[uml-devel] Re: Using compiler.h from uml userspace code (was: Re: uml build error)

[Blaisorblade <blaisorblade@yahoo.it>]

On Wednesday 18 January 2006 22:35, Sam Ravnborg wrote:
> On Wed, Jan 18, 2006 at 01:47:26PM +0100, Blaisorblade wrote:
> > Possible solutions below - akpm doesn't need to read this. Sam, instead,
> > please do read and give an opinion.

> First off. When I see #include 2foo.h" then this tell me that foo is
> found in the same dir as the .c file we are compiling.

Oops... with that "foo.h" I meant the same folder as compiler.h... I'm correct 
or not, with gcc?

> gcc though has a much more weak interpretation of the differences
> between include <foo.h> and #include "foo.h".

> The -I- flag to correct this stupidity is scheduled for removal and when
> I asked on the gcc list no-one bothered to answer so I assume this is
> all done now in 4.x.
> -I- had to purposes, but I cannot recall the other one right now.

1) Stop searching in "."
2) End listing of include search dirs to use only with "" quotes.

(From info gcc -> searching -I-, at least with 3.4).

> From a technical viewpoint nothing is wrong - the only thing being that
> human mortals may be confused when suddenly file are included using a
> different style than usual.

> > With that in, just symlinking include/linux/compiler-*.h into
> > arch/um/include would work well!

> > We prefer to avoid them included as <linux/compiler-*.h> because it could
> > conflict with host headers, unless it's possible to have our headers
> > searched before host ones.

> Thats perfectly doable if we talk kbuild.
> You can just assing to NOSTDINC_FLAGS the directories to search first.

The problem is that those files are building without NOSTDINC_FLAGS, because 
they are the USER_OBJS. Weren't for this they'd simply include 
<linux/compiler.h> and be done. However, I just saw that user supplied 
include directories are searched before system headers.

So, a simpler solution could be involve symlinking just a directory, where to 
put all related files (like linux/byteorder).

> In general I wish all symlinks in the build to hell.
> In many cases they are just repairing a badly thought directory
> structure include/asm being the worst evil of all.
> klibc does the same with no symlinks.

Hmm, how? Btw, I thought that klibc could be very useful for UML (either 
linking to it or taking code to replace glibc one and alter it at will - 
glibc is fairly unreadable for me, hope klibc is clearer).

For instance, since fork() (or actually, clone) + execvp() calls malloc (and 
so kmalloc) from a wrong context, we want to split execvp() into 
search_exec() and execve().

Doing that with glibc code felt horrible...
-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

	

	
		
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