Jeffrey A Law - Re: -Wuninitialized issues (original) (raw)

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On Tue, 2005-11-01 at 11:06 -0500, Diego Novillo wrote:

On Monday 31 October 2005 18:49, Jeffrey A Law wrote:

Thoughts?

I'm not sure this would buy you much better precision. It's less about better precision as it is about catching those cases which are hidden because of actions of the optimizers without introducing more false positives, unless the user has explicitly asked for them :-)

I was tinkering with PR 18501 a few days ago. It's worth noting that my change will catch 18501 -- without having to twiddle the optimizers in any way shape or form.

Assembling functions: bitmap_print_value_set zz.c: In function 'bitmap_print_value_set': zz.c:7: warning: 'first' may have been used uninitialized in this function, but was later optimized away or proven always initialized

Again, all it's doing is running the "maybe uninitialized" test during the early uninitialized warning pass and comparing the results to the running the "maybe uninitialized" test during the late uninitialized warning pass.

This little table summarizes the possibilities:

Marked Marked Early Late no no -> Variable is always initialized before its uses no yes -> Optimization error, checking failure, abort yes no -> Variable might have been used uninitialized, but those uses were either deleted or some paths through the CFG were unexecutable with the net result being all uses in the optimized code were initialized yes yes -> Variable may be uninitialized before its uses

Jeff

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