macOS more Kern Protection Failure errors

[farmerdoug]

I read in the right number of bits but get the failure when I try to read them.
My memory has been properly allocated. The code compiles with no errors or warnings.


if ((mfilters[filtnum].filters[j] = (float *)calloc((12 + 3*j) , sizeof(float))) == NULL)
printf("calloc failure\n");
else
num = fread(mfilters[filtnum].filters[j], 1, (12 + 3*j)*sizeof(float), fp);

printf("%d %d \n",j, num);
printf("%f\n", mfilters[0].filters[0][0]);

 

[lee1210]

Without code tags, the example is very hard to read. Without a compilable example it makes it very hard to look at this for you. If you can give more info, we're more likely to be able to help.

-Lee

 

[farmerdoug]

more Kern Protection.

I'm sorry, What is a code tag?

The entire code includes some external libraries. If you are willing to look through the whole code, I'd be glad to send everything to you.
Thanks
Doug

 

[kainjow]

code tag

 

[farmerdoug]

code with tabs.

This code gets the kern protection error

if ((mfilters[filtnum].filters[j] = (float *)calloc((12 + 3*j) , sizeof(float))) == NULL)
printf("calloc failure\n");
else
num = fread(mfilters[filtnum].filters[j], 1, (12 + 3*j)*sizeof(float), fp);

printf("%d %d \n",j, num);
printf("%f\n", mfilters[0].filters[0][0]);

This code prints the wrong number; fprow is not assigned to mfilters[0].fprow

if ( (num = fscanf(map, "%d %d, %d %d\n", &fcol, &frow, &fpcol, &fprow)) == 4)
					{
						if( (col == fcol) && (row == frow ))
						{
						found = TRUE;
						rewind(map);
						mfilters[filtnum].col = col;
						mfilters[filtnum].row = row;
						mfilters[filtnum].fpcol = fpcol;
						mfilters[filtnum].fprow = fprow;
						printf("%d %d \n", fprow, mfilters[0].fprow);
                                          }

 

[SydneyDev]

Does the final printf need a pointer dereference?

printf("%f\n", *(mfilters[0].filters[0][0]));

... or, is the printf already trying to deference it, but it's 0, so it's trying to follow a null pointer? That could cause a protection fault. Whether through the calloc or the loading, there must be a null pointer in the structure.

 

[farmerdoug]

reply

no. Putting in the deference operator results in a compiler error.
The code compiles and does not give me any errors when allocating memory or when trying to write to the structure I only have problems when I try and read the values in the structure.

 

[iSee]

I've got no context here, but shouldn't this line:

printf("%f\n", mfilters[0].filters[0][0]);

be something like this:

printf("%f\n", mfilters[filtnum].filters[j][0]);[/QUOTE]

Is that the line it is crashing on?

Also, double-check that mfilters[filtnum].filters[j] exists and is properly allocated before you assign values to it. For example, perhaps filtnum or j is out-of-bounds.

 

[farmerdoug]

reply

It crashes there and says
Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_PROTECTION_FAILURE at address: 0x00000000

By the time it gets to that line, data should have been read in, as with the failure to print the right value for mfilters[filtnum].fprow

 

[SydneyDev]

at address: 0x00000000

Address 0 - that's a sure sign you're trying to dereference a null pointer.

 

[farmerdoug]

reply

Sure, but why would I be if I'm allocating memory with calloc and not getting any error messages?