argv, proceed to initialize the GHC RTS
+ RtsConfig __conf = defaultRtsConfig;
+ __conf.rts_opts_enabled = RtsOptsAll;
+ __conf.rts_hs_main = false;
+ hs_init_ghc((int *)&argc, &argv, __conf);
+ // See Note [threadDelay on wasm] for details.
+ rts_JSFFI_flag = HS_BOOL_TRUE;
+ getStablePtr((
+ StgPtr)&ghczminternal_GHCziInternalziWasmziPrimziImports_raiseJSException_closure);
+ rts_threadDelay_impl = getStablePtr((
+ StgPtr)&ghczminternal_GHCziInternalziWasmziPrimziConcziInternal_threadDelay_closure);
}
typedef __externref_t HsJSVal;
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/a256d3e33afcc65cd4e0dd921e45e4e3...
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/a256d3e33afcc65cd4e0dd921e45e4e3...
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Cheng Shao (＠TerrorJack)