Re: gcc4's uninitialized-variable warnings

Tom Lane wrote:
> I asked some gcc experts at Red Hat about the new variable-may-be-used-
> uninitialized warnings that gcc 4.x reports.  These occur in cases
> like
> 
>     int    i, j;
>     ...
>     foo(&i, &j);
>     // use i and j
> 
> I had thought that gcc was being stricter about the possibility that the
> called function might not set its output parameters, but the true story
> is entirely different.  There's been no change in the strictness of the
> check for external function calls.  What is happening is that if foo()
> is static and gcc chooses to inline it into the calling function, you
> will now see a warning if the transformed code fails the check.  In
> essence this means that there is a code path through foo() that doesn't
> set the output parameter.
> 
> Armed with that knowledge, we can fix these warnings by ensuring the
> callee sets the output parameters in all code paths; which is often
> cleaner than having the caller initialize the variables before call,
> as I was afraid we'd have to do.
> 
> I'll work on cleaning these up.

Wow, that is a nifty complier check.

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