AStrangeFunction_test.cpp

static int aStrangeFunction() {
	return ({ std::string xxx{"the answer is"}; 42; });
}

TEST(AStrangeFunction, AlwaysReturnTheAnswer) {
	ASSERT_EQ(42, aStrangeFunction());
}

common.h

#define sys_errmsg(fmt, ...)  ({                                            \
	int _err = errno;                                                   \
	errmsg(fmt, ##__VA_ARGS__);                                         \
	fprintf(stderr, "%*serror %d (%s)\n", (int)sizeof(PROGRAM_NAME) + 1,\
		"", _err, strerror(_err));                                  \
	-1;                                                                 \
})

libubi.c

static int read_positive_ll(const char *file, long long *value)
{
	// ...

	if (close(fd))
		return sys_errmsg("close failed on \"%s\"", file);

	return 0;

out_error:
	close(fd);
	return -1;
}