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Basically copy-and-paste from: https://github.com/yamt/garbage/tree/master/wasm/longjmp While it seems working well, it's disabled by default because: * It might be controversial if it's a good idea to use this emscripten API for WASI as well. * LLVM produces bytecode for an old version of the EH proposal. * The EH proposal is not widely implemeted in runtimes yet.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,2 @@ | ||
| /* note: right now, only the first word is actually used */ | ||
| typedef unsigned long __jmp_buf[8]; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,90 @@ | ||
| /* | ||
| * https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp | ||
| */ | ||
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||
| #include <stdint.h> | ||
| #include <stdlib.h> | ||
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| struct entry { | ||
| uint32_t id; | ||
| uint32_t label; | ||
| }; | ||
|
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| static _Thread_local struct state { | ||
| uint32_t id; | ||
| uint32_t size; | ||
| struct arg { | ||
| void *env; | ||
| int val; | ||
| } arg; | ||
| } g_state; | ||
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| /* | ||
| * table is allocated at the entry of functions which call setjmp. | ||
| * | ||
| * table = malloc(40); | ||
| * size = 4; | ||
| * *(int *)table = 0; | ||
| */ | ||
| _Static_assert(sizeof(struct entry) * (4 + 1) <= 40, "entry size"); | ||
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| void * | ||
| saveSetjmp(void *env, uint32_t label, void *table, uint32_t size) | ||
| { | ||
| struct state *state = &g_state; | ||
| struct entry *e = table; | ||
| uint32_t i; | ||
| for (i = 0; i < size; i++) { | ||
| if (e[i].id == 0) { | ||
| uint32_t id = ++state->id; | ||
| *(uint32_t *)env = id; | ||
| e[i].id = id; | ||
| e[i].label = label; | ||
| /* | ||
| * note: only the first word is zero-initialized | ||
| * by the caller. | ||
| */ | ||
| e[i + 1].id = 0; | ||
| goto done; | ||
| } | ||
| } | ||
| size *= 2; | ||
| void *p = realloc(table, sizeof(*e) * (size + 1)); | ||
| if (p == NULL) { | ||
| __builtin_trap(); | ||
| } | ||
| table = p; | ||
| done: | ||
| state->size = size; | ||
| return table; | ||
| } | ||
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| uint32_t | ||
| testSetjmp(unsigned int id, void *table, uint32_t size) | ||
| { | ||
| struct entry *e = table; | ||
| uint32_t i; | ||
| for (i = 0; i < size; i++) { | ||
| if (e[i].id == id) { | ||
| return e[i].label; | ||
| } | ||
| } | ||
| return 0; | ||
| } | ||
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| uint32_t | ||
| getTempRet0() | ||
| { | ||
| struct state *state = &g_state; | ||
| return state->size; | ||
| } | ||
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| void | ||
| __wasm_longjmp(void *env, int val) | ||
| { | ||
| struct state *state = &g_state; | ||
| struct arg *arg = &state->arg; | ||
| arg->env = env; | ||
| arg->val = val; | ||
| __builtin_wasm_throw(1, arg); | ||
| } |