RAII in C

RAII in C

systemd's way is:

void foo(void) {
    _cleanup_fclose_ FILE *f = NULL;
    ...
}

Using the following definitions:

#define _cleanup_(x) __attribute__((cleanup(x)))

static inline void fclosep(FILE **p) {
    if (*p)
        fclose(*p);
}

#define _cleanup_fclose_ _cleanup_(fclosep)

(Actually, fclosep is defined via another macro, DEFINE_TRIVIAL_CLEANUP_FUNC, but it expands to the static inline I typed above.)

Not that ugly (compare "_cleanup_fclose_ FILE *f = NULL;" with a C++ equivalent of "scoped_FILE f(nullptr);", assuming an equivalent scoped_FILE helper class). Yes, C++'s way is slightly cleaner to use (and way more complex to define), but the difference is not that big.