Wrong table index for function pointers when dynamically linking for wasm32-wasi #170910
Description
Hello everyone!
I am currently experimenting with dynamic linking for wasm32-wasi (p1).
The C code below crashes at runtime for the second case in the main routine (when compiled with -Wl,-fPIC -Wl,-shared).
I could pinpoint the problem a bit: When you pass a function pointer to a designated initializer of a C struct the __table_base (offset for the function index) is not added yielding a wrong table index for the function. The table index is correct, when I use the function pointer directly (see first case).
When I use any optimisation other than -O0, the problem goes away for this simple test. However, when I try to compile a larger code base with many pointers in many structs, it does fail again even with -O[1-3].
I am using clang version 21.1.4-wasi-sdk.
Any ideas how to fix or circumvent the problem would be highly appreciated!
Thank you for your great work!
#include <stdio.h>
static void apply_func(void (*f)(int), int x) {
f(x);
}
static void func(int x) {
printf("func(%d)\n", x);
}
typedef struct func_struct func_struct;
struct func_struct {
void (*f)(int);
};
int main(void) {
// (1) this does work:
apply_func(func, 42);
// (2) this does NOT work:
static func_struct fs = { func };
apply_func(fs.f, 42);
return 0;
}