g++ comparison between pointers and integers

Posted on 2000-02-28
Medium Priority
Last Modified: 2010-04-22
I have existing code that I'm trying to port to Linux and it's becoming a real pain that g++ doesn't allow comparison between pointers and integers.  The specific problem I keep running into is using NULL to be integer value 0.  For example, the following code won't compile

int get_int(){ ... }

int main(){
  if(get_int() == NULL) ...

because it says that ANSI C++ forbids comparison between pointers and integers.  The -traditional flag does the trick if compiling C code, but doesn't work with C++ code.

The code compiles fine using the compilers on NT, AIX, and Solaris.

Is there a way to get g++ to allow this?

Question by:relleh
  • 2
LVL 40

Accepted Solution

jlevie earned 150 total points
ID: 2565949
Make the test like:

if(get_int() == (int)NULL)

NULL is defined to be null pointer and get_int() is of type int.

Author Comment

ID: 2566452
I was hoping g++ had a command line option that told it to allow the comparison.  The problem is that there are too many places in the code where that sort of thing is done.  I could also make the test be

if(get_int() == 0)

and completely get rid of NULL, but that takes a lot of time digging through all the code.  Also, because the other programmers already have the habit of using NULL that way, when new code is added it's likely to show up again.

LVL 40

Expert Comment

ID: 2566525
Well, yeah, it's a pain to fix and you have to keep beating people over the head to get them to do things the right way, but there's no guarantee that the next release of Sun's C++ (or somebody else's) won't take the same view that g++ does.

<personal rant mode on> If the code violates the standard, it ought to be changed, period. I've spent entirely too many hours fixing non-compliant codes that worked by a fluke on one platform/compiler/version and failed miserably on another. <personal rant mode off>.

Expert Comment

ID: 2570248
I'd suggest you change all NULL's to 0's. Remember, this does NOT have to be done by hand !!! you can use sed, or your favorite tool to do that !!!

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