Re: signal.h conflicting with linux/signal.h (2.4.0)

["Joseph A. Knapka" <jknapka@earthlink.net>]

Guennadi Liakhovetski wrote:
> 
> Hi
> 
> Yesterday I was writing a user-space programme, for which I thought I
> needed (well, eventually I managed without it, but still...) linux/signal.h.
> Then I found out that everything there is hidden from user-space
> programmes by the
> #ifdef __KERNEL__
> instruction. Ok, although I actually needed one of those structs (namely
> struct sigpending), I found a way around it. But, while I tried compiling
> my programme, g++ complained about a conflicting declaration of sigset_t
> in asm/signal.h, #included from linux/signal.h (so, there are some
> declarations exposed to the user space there) and /usr/include/signal.h.
> The latter one was included from some another and another and another
> C++ header... So, is it so, that user-space programmes should not #include
> linux/signal.h nor asm/signal.h (then why isn't sigset_t from asm/signal.h
> hidden by #ifdef __KERNEL__ too?) or what?

Userspace code should never directly #include <[linux|asm]/anything>.
If the userspace headers for the libraries that implement the
relevant functions need to include the kernel headers, they will.
But glibc doesn't do that; the interface between glibc and the
kernel is completely hidden from user code, which is exactly as
it should be. I think older Linux libc4/5 headers included kernel
headers, though.

There are probably exceptions to the rule above, for code that
does very Linux-centric, non-portable tasks that are not supported
by glibc.

Regards,

-- Joe


> Thanks
> Guennadi
> ___
> 
> Dr. Guennadi V. Liakhovetski
> Department of Applied Mathematics
> University of Sheffield, U.K.
> email: G.Liakhovetski@sheffield.ac.uk
> 
> -
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-- Joe Knapka
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