>> 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/