Question

I am trying to use a malloc of short, something like

typedef union _SOME_STRUCT_ {

   struct {

     USHORT u:4;
     USHORT v:4;
     USHORT w:4;

   } x;

   USHORT word;

} SOME_STRUCT, *PSOME_STRUCT;

PSOME_STRUCT p = malloc (sizeof (SOME_STRUCT));

if (p) {

    p->x.u = 0;
}

free (p); // **** RANDOMLY CRASHING HERE ****

I am debugging for a couple of days and clueless,

Note(edited): Linux, and gcc Version 3.4.6 20060404

---

ISSUE FOUND USING VALGRIND

But then, I would like to document it here so that my fellow developers might be aware of such a situation …

I had actually defined the structure as

typedef union _SOME_STRUCT_ {

   struct {

     USHORT u:4;
     USHORT v:4;
     USHORT w:4;

   } x;

   USHORT word;

} ALBUM, *PALBUM;

and some-where else in the code I had also defined

#define ALBUM "album"

And so, sizeof (ALBUM) was referring to the #define value rather than the typedef and hence the issue.

The thing that amazes me is,

Is this allowed in C?

---

Answer 1

Try to pass your program through valgrind , an open source program and totaly free, maybe it could help you to see where is the issue. Don’t forget to compile with debug symbols: gcc -g [etc] .

Hope this help..