> Yes, and that is exactly my point. The compiler already analyzes the
> logic, and generates the msg if I have a potential problem.
The compiler doesn't analyze the logic as well as you think it does. For
example, there are no warnings here with gcc 4.1.2 using -Wuninitialized
-O:
int foo(int y)
{
int x;
if (y == 1) x = 2;
if (y == 2) return x;
return 0;
}
There are tools that can analyze programs statically, but only the
commercial ones provide what you want, as far as I know.
http://spinroot.com/static/
If you are an IBMer I know of an IBM internal tool that may help.
Also, using gcc 4.1.2, I get the line number of the use, not of the
declaration. Which compiler are you using?
> First, I want to know if I have a potential problem.
This is a very hard problem, especially if your generated code is
many-thousands-of-lines in a single function with gotos. Even worse if
they are backwards gotos.
> I am slowly coming around to the point of view that maybe the dataflow
> analysis is not so hard. The hardest part of such a program is to have
> a correct parser for the input language.
Just write something for gcc and you're all set as far as parsing goes.
Good luck :) In fact, the llvm framework would probably allow you to do
what you wanted, but you may have to write code for it:
http://clang.llvm.org/StaticAnalysis.html
It has a gcc front-end, so parsing isn't an issue.
> In a way, working with the output of the program generator is no different
> than working with someone else's grubby program that gets the used before
> defined msg.
I've never seen a human write a routine so long or complicated that I
couldn't find an uninitialized use of a variable by inspection. I stand by
my assertion that if that's not possible in a reasonable amount of time,
then the code needs re-structuring.
> Someone else says to me, can you help me out? I have 40,000 lines of 30
> programs, and I'm getting this msg 150 times for 150 variables. How do I
> fix it? I mean really fix it, not just make the msg go away.
>
> In that case, I have to assume that I don't have control over how the
> program was written, I just have to fix the problem by finding the stmts
> that may cause errors, and, hopefully only those that may cause errors,
> and exactly which ones.
>
> The script should work for any C++ program, whether it has gotos or not.
If someone came to me with such a proposition I would laugh at them,
unless they paid me a lot of money. If the code is that terrible, there's
a significant risk to making any change at all. The code is just too
fragile.
If you are generating the code that you are concerned about, then you can
just add logic to your generator to ensure that all uses of a generated
variable follow some initialization. Surely if you are generating the uses
and initializations than you have enough information to do the analysis
you have in mind at that point, no?
-Frank
--
----------------------------------
Frank Wallingford
[EMAIL PROTECTED]
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