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malloc & free problem

Started by tordyvel Jun 6, 2002 at 9:00 PM 5 replies 200+ views

Original Post

Jun 6, 2002 at 9:00 PM

This code crashes when I run it but I can''t find anything wrong. If I remove the free(Data); line or the loops that fills the array it doesn''t crash. please help me.

  
	USHORT *Data;

	int iWidth = 50;
	int iHeight = 50;

	int newSize = iWidth*iHeight;

	Data = (USHORT*)malloc(newSize);

	for(y=0;y<iHeight;y++)
		for(int x=0;x<iWidth;x++)
			Data = (USHORT*)5000;
	if(Data)				
		free(Data);
	Data = NULL;

Colin Jeanne

Jun 6, 2002 at 9:07 PM

Instead of Data = (USHORT*)5000 you could write Data[x + y * iWidth] = 5000;

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DerekSaw

Jun 6, 2002 at 9:09 PM

Your problem started when....
...your code changes where Data points to. Instead of Data pointing to the memory you just allocated for it, you change it to point else where (5000?). And when you free it, you are freeing something that is not even allocated.

Just try any of the suggested solution should correct the problem.

[edited by - DerekSaw on June 6, 2002 10:12:34 PM]

IndirectX

Jun 6, 2002 at 9:19 PM

Besides, you should be malloc''ing newSize*sizeof(USHORT), because malloc''s parameter is the number of bytes to allocate, not the number of items in an array as it is for new.

tordyvel

Jun 6, 2002 at 9:25 PM

Thanks for all your help!
I didn''t know that thing about malloc and new

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