std::ptrdiff_t' has not been declared

Question

I have made my own source file, and I'm trying to add stddef.h. At compiling I have the following error:

std::ptrdiff_t' has not been declared.

What I've done wrong?

Have you tried including [``](http://en.cppreference.com/w/cpp/header/cstddef) instead? — Some programmer dude, Sep 29 '16 at 12:04
@Joachim Pileborg , yes, i've tried to include cstddef, but - I need libraries in my project from matlab simulink coder, which requires stddef.h.... — infernalcucumber, Sep 29 '16 at 12:24
Using smartphone, It took me 5 seconds to google it: http://en.cppreference.com/w/cpp/types/ptrdiff_t just include — masoud, Sep 29 '16 at 12:26

score 3 · Accepted Answer · answered Sep 29 '16 at 12:37

3

The problem is that you are including the standard C header, not the standard C++ header.

The standard C header will not put their symbols in the std namespace, since C doesn't have such things.

That you have other applications requiring the C header doesn't matter, if you want to use the ptrdiff_t type-alias from the C++ std namespace, you must include <cstddef>.

Or stop using std::ptrdiff_t and user the unqualified and global ptrdiff_t from <stddef.h>.

answered Sep 29 '16 at 12:37

Some programmer dude

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@infernalcucumber Yes. – Some programmer dude Sep 29 '16 at 13:10
I know, I'm newbie at programing, but do you mean that if I'll include , it should work properly with libraries which are requiring stddef.h ? – infernalcucumber Sep 29 '16 at 13:14
I've include instead of , but when i've include libraries generated from matlab simulink coder, at compiling I have following error again: 'std::ptrdiff_t' has not been declared line 72, external location: D:\QNX650\target\qnx6\usr\include\stddef.h – infernalcucumber Sep 29 '16 at 13:19

std::ptrdiff_t' has not been declared

1 Answers1