C++ – Disable GCC “may be used uninitialized” on a particular variable

ccompiler-warningsgcc

I'm getting this warning on a stack variable:

warning: object.member may be used uninitialized in this function

In this case I do not wish to force initialization to just to get rid of the warning as it consumes CPU cycles. The variable is a POD structure so a memset on it is not zero cost. I can verify that the variable is never used uninitialized, so I'd just like to suppress the warning for it.

In general I do want the warning, just not on this particular variable in this particular scenario. How can I suppress the warning?

Looks like the pragma diagnostics are the correct way to go but they require quite a recent version of GCC (4.6)

No acceptable solution prior that version is known.

Best Answer

Try doing this:

 #pragma GCC diagnostic ignored "-Wuninitialized"
        foo(b);         /* no diagnostic for this one */

This pragma comes in three interesting and helpful flavors : warning, error, ignored. See 6.56.10 Diagnostic Pragmas for their usages. The link says,

GCC allows the user to selectively enable or disable certain types of diagnostics, and change the kind of the diagnostic. For example, a project's policy might require that all sources compile with -Werror but certain files might have exceptions allowing specific types of warnings. Or, a project might selectively enable diagnostics and treat them as errors depending on which preprocessor macros are defined.

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