Function stdio_get_stream

examples/stdlib.c:3434–3457

#define stderr  (*stdio_get_stream(STDERR_FILENO))

static __attribute__((__noinline__, __const__)) FILE **stdio_get_stream(int fd)
{
    if (fd != STDIN_FILENO && fd != STDOUT_FILENO && fd != STDERR_FILENO)
        return NULL;

    if (stdio_stream[fd] != NULL)
        return &stdio_stream[fd];

    bool r = (fd == STDIN_FILENO);
    bool w = (fd == STDOUT_FILENO || fd == STDERR_FILENO);
    int mode = (fd == STDERR_FILENO? _IONBF: _IOLBF);
    if (mutex_lock(&stdio_mutex) < 0)
        panic("failed to lock stdio stream");
    if (stdio_stream[fd] == NULL)
    {
        FILE *stream = stdio_stream_alloc(fd, r, w, mode);
        if (stream == NULL)
            panic("failed to allocate stdio stream");
        stdio_stream[fd] = stream;
    }
    mutex_unlock(&stdio_mutex);
    
    return &stdio_stream[fd];
}

static int fputc_unlocked(int c, FILE *stream)
{