Bug 41804 – Disable MSVC warning 4288

• Component: New Bugs
• Status: RESOLVED FIXED

[Dumitru Daniliuc]

MSVC has a non-standard extension (/Ze /Zc:forScope) that allows variables declared in for-loops to remain in the "outer" scope: http://msdn.microsoft.com/en-us/library/bk5hc10s.aspx. When the same variable is re-declared after the for-loop, the compiler issues warning C4288. There's also a bug in VS2005 that enables this extension even if the /Zc:forScope option wasn't specified: http://connect.microsoft.com/VisualStudio/feedback/details/338010/bogus-compiler-warning-c4288. Looks like we got hit by that bug, so we need to disable that warning.

[Dumitru Daniliuc]

Created attachment 60785 [details]
patch

[Adam Roben (:aroben)]

Comment on attachment 60785 [details]
patch

> +        MSVC has a non-standard extension (/Ze /Zc:forScope-) that allows
> +        variables declared in for-loops to remain visible in the same
> +        scope even after the for-loop
> +        (http://msdn.microsoft.com/en-us/library/bk5hc10s.aspx). When this
> +        extension is enabled, re-declaring the same variable in that scope
> +        results in a C4288 warning.
> +
> +        At the same time, there seems to be a bug in VS2005 that
> +        erroneously enables /Zc:forScope- even when that option is not
> +        specified
> +        (http://connect.microsoft.com/VisualStudio/feedback/details/338010/bogus-compiler-warning-c4288).

This makes it sound like the actual behavior gets enabled, not just the warning. Explaining in the previous paragraph that /Ze turns on the behavior and /Zc:forScope- turns on the warning could clear this up, as could changing the description in this paragraph.

Other than that, r=me

[Dumitru Daniliuc]

(In reply to comment #2)
> (From update of attachment 60785 [details])
> > +        MSVC has a non-standard extension (/Ze /Zc:forScope-) that allows
> > +        variables declared in for-loops to remain visible in the same
> > +        scope even after the for-loop
> > +        (http://msdn.microsoft.com/en-us/library/bk5hc10s.aspx). When this
> > +        extension is enabled, re-declaring the same variable in that scope
> > +        results in a C4288 warning.
> > +
> > +        At the same time, there seems to be a bug in VS2005 that
> > +        erroneously enables /Zc:forScope- even when that option is not
> > +        specified
> > +        (http://connect.microsoft.com/VisualStudio/feedback/details/338010/bogus-compiler-warning-c4288).
> 
> This makes it sound like the actual behavior gets enabled, not just the warning. Explaining in the previous paragraph that /Ze turns on the behavior and /Zc:forScope- turns on the warning could clear this up, as could changing the description in this paragraph.

done. made it more clear that /Ze enables all MSVC extensions and /Zc:forScope- tells the compiler to issue a warning when it sees the same variable declared in a for-loop and then re-declared in the same scope.

[Dumitru Daniliuc]

landed: r62708.