Why does istream::operator>> accept char pointers/arrays?

Question

char someArray[n];
std::cin >> someArray; // potential buffer overrun

I've seen code like the above numerous times on the C++ forums I frequent. Is there a good reason for this not to be treated as a compile time error? or at the very least, a warning?

Relevant [Bjarne's quote and discussion](http://programmers.stackexchange.com/q/92126/47504). — vvnraman, Nov 06 '12 at 02:31
It's a non-issue, because you wouldn't use naked C arrays like that in real C++ anyway. — Kerrek SB, Nov 06 '12 at 02:51

score 4 · Answer 1 · answered Nov 06 '12 at 02:27

An underlying premise with C (and C++) is that the coder should know what they're doing. Otherwise they'd be coding in BASIC :-)

It's not permitted to be an error since it's allowed per the standard, just like gets and scanf("%s") are allowed in C, despite the fact they're a problem waiting to happen.

The code you've posted is bad and has no place in serious software, but it's fine for "toy" programs or testing things. You just need to be aware of its problems (and it sounds very much like you are aware of them).

And it is probably intended to make it easier when using C-style strings. — Arafangion, Nov 06 '12 at 02:29

score 0 · Answer 2 · answered Nov 06 '12 at 03:02

If C++ had been all been invented in one fell swoop, it probably wouldn't exist at all -- if you wanted to read a string, you'd have to read it into a std::string, and that would be the end of it.

Unfortunately, C++ was used for quite a while before std::string was standardized (or invented at all). Both operator>> and istream::getline (not to be mistaken for std::getline) were invented during that time. When they were invented, there was little (or no) real alternative, so they worked with arrays of char.

Today, of course, there are alternatives, and it's best to just avoid these unless you get stuck writing code with some ancient compiler that doesn't support the superior alternatives.

Why does istream::operator>> accept char pointers/arrays?

2 Answers2