[Issue 21177] printf check does not recognize GNU extensions

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21177

--- Comment #3 from Mathias LANG <pro.mathias.lang at gmail.com> ---
A new feature is triggering deprecation messages in perfectly working code.
Yes, it is a regression, as all false-positives are.

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