pyt@hprnd.HP.COM (Pierre-Yves Thoulon) (11/01/88)
I've recently had trouble with the realloc function in the Microsoft C
v5.1 small model run-time library: for a reason yet unknown to me, it
hangs, being caught in an infinite loop (I could track it down to the
assembly language level with CodeView).
Below is a small program that is guaranteed to catch the problem.
What it does is basically the following:
* allocate space for an array of 24 byte structures
* copy some stuff (garbage actually...) to the allocated space
* reallocate a larger space for the same array (24 more bytes)
* copy some stuff to the newly allocated space
* etc...
For whatever reason the pointer returned by realloc changes every time
realloc is called. After something like 5 to 10 iterations, realloc
hangs. Alt-Ctl-Del is the only means of getting things back into control.
Has anyone seen this problem ? Does anybody have a working realloc function ?
Or am I missing something (I'm new to MSC and the realloc function...) ?
Any help appreciated.
Thanks,
Pierre-Yves THOULON.
-----------------------------cut here-----------------------------------
#include <dos.h>
#include <malloc.h>
#include <stdio.h>
#include <string.h>
struct FileInfo
{
char Dummy0; /* so that the unsigned be correctly aligned on
a word boudary */
char Attrib;
unsigned WrTime;
unsigned WrDate;
long Size;
char Name[13];
char Dummy1; /* so that the next structure in the array be
correctly aligned on a word boundary */
};
void GetFileList(void)
{
struct FileInfo *Files;
struct find_t DosReturn;
int FileNum = 0;
Files=NULL;
for(;;)
{
printf("FileNum = %4d, Files = %5u\n",FileNum,Files);
/*
* [Re]allocate space for the structure array.
* Below is the faulty realloc that hangs (sometimes...)
* I know it's not really efficient to allocate 24 bytes at
* a time, but that's the best way to have it hang...
*/
if ((Files = (struct FileInfo *)realloc(Files,(FileNum + 1) * sizeof(struct FileInfo))) == NULL)
{
printf("Cannot reallocate memory");
exit(-1);
}
/*
* Copy the (uninitialized...) DosReturn structure to the
* newly allocated space
*/
memcpy(&Files[FileNum++].Attrib,&DosReturn.attrib,sizeof(struct FileInfo));
}
}
/**********************************************************************
*
* Function : main
*
**********************************************************************/
main()
{
GetFileList();
}