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SubjectRe: [PATCH] Re: 2.5.3-pre1 compile error
dmeyer <> writes:
> In article <> 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 ( <>
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