C malloc results

rubadub · 02-09-2008, 03:01 AM

Hi, i'm using the xyssl library to generate some hash's of a file, then there run through this function to convert to hex, before all of them being simultaneously being printed:

Code:

char *funcs_ustr2hex(unsigned char *sum)
{
	int i;
	int len = strlen((char*)sum);
	char *sret="";
	sret = (char *)malloc((len*2)+1);
	//for( i = 0; i < len-1; i++ )
	for( i = 0; i < 16; i++ )
		sprintf( sret, "%s%02x", sret, sum[i] );
	return sret;
}

my output looks like this:

Quote:

md5: ��X5dd39cab1c53c2c77cd352983f9641e1
md2: `�Xb5fcc4d4c05a2c6d25bda588c26663b0
md4: P�Xd4c5dab3ccfcc1d76d58382450f26ed2

I'm assuming it's this function because I don't yet do any conversion along the route (hence still unsigned), and these results look like memory problems.

fantas · 02-09-2008, 07:16 AM

sret is not initialized, i.e. it points to random values after the malloc (which will confuse sprintf).

To put a

Code:

sret[0] = '\0';

before the printing loop will most likely solve this problem.

rubadub · 02-09-2008, 07:40 AM

fan dabby double dozy! rock on tommy... (hope you know the reference! Basically Cheers!)