Messages in this thread | | | Date | Tue, 25 Apr 2006 10:20:24 +0300 | From | Avi Kivity <> | Subject | Re: Compiling C++ modules |
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Alan Cox wrote: > On Maw, 2006-04-25 at 00:03 +0300, Avi Kivity wrote: > >> Alan Cox wrote: >> I think it's easy to show that the equivalent C++ code would be shorter, >> faster, and safer. >> > > Mathematically the answer is "no you couldn't". You might be able to > argue that a fortran implementation would be faster but not a C++ one. > Maybe not mathematically, but I can try to hand-wave my way through.
By using exceptions, you free the normal return paths from having to check for errors. The exception paths can be kept in a dedicated section, avoiding cache pollution. The total code (and data) size increases, but the non-exception paths size decreases significantly and becomes faster.
Using C++ objects instead of C objects allows you to avoid void pointers, which are difficult for the compiler to optimize due to aliasing. > And for strings C++ strings are suprisingly inefficient and need a lot > of memory allocations, which can fail and are not handled well without C > ++ exceptions and other joyous language features you don't want in a > kernel. C with 'safe' string handling is similar - look at glib. > > We have to make tradeoffs and the kernel tradeoffs have been to keep C > type fast string handling but to provide helpers in the hope people will > actually use them to avoid making mistakes. > You might keep C strings (or something similar) for the vfs paths and use C++ strings for non performance critical code.
-- error compiling committee.c: too many arguments to function
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