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From: "eggert at cs dot ucla.edu" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug preprocessor/98021] #warning issues redundant diagnostic lines
Date: Sat, 28 Nov 2020 01:30:34 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98021

--- Comment #7 from eggert at cs dot ucla.edu ---
(In reply to Andreas Schwab from comment #5 and #6)
> There can be comments....
> Also, the source may come from a different place than the directive.

For the unusual case where the #warning line invokes preprocessor macros
defined elsewhere, it would be OK to output the warning both before and aft=
er
preprocessing (to help with debugging the warning machinery, presumably).
(Comments might cause something similar, I suppose, though that's less
important.)

However, for the case that I mentioned where the #warning line just contain=
s a
string, the duplicate messages are confusing and redundant, and the duplica=
tion
should be avoided in this more-typical case.=