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Comment by tptacek | Hacker News Reader

Can you tell a story about how NULL bit you in the ass in real code?

I remember one early version of a C++ compiler which had NULL #defined as (( void* )0), which caused all manner of fun trying to compile some legacy C code.

This was in 1999, I think.

You mean like this?

#define NULL __DARWIN_NULL

...

#define __DARWIN_NULL ((void *)0)

Something like that. It makes the following invalid in C++ but valid in C:

  int *ptr = NULL;

Except for the fact that the real definition is actually more like:

    #ifdef __cplusplus
    #define __DARWIN_NULL __null
    #else /* ! __cplusplus */
    #define __DARWIN_NULL ((void *)0)
    #endif /* __cplusplus */

So the code you mentioned works just fine in C++.

Except that the actual compiler I was using was for the PlayStation 2, so I very much doubt it had that precise code you just outlined, and it really did have NULL defined as ((void* )0), and it really did break. I saw it happen.

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