Thread: double free or corruption (out)

Hey guys I got an assignment due tomorrow of multiplying two matrices. I got everything done but when I free the second matrix then I get this error:

Code:

*** glibc detected *** ./a.out: double free or corruption (out): 0x0000000001f5e2f0 ***
======= Backtrace: =========
/lib/libc.so.6[0x7fa69d033a58]
/lib/libc.so.6(cfree+0x76)[0x7fa69d0360a6]
./a.out[0x400aad]
/lib/libc.so.6(__libc_start_main+0xe6)[0x7fa69cfd8466]
./a.out[0x400659]
======= Memory map: ========
00400000-00401000 r-xp 00000000 08:05 3498047                            /home/craig/Desktop/Cis308/a.out
00601000-00602000 r--p 00001000 08:05 3498047                            /home/craig/Desktop/Cis308/a.out
00602000-00603000 rw-p 00002000 08:05 3498047                            /home/craig/Desktop/Cis308/a.out
01f5e000-01f7f000 rw-p 01f5e000 00:00 0                                  [heap]
7fa698000000-7fa698021000 rw-p 7fa698000000 00:00 0 
7fa698021000-7fa69c000000 ---p 7fa698021000 00:00 0 
7fa69cda2000-7fa69cdb8000 r-xp 00000000 08:05 647270                     /lib/libgcc_s.so.1
7fa69cdb8000-7fa69cfb8000 ---p 00016000 08:05 647270                     /lib/libgcc_s.so.1
7fa69cfb8000-7fa69cfb9000 r--p 00016000 08:05 647270                     /lib/libgcc_s.so.1
7fa69cfb9000-7fa69cfba000 rw-p 00017000 08:05 647270                     /lib/libgcc_s.so.1
7fa69cfba000-7fa69d123000 r-xp 00000000 08:05 647470                     /lib/libc-2.8.90.so
7fa69d123000-7fa69d322000 ---p 00169000 08:05 647470                     /lib/libc-2.8.90.so
7fa69d322000-7fa69d326000 r--p 00168000 08:05 647470                     /lib/libc-2.8.90.so
7fa69d326000-7fa69d327000 rw-p 0016c000 08:05 647470                     /lib/libc-2.8.90.so
7fa69d327000-7fa69d32c000 rw-p 7fa69d327000 00:00 0 
7fa69d32c000-7fa69d34b000 r-xp 00000000 08:05 647467                     /lib/ld-2.8.90.so
7fa69d533000-7fa69d535000 rw-p 7fa69d533000 00:00 0 
7fa69d545000-7fa69d54a000 rw-p 7fa69d545000 00:00 0 
7fa69d54a000-7fa69d54b000 r--p 0001e000 08:05 647467                     /lib/ld-2.8.90.so
7fa69d54b000-7fa69d54c000 rw-p 0001f000 08:05 647467                     /lib/ld-2.8.90.so
7fffa5537000-7fffa554c000 rw-p 7ffffffea000 00:00 0                      [stack]
7fffa55ff000-7fffa5600000 r-xp 7fffa55ff000 00:00 0                      [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
Aborted

Here is my code:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define Mult(x, y) (x)*(y)


typedef struct matrix
{
	int r;
	int c;
	int **mtx;
}matrix;

matrix m1;
matrix m2;
void MultiplyMatrices();

int main(int argc,char * argv[])
{
	FILE *input = fopen(argv[1], "r");
	if (input==NULL)
	{
		printf("Error Opening File.\n");
		return 0;
	}
	int rows;
	int cols;
	fscanf(input, "%d %d" , &rows, &cols);
	
	//read in matrix 1
	m1.r = rows;
	m1.c = cols;
	m1.mtx= malloc(m1.r*sizeof(int));
	int i;
	for(i=0; i<m1.r; i++)
	{
		m1.mtx[i] = malloc(m1.c*sizeof(int));
	}
	int j;
	for(i=0; i<m1.r; i++)
	{
		for(j=0; j<m1.c; j++)
		{
			fscanf(input, "%d " , m1.mtx[i]+j);
		}
	}
	//print matrix 1
	printf("The first matrix is: \n");
	for(i=0; i<m1.r; i++)
	{
		for(j=0; j<m1.c; j++)
		{
			printf("	%d ", m1.mtx[i][j]);
		}
		printf("\n");
	}

	//read in matrix 2
	fscanf(input, "%d %d" , &rows, &cols);
	m2.r = rows;
	m2.c = cols;
	m2.mtx= malloc(m2.r*sizeof(int));
	for(i=0; i<m2.r; i++)
	{
		m2.mtx[i] = malloc(m2.c*sizeof(int));
	}
	for(i=0; i<m2.r; i++)
	{
		for(j=0; j<m2.c; j++)
		{
			fscanf(input, "%d " , m2.mtx[i]+j);
		}
	}
	//print matrix 2
	printf("The second matrix is: \n");
	for(i=0; i<m2.r; i++)
	{
		for(j=0; j<m2.c; j++)
		{
			printf("	%d ", m2.mtx[i][j]);
		}
		printf("\n");
	}

	MultiplyMatrices();


	//free memory
	for(i=0;i<m1.r;i++)
	{
		free(m1.mtx[i]);
	}
	free(m1.mtx);
	//I think these should be here, but it says I double deleted them.
	for(i=0; i<m2.r;i++)
	{
		free(m2.mtx[i]);
	}
	free(m2.mtx);
	fclose(input);
}

^^ the two bold and underlined lines are the ones that cause the error.

I took out MultiplyMatrices function as it didn't change anything. Thanks for any help,

Craig.

If I comment out the matrix multiply, I get printed matrices without any seeming fuss or muss or complaints from libc. Perhaps it is in your MultiplyMatrices?

Weird, It gave me that error before I implemented the multiplication. I commented it out and even cut it out and I still get the error. I'm pretty new to c, I'm not real sure what to do. I swear I've looked over this code 1000 times and m1 and m2 are identical, but only m2 gives me the error.

Thanks for the replies.

Thanks vart, that worked. I remember doing that in lab now that you mention it. I appreciate everyones help.