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fwrite throws segmentation fault

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# 1  
Old 08-25-2005
fwrite throws segmentation fault
Code : function sSaveTFFile
Code:
             .......................
	iRetCode = link (caCurrentFilename, caBackupFilename);
	if (iRetCode == -1)
	{
		ERR_MSG2(LOG_ALERT, "Can't move %s to %s", caCurrentFilename, caBackupFilename);
		return(FAILURE);
	}
	
	iRetCode = unlink (caCurrentFilename);
	if (iRetCode == -1)
	{
		ERR_MSG2(LOG_ALERT, "Can't move %s to %s", caCurrentFilename, caBackupFilename);
		return(FAILURE);
	}


	fpTFFile = fopen (caCurrentFilename, "wb"); 
	if (fpTFFile == NULL)
	{
		ERR_MSG1 (LOG_ALERT, "Can't open %s\n", caCurrentFilename);
		return (FAILURE);
	}

/*
the program crashes here while calling the fwrite function. 
I have verified all the parameters of fwrite. They are valid pointers.  I've also tried putting another fwrite function writing a hard coded value into a file. That function also is crashing.
I've replaced fwrite with fprintf, but still getting the same error.
*/
	if (fwrite (pCurSectData->pucData, sizeof (Uchar_t), pCurSectData->ulDataSize, fpTFFile)
		!= pCurSectData->ulDataSize)
	{
		ERR_MSG1 (LOG_ALERT, "Can't save modified TF data to %s\n", caCurrentFilename);
		return (FAILURE);
	}

             ................................

please find the snapshot of the call stack (while the crash has occurred) in the attachement


Here our function is sSaveTFFile, which calls the fwrite and it is throwing the segmentation fault.

While searching in Google Groups, I found some articles telling the reason to be memory mismanagement. Could any one figure out the exact problem?
fwrite throws segmentation fault-untitledjpg
# 2  
Old 08-25-2005
Maybe some of those ptrs point to illegal memories ...
try writing with open/write/close only and see if sigsev occur again on writing data, if so, some ptrs may be erronous Smilie
# 3  
Old 08-25-2005
Are you looping anywhere? Any segmentation faults I have faced were mainly due to accidental infinite loops.
# 4  
Old 08-26-2005
Quote:
Originally Posted by andryk
Maybe some of those ptrs point to illegal memories ...
try writing with open/write/close only and see if sigsev occur again on writing data, if so, some ptrs may be erronous Smilie
Those pointers are valid. I attempted to call fwrite with a hardcoded string. It too crashed.
If u see the attachemnt (in my prev message), the seg. fault has occured in calloc, which is being called by fwrite. So i suspect memory leak/corruption.

You got any idea abt the impact of memory issues on fwrite function?
# 5  
Old 08-26-2005
Quote:
Originally Posted by blowtorch
Are you looping anywhere? Any segmentation faults I have faced were mainly due to accidental infinite loops.

No... there are no infinite loops.
# 6  
Old 08-26-2005
It means memory allocated to the
Code:
pCurSectData->pucData

object is less than
Code:
sizeof (Uchar_t) * pCurSectData->ulDataSize

# 7  
Old 09-13-2005
The above problem has been solved. Actually memory overrun was happening in a memcpy operation. This memory overrun caused the fwrite call to crash.

I detected that culprit memcpy code by placing fwrite randomly through the program flow. Then i picked up the first fail of fwrite function. After correcting the memory overrun in the memcpy call, the program proceeds smoothly.

Thanks all.
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