Re: [Tinycc-devel] [FreeBSD support] __aligned(n) + __pure issues

[Michael Matz]

Hi,

On Sat, 15 Oct 2016, grischka wrote:

> Christian Jullien wrote:
> > Ok,
> > The point is that it compiles ROOTB but then a single line program using 
> > only ISO include and std C library fails because of __aligned in a 
> > **system** header.
> > I agree that __aligned is a probably a macro or a gcc FreeBSD specific 
> > extension, but no one wants to change it source file (or Makefile) when he 
> > the switch from gcc to tcc
> > To be more clear, let me start again from scratch (Don’t miss *Linux* in 
> > banner with -v and -vv)
>
> Please!  You were clear.  Anyway, maybe this helps:
>   
> http://repo.or.cz/tinycc.git/commitdiff/f3c1ea6c2d7dca7883985820e46ec536e2d7e8cc
> It is expected that this could break system xyz whatever.

Ugh.  TCC doesn't support enough of GNU C to be able to sensibly 
define __GNUC__.  I've privately started to support more of it, but it's 
nowhere complete.  I don't think that's going to work very well.

Christian: you were completely clear in your initial mail.  I was trying 
to make you look into FreeBSDs headers to find out _where_ the __aligned 
macro is defined, under which conditions.  I wanted to know this so that I 
can suggest an acceptable and least intrusive way for TCC to work around 
the problem in FreeBSDs standard headers.

> Some background research:
>
> - obviously FreeBSD headers expect __GNUC__
>  http://pcc.ludd.ltu.se/jira/browse/PCC-18

Meeh.

> - patch for sys/cdefs.h suggested by PCC
>  http://pcc.ludd.ltu.se/ftp/pub/patches/openbsd-include-sys-081220.diff
>
> - __GNUC__ nowadays seems to mean the C dialect rather than the compiler
>  https://gcc.gnu.org/ml/gcc/2008-07/msg00026.html
>
> Not sure whether we really want to define __GNUC__.  This might
> cause all kind of problems.  However if we don't then sys/cdefs.h does
>    #define __attribute__(xyz)

So, FreeBSDs problem really.  Well, we could add work arounds in TCC of 
course, and possibly defining __GNUC__ is the most sensible work around. 
But please, then only for the BSDs, not for all the rest.  The other 
possibility is to define __aligned ourself (also only on *BSD), if that's 
the only missing thing breaking otherwise standard-conforming programs on 
FreeBSD.  The compat define should come from some header IMHO, e.g. 
stddef.h, not pre-defined by TCC itself.


Ciao,
Michael.