Re: Using STL(map) inside of C data structure. How?

From:

Mathias Gaunard <loufoque@gmail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Wed, 29 Aug 2007 13:59:07 CST

Message-ID:

<1188395680.826829.316960@22g2000hsm.googlegroups.com>

On Aug 29, 3:07 pm, Andrew Trapani <andrewtrap...@gmail.com> wrote:

#include <map>
#include anything else necessary

typedef struct {
std::map<const char*, int> m;

} sType;

int main(int argc, char **argv) {
numberOfStructs = 5;
sType s = (sType*) malloc(sizeof(sType) * numberOfStructs);
s.m.empty(); /* seg faults here */

}

Is this possible? Thanks.

This code can't compile. I will assume you did typos and meant

sType* s = (sType*) malloc(...);
s->m.empty();

You probably get a segfault because you didn't call the constructor of
sType, (which calls the constructor of std::map). You will also need
to call the destructor before freeing memory.

Plus, you haven't checked whether malloc returned NULL or not.

And finally, it is obvious it would be way easier to use new.

sType* s = new sType[5];
s->m.empty();

then delete[] s;

Even better, use auto_ptr or similar for your code to be exception-
safe and free of explicit deletes.

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