Re: segmentation fault with fclose

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

On 20 March 2011 22:47, bd satish wrote:
> Hi,
>
> I'm trying to close a file using fclose, but the following program seg-faults:
>
>
> #include <stdio.h>
>
> int main(void)
> {
> ? ?FILE* fp = fopen("unfounded.txt", "r");
>
> ? ?if(fp == NULL)
> ? ? ? ?fclose(fp);
>
> ? ?return 0;
> }
>
>
> The file I'm trying to open doesn't exist in the directory, so fp is
> indeed NULL. So it's just fclose(NULL).
> Is fclose(NULL) legal according to the C standard ? As an end-user I
> expect fclose(fp) to close the file (if it is already open) or just do
> nothing (if it is not open). So the seg fault -- is this a compiler
> bug ?
>
> PS: I hope this is the right place to ask this question.

It's not, this mailing list is for development of gcc, not help using
it or help with C programming questions.  Help using GCC can be sought
on the gcc-help@gcc.gnu.org mailing list but in this case you'd be
better with a general C programming forum.  Please take any follow up
questions to a more suitable place, thanks.

fclose() is provided by your system's C library, not the compiler, so
it wouldn't be a compiler bug anyway.

However fclose() requires a non-NULL pointer, so the problem is in
your code. If the file pointer is null the file wasn't opened so
there's nothing to close.