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Code Issues 1 Releases Wiki Activity

Address #1037 - move stack hack after arg writing logic to avoid

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clobber.
This commit is contained in:
bakpakin 2022-09-20 15:36:03 -05:00
parent 1cebe64664
commit 43c47ac44c
2 changed files with 7 additions and 2 deletions
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1
examples/ffi/so.c
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@ -154,6 +154,7 @@ void void_ret_fn(int x) {
EXPORTER
int intintint_fn_2(intintint iii, int i) {
fprintf(stderr, "iii.a = %d, iii.b = %d, iii.c = %d, i = %d\n", iii.a, iii.b, iii.c, i);
return i * (iii.a + iii.b + iii.c);
}

8
src/core/ffi.c
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@ -1093,8 +1093,8 @@ static Janet janet_ffi_win64(JanetFFISignature *signature, void *function_pointe
ret_mem = alloca(type_size(signature->ret.type));
regs[0].integer = (uint64_t) ret_mem;
}
uint64_t *stack = alloca(signature->stack_count * 8);
stack -= 2; /* hack to get proper stack placement */
size_t stack_size = signature->stack_count * 8;
uint64_t *stack = alloca(stack_size);
for (uint32_t i = 0; i < signature->arg_count; i++) {
int32_t n = i + 2;
JanetFFIMapping arg = signature->args[i];
@ -1113,6 +1113,10 @@ static Janet janet_ffi_win64(JanetFFISignature *signature, void *function_pointe
}
}
/* hack to get proper stack placement and avoid clobbering from logic above - shift stack down, otherwise we have issues.
* Technically, this writes into 16 bytes of unallocated stack memory */
if (stack_size) memmove(stack - 2, stack, stack_size);
switch (signature->variant) {
default:
janet_panicf("unknown variant %d", signature->variant);