Thread: Serious issue with malloc function

Hi,

I'm facing a critical issue with the malloc function.

Since my implementation is huge, I have copied only a piece of code here which i feel erroneous

Code:

UINT32 nAllocMemSize = 0;

void *utMemAlloc(UINT32 nMemSize)
{
	void *pAllocAddr = NULL;
	
	DEBUG_PRINT(("Start of utMemAlloc\n"));
	
	if(nMemSize != 0)
	{
		nAllocMemSize += nMemSize;
		DEBUG_PRINT(("Allocating Memory of %d bytes. Total Allocated %d\n", nMemSize, nAllocMemSize));
		pAllocAddr = malloc(nMemSize);
		
		if(pAllocAddr == NULL)
		{
			printf("Memory Allocation Failed\n");
		}
	}
	
	DEBUG_PRINT(("End of utMemAlloc\n"));
	return pAllocAddr;
}

Console Output:
===============
(check only the highlighted console output)

Assigning the Address to the Return Variable
End of utCreateInfoListNode

Start of cpLexer_UpdateTokLoc for the token " " of size 1
End of cpLexer_UpdateTokLoc

Start of cpLexer_UpdateTokLoc for the token "*" of size 1
End of cpLexer_UpdateTokLoc
Start of cpLexer_TokenValStore
Start of utMemAlloc
Allocating Memory of 6 bytes. Total Allocated 13681
End of utMemAlloc
End of cpLexer_TokenValStore
Start of cpProcessDecSpec
Start of utCreateInfoListNode
NULL Address. Hence Allocating Memory
Start of utMemAlloc
Allocating Memory of 12 bytes. Total Allocated 13693
End of utMemAlloc

[similiar prints sliced]

Start of utMemAlloc
Allocating Memory of 12 bytes. Total Allocated 13920
End of utMemAlloc
Memory Allocation Success!!!
Assigning the Address to the Return Variable
End of utCreateInfoListNode


Start of cpLexer_UpdateTokLoc for the token " " of size 1
End of cpLexer_UpdateTokLoc


Start of cpLexer_UpdateTokLoc for the token "swblk_t" of size 7
End of cpLexer_UpdateTokLoc
Start of cpLexer_TokenStrValStore
Start of utMemAlloc
Allocating Memory of 8 bytes. Total Allocated 13928
End of utMemAlloc
Start of utMemAlloc
Allocating Memory of 7 bytes. Total Allocated 13935

D:\C_Yacc>

Bug Description:
==================
As you can see, the control exits inbetween without printing the "End of utMemAlloc" at the end of program execution. I was expecting the print statments "Memory Allocation Failed" incase of memalloc failure. But that is also not printed in the console screen. Some times I will get a message box saying "The instruction at "0x7c93426d" referenced memory at "0x000007e8". The memory could not be read". After this my program ends as said above. Could any one please advice me to overcome this issue?

Thanks
Anand V

The bug may be somewhere else. probably you have heap overrun...

Originally Posted by Bayint Naung

The bug may be somewhere else. probably you have heap overrun...

I believe heap memory is not just 13935 (13.6kb)

Also I'm getting the error message some times at 8000 bytes also. This is really confusing for me and i got struck at this point. Request any one to provide inputs on this.

I mean heap overflow?

Code:

char *p = malloc( 10 );
p[12] = 'a';

But in my piece of code am not accessing the memory location i created. I'm sure the program exits when it tries to allocate memory (pAllocAddr = malloc(nMemSize); ) because i can able to see the print statement "Allocating Memory of 7 bytes. Total Allocated 13935" but after which the program ends, which means the last line executed was nothing but pAllocAddr = malloc(nMemSize);

But you use the memory returned from the function rite?
There you may have overwritten the memory you don't belong.
Just isolate the function utMemAlloc() and you'll see the bug is somewhere else.

Using malloc without using free will cause stack overflow.

How is DEBUG_PRINT defined? If it's writing to a buffered stream you may not see its output when it crashes.

As always, for more information one should run in the debugger, preferably with debug code.

I have defined DEBUG_PRINT as follows,

Code:

#define DEBUG_PRINT(PRINT_PARAM) printf PRINT_PARAM

I'm not using free() anywhere in my code. Because i need all the information i created dynamically till my program ends. I'm badly in need of 3 to 5 mb of heap memory for storing all my datas which i parsed from a file. Is there any other way to store the datas in a structured format?

Originally Posted by laserlight

More likely, it will cause a memory leak.

Ah, that's it. Basically, don't use malloc without using free.