[Qemu-devel] Re: [PATCH] scripts: add a guard macro in generated .h files

[Paolo Bonzini]

On 02/21/2011 07:42 AM, Tristan Gingold wrote:
> Mostly a style issue.  It is common to always protect header files
> against multiple inclusion, unless the header is meant to be included
> several times (which is not the case for these config files).  I
> think this is a good practice.

Traditionally, autoconf's config.h headers have no guards either.  This 
can indeed cause some troubles.  However, it also helps highlighting 
poor practices, such as libraries installing a config.h file including 
it from a public header.

> I once got redefinition warnings for macros in config-host.h, but I
> agree that adding the guard macro doesn't fix this issue.

config-host.h should always be the first included header (we are poor at 
this) and its macros should never conflict with anything else.  I think 
we should rather fix the problems you've seen with config-host.h, if you 
can still reproduce them.

Paolo