Thread: VERY strange problem. My program hangs unless I add a test variable and never use it.

the input of the function is a binary number, for example "10110" is the one being passed as i test this. The function is supposed to convert it to a hexadecimal. anyway, it's not finished, but this one thing is infuriatingly holding me up.

for some reason a simple malloc statement is making my program hang. but when i tried to make another variable and malloc it, everything worked fine. It also is noteworthy that WHERE i put this test = malloc(5) matters, in some places it works, and in others the program hangs.

I have no idea what's going on :[

Code:

char * bin2Hex(char *binary){
    char *paddedBin, *hexValue, *temp, *test;
    int pad, strLength, i, j, hexLength;

    strLength = strlen(binary);

    while (strLength % 4 != 0)
        strLength++;

    pad = strLength - strlen(binary);
    paddedBin = malloc(strLength);

    for(i = 0; i < strLength; i++)
        paddedBin[i] = '\0';

    for(i = 0; i < pad; i++)
        paddedBin[i] = '0';

    printf("test 1");
    test = malloc(5);      ///IF I REMOVE THIS LINE THE PROGRAM HANGS 
    printf("test 2");
    strcat(paddedBin, binary);
    printf("test 3");

    hexLength = strLength/4;
    hexValue = malloc(hexLength);   //PROGRAM HANGS HERE IF I REMOVE test = malloc(5);

    for(i = 0; i < hexLength; i++){
        temp = malloc(4);
        for(j = 0; j < 4; j++)
            temp[i] = '\0';

        strncat(temp, paddedBin+(4*i), 4);
        printf("temp: %s\n", temp);
    }

    return NULL;
}

paddedBin does not have enough space allocated to it for

Code:

strcat(paddedBin, binary);

to succeed. Even with no padding, it would require strLength+1 just to hold binary itself, and the padding added only makes it worse.

jesus christ. i hate myself.

thanks so much.