Andrew Pinski - Re: Abnormal behavior of malloc in gcc-3.2.2 (original) (raw)

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• From: Andrew Pinski
• To: sandeepksinha at gmail dot com (Sandeep Kumar)
• Cc: gcc at gcc dot gnu dot org
• Date: Mon, 21 Nov 2005 00:02:24 -0500 (EST)
• Subject: Re: Abnormal behavior of malloc in gcc-3.2.2

Hi Everyone,

int main () { int *p; int i;

p = (int *) malloc (400 * sizeof (int));
for (i = 0; i < 512; i++)
 {
     p[i] = i;
     printf ("p[%d]: %d\n", i, p[i]);
 }

return 0; }

The following code should terminate with Segmentation fault, right ? But when I tried, it works even beyond the limits of allocated area ... I am using Glibc - 2.3.2-11.9 , gcc - 3.2.2

Is it a bug - malloc's implementation in Glibc. Does malloc allocates a complete 4k page for certain size of memory asked for?

Infact, it gives a segmentation fault at 1681 location => p[1681]: 1681 Segmentation fault

Or is it using Heap area ?

First why do you think this is a GCC bug? Second you are invoking undefined behavior by accessing passed the array bounds (or allocated bounds by malloc).

-- Pinski

• Follow-Ups:
  • Re: Abnormal behavior of malloc in gcc-3.2.2
    * From: Sandeep Kumar
• References:
  • Abnormal behavior of malloc in gcc-3.2.2
    * From: Sandeep Kumar