Working Dev C++ code won't work in Visual C++

[erikn]

Athar- I thought that too but before I removed the subscript I tried changing the [6] to a [10] and still got it. Definitely shouldn't have been writing out of bounds then?

[Moschops]

[10] is way, way out of bounds on something that has only six elements.

With an array of size 6 (let's call it str), the following elements are in bounds:

str[0]
str[1]
str[2]
str[3]
str[4]
str[5]

The following are out of bounds:

str[6]
str[7]
str[8]
str[9]
str[10]
str[11]
str[12]
str[13]
and so on, all the way up to str[infinity]

The following are also out of bounds:

str[-1]
str[-2]
str[-3]
str[-4]
str[-5]
str[-6]
and so on, all the way up to str[-infinity]

The debate goes on as to whether or not you should be allowed to access the null termination element on the char array data section of a std::string, but you definitely can't fiddle around with the element 4 after that.

[Cubbi]

they figured accessing the '\0' after the string is usually the result of an off-by-one error and rarely intentional. If so, they're right.

If so, they are wrong: accessing a std::string with operator[] (but not with at()) one past the end has always been perfectly legal* C++ as long as the access is read-only.

*C++98 §21.3.4[lib.string.access]/1, C++11 §21.4.5[string.access]/2

[Athar]

If so, they are wrong: accessing a std::string with operator[] (but not with at()) one past the end has always been perfectly legal* C++ as long as the access is read-only.

We already established that. That's not the point.

[erikn]

[10] is way, way out of bounds on something that has only six elements.

With an array of size 6 (let's call it str), the following elements are in bounds:

str[0]
str[1]
str[2]
str[3]
str[4]
str[5]

The following are out of bounds:

str[6]
str[7]
str[8]
str[9]
str[10]
str[11]
str[12]
str[13]
and so on, all the way up to str[infinity]

The following are also out of bounds:

str[-1]
str[-2]
str[-3]
str[-4]
str[-5]
str[-6]
and so on, all the way up to str[-infinity]

Oh. I completely misunderstood what Athar was doing with that code.

I had thought that the subscript was itself allocating memory for the string literal, so I figured [10] was "far more than enough".

But indeed, 0-5 in the subscript does not trigger the error.

[erikn]

So.... not too many VC++2010 users around here, ay?

[Peter87]

If so, they are wrong: accessing a std::string with operator[] (but not with at()) one past the end has always been perfectly legal* C++ as long as the access is read-only.

C++03 they say

Returns: If pos < size(), returns data()[pos]. Otherwise, if pos == size(), the const version returns charT(). Otherwise, the behavior is undefined.

So only the const version is defined. This should work fine

#include <string>
int main()
{
	const std::string str("Hello!");
	str[6];
}

[Cubbi]

@Peter87 indeed, Visual Studio 2010 SP1 conforms to C++03 in that respect (not C++11 though). Nevermind my comment.

[erikn]

dying to let this thread sail off into oblivion at this point, but since it's already at the top just wanted to thank you guys for your time and patience.