Hi, On Mon, Dec 4, 2017 at 2:09 PM, Mathieu Malaterre <mathieu.malaterre@xxxxxxxxx> wrote: > Hi there, > > I've always assumed (before #pragma once), that sentinels were written like: > > https://en.wikipedia.org/wiki/Include_guard#Use_of_.23include_guards > > However grepping the linux source code I see: > > $ cat sound/soc/samsung/pcm.h > #ifndef __S3C_PCM_H > #define __S3C_PCM_H __FILE__ > <...> > #endif /* __S3C_PCM_H */ > > Why would any use: > > #define __S3C_PCM_H __FILE__ > > instead of the simpler: > > #define __S3C_PCM_H > > This is not a copy/paste error, as I can find other references: > > $ grep -r "#define" * | grep "_H " | grep __FILE|wc > 63 189 4996 Nevermind, I understood right after posting. This is to prevent potential conflict in between multiple files being named the same and multiple '__S3C_PCM_H' coming from actual different files. In this case this looks like an error, but I can imagine some file have identical names and thus potential conflicts for sentinels Sorry for the noise, -- Mathieu
