llvm dev - Nov 2003 - [LLVMdev] Headers & Libraries

> So what they call "system" headers are basically installed
> headers and user headers are internal ones. In the context of llvm every
> header that is under inlcude is a "system" header (because when
we write an
> install target it will end up in /usr/include/llvm) otherwise it is a user
> header.
We don't want a user to compile a new copy of LLVM using the headers of
a previously-installed version of LLVM.

-- 
gaeke at uiuc.edu

On Friday 14 November 2003 12:45 pm, Brian R. Gaeke
wrote:
> > So what they call "system" headers are basically installed
> > headers and user headers are internal ones. In the context of llvm
every
> > header that is under inlcude is a "system" header (because
when we write
> > an install target it will end up in /usr/include/llvm) otherwise it is
a
> > user header.
>
> We don't want a user to compile a new copy of LLVM using the headers of
> a previously-installed version of LLVM.
including with "" will not accomplish that though any less than
including with
<>. In both cases you will need to specify the correct -I flags to the 
compiler.

-- 

Alkis

On Fri, 2003-11-14 at 10:56, Alkis Evlogimenos wrote:
> On Friday 14 November 2003 12:45 pm, Brian R. Gaeke wrote:
> > > So what they call "system" headers are basically
installed
> > > headers and user headers are internal ones. In the context of
llvm every
> > > header that is under inlcude is a "system" header
(because when we write
> > > an install target it will end up in /usr/include/llvm) otherwise
it is a
> > > user header.
> >
> > We don't want a user to compile a new copy of LLVM using the
headers of
> > a previously-installed version of LLVM.
> 
> including with "" will not accomplish that though any less than
including with
> <>. In both cases you will need to specify the correct -I flags to
the
> compiler.
Let's be clear about something here. There are two cases for #including
LLVM header files. The first case is when compiling LLVM itself. The
second case is when you're using a compiled/installed version of
LLVM.  Life gets simpler when #including for both cases is identical. 

This is what I did in my XPS project. All the source code is in a
directory structure like this:

xps/<module>/Code.h
xps/<module>/Code.cpp

There is no separation of headers and cpp files. When I specify my
makefiles, I indicate which headers are public (installable) and which
are private (not installed).  When I compile XPS, I ALWAYS use:

#include <xps/<module>/Code.h>

The same form of #include is used when compiling something else that
uses XPS because the headers get installed in:

<installdir>/include/xps/<module>/Code.h.

For compiling XPS, all I need is -I$SRCDIR -I$OBJDIR

For using XPS, all I need is -I$INSTALLDIR/include

Note that if you are installing to INSTALLDIR=/usr or /usr/local, then
the single -I$INSTALLDIR/include works for EVERY installed package you
might want to use.

This arrangement has worked well and I'd advise LLVM to follow a similar
pattern to avoid end-user confusion (like mine) down the road.

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