Messages in this thread | | | Subject | Re: [PATCH] Re: 2.5.3-pre1 compile error | From | Russ Allbery <> | Date | Tue, 15 Jan 2002 20:59:32 -0800 |
| |
dmeyer <dmeyer@dmeyer.net> writes: > In article <20020116015513.L32088@suse.de> you write:
>> I'm sure I read somewhere that gcc is clever enough to know when it >> hits a #include, it checks for a symbol equal to a mangled version of >> the filename before including it. (Ie, doing this transparently).
>> Then again, I may have imagined it all.
No, you read that gcc notices when the entirety of a source file is wrapped in an #ifdef guard and won't re-read that file when it's included again if the symbol is defined.
> In answer to Linus' question...yes, in a large system redundent include > guards can make a real difference, particularly for headers which get > included by other headers regularly.
Yes, but you don't need to put them around the #include. Just make sure there is nothing but comments outside the multiple inclusion guards in the header files and any competent compiler will do the right thing.
-- Russ Allbery (rra@stanford.edu) <http://www.eyrie.org/~eagle/> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |