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doc: mention -Wmaybe-uninitialized vs CCP 

CCP interacts poorly with -Wmaybe-uninitialized in some cases by assuming a value
which stops us warning about it (false negatives). Inform users about this
infamous interaction.

gcc/ChangeLog:
	PR tree-optimization/18501

	* doc/invoke.texi (-Wmaybe-uninitialized): Mention interaction with
	CCP.
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Sam James 2025-10-07 01:51:55 +01:00
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@ -8375,7 +8375,10 @@ known to read the object.) Annotating the function with attribute
the object and avoids the warning (@pxref{Common Function Attributes}).
These warnings are only possible in optimizing compilation, because otherwise
GCC does not keep track of the state of variables.
GCC does not keep track of the state of variables. On the other hand,
@option{-Wmaybe-uninitialized} is known not to warn in many situations
(false negatives) due to optimizations taking advantage of undefinedness
of uninitialized uses like constant propagation.
These warnings are made optional because GCC may not be able to determine when
the code is correct in spite of appearing to have an error. Here is one