Problem with the free up the memory in c

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my task is create a memory for pointer in dynamic library

and free up the memory of allocated in the main function..

i can do create and free the memory in same side..
but i can't perform the operation in vice versa..

my library function code:

DYNAMICLIB_API int* aa1(void)
{
    int *a1;
    a1=(int*)malloc(sizeof(int));
    printf("Interger created\n");
    printf("bye");
    printf("good");
    printf("memory created");
    free(a1);
    return a1;
}

my main function code:
int main(int argc, char* argv[])
{
    int *a1;
    a1=aa1();
    printf("Hello World!\n");
    free(a1);
    return 0;
}

the free function provide the run time error.. can you help me

[edit]Code block added - OriginalGriff[/edit]

Posted 5-Jul-11 1:05am

@BangIndia

Updated 5-Jul-11 1:06am

OriginalGriff

v2

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Prerak Patel 5-Jul-11 7:11am

What is the error?

1 solution

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OriginalGriff · Answer 1 · 2011-07-05T01:10:00

Solution 1

I'm not surprised - you are returning a pointer to memory you have already freed:

free(a1);
return a1;

Then, you try to free it again!

Bad idea - never, ever return a pointer to anything unless you allocated it, and haven't freed it. That includes things like this:

int* GetBadPointer(void)
   {
   int i = 76;
   return &i;
   }

It will always blow up in your face at some point, normally when you don't expect it, unless you are very careful with your pointers!

Posted 5-Jul-11 1:10am

OriginalGriff

Comments

@BangIndia 5-Jul-11 7:17am

sorry sir..

DYNAMICLIB_API int* aa1(void)
{
int *a1;
a1=(int*)malloc(sizeof(int));
printf("Interger created\n");
printf("bye");
printf("good");
printf("memory created");
return a1;
}
now also not coming the output . what i do.. now

OriginalGriff 5-Jul-11 10:25am

If I try your code through a boring ANSI C compiler I have to remove the DYNAMICLIB_API and it works fine.

What is the DYNAMICLIB_API bit and have your tried to remove it?

@BangIndia 6-Jul-11 0:54am

i create a dynamic library for creating the memory..
and i use the main function to free that memory.