Re: Returning a struct from a function - strange behavior

DiAvOl wrote:

#include <stdio.h>

typedef struct person {
char name[40];
int age;
} Person;

static Person make_person(void);

int main(void) {
printf("%s\n", make_person().name);
return 0;
}

static Person make_person(void) {
static Person p = { "alexander", 18 };
return p;
}

The above small program when compiled without the -std=c99 option
(using gcc 4.2.3) gives me a warning:
"warning: format ?%s? expects type ?char *?, but argument 2 has
type ?char[40]?"
and also fails with a segmentation fault when executed.

If I replace the line printf("%s\n", make_person().name); with
printf("%s\n", &make_person().name[0]); everything works as
expected.

Why does this happen? Isn't make_person().name a pointer to the
array's first element?

No. make_person() returns a struct by value, which has a field
identified by .name. That field is an array of 40 chars. It is a
portion of the return struct, which has never been put in
accessible memory.

Your alleged 'good' experience with lcc shows a bug in lcc. I
don't know if you mean lcc-win32 (which has quite a few known
insects) or lcc (which is less well known here).

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
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