Date: Mon, 17 Feb 2014 08:55:59 -0500 From: Julio Merino <jmmv@outlook.com> To: Garrett Cooper <yanegomi@gmail.com> Cc: freebsd-testing@FreeBSD.org, David Chisnall <theraven@FreeBSD.org>, Dimitry Andric <dim@FreeBSD.org> Subject: Re: Compile error with gcc Message-ID: <BLU0-SMTP3338CC4EB901473B7FC4A23C0990@phx.gbl> In-Reply-To: <2281FB5D-2BF0-4763-AC24-67EC3864D39B@gmail.com> References: <695E42A3-2009-4DD7-B10E-BF8465C89D39@gmail.com> <A8EF2DCC-5F11-4405-88D1-05A193AB7BAF@gmail.com> <D10C2EBB-36EC-4292-A944-4356EA5657F2@FreeBSD.org> <BLU0-SMTP284F6428835416F4D9E3727C09E0@phx.gbl> <849648F5-7834-45DD-8BDF-6385BF4F82DB@FreeBSD.org> <BLU0-SMTP35FABDADF1BB4D66F59E02C09E0@phx.gbl> <2281FB5D-2BF0-4763-AC24-67EC3864D39B@gmail.com>
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On Feb 17, 2014, at 01:07 , Garrett Cooper <yanegomi@gmail.com> wrote: >=20 > Thanks Dimitry for the input. >=20 > Should this check be done with=85 >=20 > #if defined(__cplusplus) && __cplusplus >=3D <some-date> I'm not sure it's going to work. I think Dimitry mentioned that our = libstdc++ should already provide std::vsnprintf, but due to the flags = it's built with, it doesn't. I'm not sure if, due to this, the version = check above would do the right thing. > etc, and if so, what c++ standard was vsnprintf incorporated into? It = looks like <some-date> should be 201103L (c++11) = (http://en.cppreference.com/w/cpp/io/c/vfprintf ). If so, then the = configure.ac tests should instead set the appropriate -std variable (or = setting), then test for c++=92s existence. The point of tests in configure.ac scripts is to _not_ do the above = style of checks. If you are going to use those, then you don't need = configure because you can stick those into the code: configure should be = checking what the compiler actually does, not what it claims to support. = This way the checks are future-proof and are going to work even for = compilers you have not tried yet. Note that the check in configure.ac is working just fine and that's not = the problem. The problem is in FreeBSD, where we have a single = bconfig.h for the two compilers and the two compilers behave differently = in at least one of the detected settings. So... we could generate two bconfig.h files, one for each compiler, and = use them accordingly... or we could try to eliminate the divergence = altogether. To do the latter, I think it's enough to remove the = conditional and leave the code doing: namespace std { using ::vsnprintf; } in all cases. It works in clang but I don't know what the standard has = to say in this regard! (FYI: I fixed the immediate problem in HEAD by changing bconfig.h to = #undef the setting -- just as we had been doing since the initial import = of ATF.)=
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