On Wed, Dec 17, 2014 at 7:05 PM, Richard Smith <[email protected]> wrote: > > On Tue, Dec 16, 2014 at 1:17 PM, Nico Weber <[email protected]> wrote: >> >> Ok, I moved -Wkeyword-macro into -pedantic in r224371. I also removed >> -Wreserved-id-macro in the same revision, as it's not covered by the >> standards bit you cited >> > > This seems backwards? > > -Wreserved-id-macro is (was) warning on code that is ill-formed. > -Wkeyword-macro is warning on code that has undefined behavior (only) if a > standard library header is #included. > > C++ [lex.name]p3 (introduced by DR, so applying retroactively to all C++ > standards) says: > > "[S]ome identifiers are reserved for use by C ++ implementations and shall > not be used otherwise; no diagnostic is required. > — Each identifier that contains a double underscore __ or begins with an > underscore followed by an uppercase letter is reserved to the > implementation for any use. > — Each identifier that begins with an underscore is reserved to the > implementation for use as a name in the global namespace." > > Aaron's quote of [macro.names]p2 applies only to "C++ programs that use > the facilities of the C ++ standard library." (per > [constraints.overview]p1), and "If a program declares or defines a name in > a context where it is reserved, other than as explicitly allowed by > this Clause, its behavior is undefined." (per [reserved.names]p1). >
I'm not sure I understand the point here – do you mean the warning should only fire if a standard library has been included? In pedantic mode, I would expect that people would want to know about stuff that's undefined behavior even if they don't happen to include a standard library header at the moment. > In your commit message for r224371 (which hasn't yet hit the mailing > list), you say: > > "-Wreserved-id-macro warns on > > #define __need_size_t > > which is more or less public api for glibc headers." > > I don't agree with your example; these __need_* macros exist only to allow > communication between the /usr/include headers and the compiler-provided > <stddef.h>, because /usr/include needs to include a subset of <stddef.h> > depending on which of its headers is included. They're not for end-users, > and these warnings should be suppressed in system headers. > Some end user code uses them, for example to work around bugs in /usr/include headers. I know of one example in Chromium ( https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/ui/libgtk2ui/gtk2_ui.cc&q=__need_Null&sq=package:chromium&type=cs&l=72 ) and I found https://github.com/asfernandes/firebird/blob/35b06c7892e2440c4f4528b9ecc99969927728e0/src/common/utils.cpp#L35 (there might be more, but github's search is somewhat hard to operate.) Having said that, I'm happy with the warning coming back in an improved form. > That said, there are a bunch of reserved macro names that *is* part of the > glibc public API, such as the _*_SOURCE macro family. If we reinstate this > warning, we should whitelist those ones at least. > > On Mon, Dec 15, 2014 at 10:39 AM, Joerg Sonnenberger < >> [email protected]> wrote: >>> >>> On Mon, Dec 15, 2014 at 10:24:22AM -0800, Nico Weber wrote: >>> > For the "final(a,b,c)" define: should we warn on that? It doesn't >>> change >>> > the meaning of the keyword "final" since that doesn't have parameters. >>> >>> For C++11 and newer: IMO yes. Otherwise, no. >>> >>> Joerg >>> _______________________________________________ >>> cfe-commits mailing list >>> [email protected] >>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits >>> >> >> _______________________________________________ >> cfe-commits mailing list >> [email protected] >> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits >> >>
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