3 ms·
TBF, that doesn't actually work - you have to write: int fd; /* fd must be declared in order to be assigned */ if ((fd = open(...)) != -1) { /* do so
by a1369209993 6y ago
TBF, that doesn't actually work - you have to write:
int fd; /* fd must be declared in order to be assigned */
if ((fd = open(...)) != -1) {
/* do something with fd */
} else {
perror("open");
}
which would be better written as:
int fd = open(...);
if (fd != -1) /* etc */
It would be nice for scoping reasons to be able to write something like:
if ((int fd = open(...)) != -1) /* etc */
but
if ((int fd == open(...)) != -1) /* etc */
isn't valid code.
- GuB-42 6y agoExactly my thoughts, I was about to comment on that but I was too lazy so I omitted the declaration. Obviously, this is HN, so someone had to point it out ;) Anyways, I am a bit torn about the second option. I like the idea of putting the call inside the if clause as it makes for a very explicit error handling but the uninitialized declaration is ugly. What I do in practice tends to depend on the situation but it is rarely satisfying. Your last suggestion would be ideal, but as you said, it is invalid code unfortunately. Maybe this for (int fd = open(...); fd != -1; fd = -1) { /* do stuff */ } Just kidding, don't do that.
- a1369209993 6y ago> for (int fd = open(...); fd != -1; fd = -1) { that doesn't correctly (or rather at all) handle the failure case. You should do (IIRC): #define LET(...) for(__VA_ARGS__,_tmp[0],*_once=_tmp; _once ;_once=0) /* ^^^ goes in a header file */ LET(int fd = open()) { if(fd == -1) { /* handle error, return or break */ } /* do stuff */ }
- saagarjha 6y agoC++17 has this! See https://en.cppreference.com/w/cpp/language/if https://en.cppreference.com/w/cpp/language/if.