Junio C Hamano <gitster@xxxxxxxxx> writes:
>> How about (this ugly code):
>>
>> packet_trace("0000", sizeof "0000" - 1, 1);
>> if (write_in_full(fd, "0000", sizeof "0000" - 1) < 0)
>
> Yeah, that is ugly. I was thinking more in the direction of
> replacing these three-argument write_in_full with something like
>
> #define write_constant(fd, constant_string) \
> write_in_full((fd), (constant_string), strlen(constant_string))
>
> with some preprocessor magic to make the compilation break when the
> second parameter to the macro is not a string constant.
There is a bit of subtlety but I did mean C preprocessor macro and
not a helper function with the above. With use of a macro defined
like above, the programmer can write
write_constant(fd, "0000");
which would turn into
write_in_full((fd), "0000", strlen("0000"));
Descent compilers know to produce identical code as
write_in_full((fd), "0000", 4);
when seeing a literal constant string given to strlen().
But a helper function like this:
static int write_constant(int fd, const char *string) {
return write_in_full(fd, string, strlen(string));
}
has less chance of getting the same kind of optimization (the helper
needs to be inlined before the compiler can realize that the
parameter to strlen() is a literal constant whose length can be
computed at the compile time).
