Re: Problem in Tru64 with autoconf choosen cc flags [PATCH]

[Nicolás Lichtmaier]

> > In Tru64 autoconf likes to select "-std1" as the flag to get an ANSI
> > compiler.
> >    
>
> I think that change was proposed by Kevin Ryde in June
> <http://mail.gnu.org/archive/html/autoconf-patches/2003-06/msg00009.html>
> and was later installed into Autoconf.  The problem is that plain "cc"
> mishandles \x escapes in strings.
>
>  
>
> > The problem is that this is similar to the "-ansi" switch in
> > GCC, and it turns off useful extensions.
> >    
>
> What extensions are these?  Is this documented anywhere?
>
>  
>
> > The normal and recommended switch would be just "-std".
> >    
>
> Besides \x,
> <http://groups.google.com/groups?selm=9ro8ef%2427l6%241%40FreeBSD.csie.NCTU.edu.tw>
> says that Tru64 "cc -std" defines __STDC__ to be 0.  It's clearly more
> conservative to use -std1, but perhaps if -std1 disables some useful
> extensions then we should revisit this issue.
>  
This is an excerpt from the cc(1) manpage:

>  -std
>       Selects the relaxed ANSI language mode. Enforces the ANSI C 
> standard,
>       but allows some common programming practices disallowed by the stan-
>       dard.
>                                                                                  
>  
>       This option does not restrict the Tru64 UNIX name space (for 
> example,
>       the names defined in system header files). To restrict that name 
> space
>       so that only ANSI C reserved names are visible from the ANSI C 
> header
>       files, use the _ANSI_C_SOURCE macro. See standards(5) for more 
> details.
>                                                                                  
>  
>       This option causes the macro __STDC_ to be defined to 0.
>                                                                                  
>  
>   -std0
>       Selects the K & R language mode. This is the default. Enforces 
> the K &
>       R programming style, with certain ANSI extensions in areas where 
> the K
>       & R behavior is undefined or ambiguous. In general, -std0 
> compiles most
>       pre-ANSI C programs and produces expected results. The -std0 option
>       causes the __STDC__ macro to be undefined.
>                                                                                  
>  
>   -std1
>       Selects the strict ANSI language mode. Strictly enforces the ANSI C
>       standard and all its prohibitions (such as those that apply to 
> the han-
>       dling of void types, the definition of lvalues in expressions, 
> the mix-
>       ing of integrals and pointers, and the modification of rvalues).
>                                                                                  
>  
>       This option does not restrict the Tru64 UNIX name space (for 
> example,
>       the names defined in system header files). To restrict that name 
> space
>       so that only ANSI C reserved names are visible from the ANSI C 
> header
>       files, use the _ANSI_C_SOURCE macro. See standards(5) for more 
> details.
>                                                                                  
>  
>       This option causes the macro __STDC_ to be defined to 1. Note 
> that this
>       option also affects linker-defined symbols.  See ld(1) for more 
> infor-
>       mation.
>                                                                                  
>  
>       This option, combined with -O3 or higher, turns on ANSI aliasing 
> rules
>       (-ansi_alias option).


So it seems to me that the retionale for definining __STDC__ to 0 is:
"We allow code which is not strictly ANSI in this mode". This is also
true for the normal gcc mode!

--
Nicolás Lichtmaier.-
Synapsis Argentina
+54(11)4314-3000 (int. 231)