Question

I’ve been working on a senior project for the last several months now, and a major sticking point in our team’s development process has been dealing wtih rifts between Visual-C++ and gcc. (Yes, I know we all should have had the same development environment.) Things are about finished up at this point, but I ran into a moderate bug just today that had me wondering whether Visual-C++ is easier on newbies (like me) by design.

In one of my headers, there is a function that relies on strtok to chop up a string, do some comparisons and return a string with a similar format. It works a little something like the following:

int main()  
{  
    string a, b, c;  
    //Do stuff with a and b.  
    c = get_string(a,b);  
}   


string get_string(string a, string b)  
{  
    const char * a_ch, b_ch;
    a_ch = strtok(a.c_str(),",");  
    b_ch = strtok(b.c_str(),",");  
}

strtok is infamous for being great at tokenizing, but equally great at destroying the original string to be tokenized. Thus, when I compiled this with gcc and tried to do anything with a or b, I got unexpected behavior, since the separator used was completely removed in the string. Here’s an example in case I’m unclear; if I set a = "Jim,Bob,Mary" and b="Grace,Soo,Hyun", they would be defined as a="JimBobMary" and b="GraceSooHyun" instead of staying the same like I wanted.

However, when I compiled this under Visual C++, I got back the original strings and the program executed fine.

I tried dynamically allocating memory to the strings and copying them the “standard” way, but the only way that worked was using malloc() and free(), which I hear is discouraged in C++. While I’m curious about that, the real question I have is this: Why did the program work when compiled in VC++, but not with gcc?

(This is one of many conflicts that I experienced while trying to make the code cross-platform.)

Thanks in advance!

-Carlos Nunez

Answer 1

Tokens will be automatically replaced by a null-character by function strtok. That is not what you can do with constant data.

To make your code safe and cross-platform consider using boost::tokenizer.