Use MUSL's `weak*` feature in bottom half (#306)

[wasi-libc.git] / libc-bottom-half / sources / environ.c

#include <unistd.h>
#include <stdlib.h>
#include <sysexits.h>
#include <wasi/api.h>
#include <wasi/libc.h>
#include <wasi/libc-environ.h>

// If the program does use `environ`, it'll get this version of
// `__wasilibc_environ`, which is initialized with a constructor function, so
// that it's initialized whenever user code might want to access it.
char **__wasilibc_environ;
weak_alias(__wasilibc_environ, _environ);
weak_alias(__wasilibc_environ, environ);

// We define this function here in the same source file as
// `__wasilibc_environ`, so that this function is called in iff environment
// variable support is used.
// Concerning the 50 -- levels up to 100 are reserved for the implementation,
// so we an arbitrary number in the middle of the range to allow other
// reserved things to go before or after.
__attribute__((constructor(50)))
static void __wasilibc_initialize_environ_eagerly(void) {
    __wasilibc_initialize_environ();
}

// See the comments in libc-environ.h.
void __wasilibc_maybe_reinitialize_environ_eagerly(void) {
    // This translation unit is linked in if `environ` is used, meaning we need
    // to eagerly reinitialize the environment variables.
    __wasilibc_initialize_environ();
}