Date: Tue, 21 Feb 2023 11:09:14 -0800 From: Fangrui Song <i@...kray.me> To: musl@...ts.openwall.com Subject: Re: [PATCH] Use __builtin_FILE/__builtin_LINE if available On Sat, Feb 18, 2023 at 4:17 AM Jon Chesterfield <jonathanchesterfield@...il.com> wrote: > > On Sat, 18 Feb 2023, 02:54 Fangrui Song, <i@...kray.me> wrote: > > On Fri, Feb 17, 2023 at 6:03 PM Rich Felker <dalias@...c.org> wrote: > > > > On Fri, Feb 17, 2023 at 05:33:33PM -0800, Fangrui Song wrote: > > > C++ inline functions are requred to have exact same sequence of tokens > > > in every translation unit, but __FILE__ and __LINE__ may expand to > > > different tokens. The ODR violatioin is usually benign, but it can lead > > > to errors when C++20 modules are used. > > > > It is sad that C++ modules broke 'assert' but not surprising. Modules were largely created out of aversion to macros. This isn't something libc can fix though, I suggest a defect report against C++ instead. > > Changing the semantics of assert in C seems like a bad thing to do. > > Thanks I disagree. This is a footgun where the right fix (or workaround, if you prefer) is on the libc side. It is fairly reasonable for a header to use assert and not expect two includes using different paths to not cause C++ module problems. The current module behavior regarding macros is a reasonable compromise. It can be evolved (e.g. https://gracicot.github.io/modules/2018/05/14/modules-macro.html).
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