steve@maths.warwick.ac.uk (Steve Rumsby) (12/13/89)
Yes, it's possible to make it work. There are two things you need to do,
one to the code itself, and one to the CC script (or to the output of
CC -Fc before feeding to cc itself if you can't hack CC).
1) To the code using stdargs:
First, add this to the beginning, or in a header file that you include,
or somewhere:
#ifdef sparc
#define SA(x) __builtin_va_alist
#else
#define SA(x) x
#endif
Then change code like this:
void
foo(int x, char *p, ...)
{
va_list ap;
if(!p)
return;
va_start(ap, p);
[...etc...]
}
To this:
void
foo(int x, char *SA(p), ...)
{
va_list ap;
if(!SA(p))
return;
va_start(ap, SA(p));
[...etc...]
}
ie. change ALL occurances of the last named argument to SA(name).
2) Changes to CC itself:
Cfront in going to mangle the __builtin_va_alist parameter name, so
we need to unmangle it again so that the C compiler gets to see it.
Do this to the output of cfront:
sed -e 's/__0__builtin_va_alist/__builtin_va_alist/g'
You can either do this in the CC script by changing all occurances of
"cfront" to "cfront | sed", or you can do it to the output of CC -Fc
and feed it to cc manually. This sed script can obviously be generalised
to unmangle a larger set of identifiers (like all __builtin ones) if
necessary (eg. to use gcc instead of cc as the C compiler).
Voila! You now have stdargs working on a sparc machine.
Note that there is a slightly more complex usage of stdargs in C++ which
breaks the above system. This is where arguments after the last named one
have default values, like so:
extern void foo(int, char *, int = 2, ...);
void
foo(int x, char *p, int, ...)
{
va_list ap;
va_start(ap, p);
}
[Is this legal? I found it in ET++]
Cfront will make up names for the unnamed arguments, and the Sun C compiler
complains about arguments after __builtin_va_alist. To make this work you
need to rip out these extra arguments (I don't understand why cfront puts them
there in the first place, actually). This is somewhat more difficult, but
not impossible. I haven't got around to fixing this yet...
Hope all this helps,
Steve.
UUCP: ...!ukc!warwick!steve Internet: steve@maths.warwick.ac.uk
JANET: steve@uk.ac.warwick.maths PHONE: +44 203 523523 x2657prl@iis.UUCP (Peter Lamb) (12/14/89)
If you have source, another approach to the varargs problem on Sun4
(and DS[23]100) is to change the compiler not to add the _aunnn__ that it
tacks onto the variable names IFF they begin with the magic string for
varargs. The following patch will do this for 1.2.1 on Sun4. For
DS[23]100, you will need to change the magic string to "va_alist".
2.0 may be patchable in a similar manner.
Doing this saves having to run yet another pre/postprocessor....
Peter Lamb
uucp: uunet!mcvax!ethz!prl eunet: prl@iis.ethz.ch Tel: +411 256 5241
Integrated Systems Laboratory
ETH-Zentrum, 8092 Zurich
@
@ Recognise the __builtin_ construct for Sun4 systems - used by the
@ varargs.h stuff to tell the compiler that the arguments passed in
@ registers have to be saved on the stack. Needed for the fix in
@ form() in lib/stream/out.c
@
*** print.c_dist Tue Feb 24 16:44:40 1987
--- print.c Mon Oct 16 11:10:42 1989
***************
*** 17,22 ****
--- 17,23 ----
#include "cfront.h"
#include "size.h"
+ extern int strncmp(const char*, const char*, int);
extern FILE* out_file;
char emode = 0;
extern int ntok;
***************
*** 581,587 ****
fprintf(out_file,"_auto__O%d.__C%d_",i,i);
else
// putstring("_auto_");
! fprintf(out_file,"_au%d_",lex_level);
}
break;
case CLASS:
--- 582,595 ----
fprintf(out_file,"_auto__O%d.__C%d_",i,i);
else
// putstring("_auto_");
! // fprintf(out_file,"_au%d_",lex_level);
! // Hack for sun4 varargs;
! // Don't add _au%d if the name starts
! // with "__builtin_". prl 16/10/89
! if(!string
! || strncmp(string, "__builtin_",10))
! fprintf(out_file,
! "_au%d_",lex_level);
}
break;
case CLASS:
--
Peter Lamb
uucp: uunet!mcvax!ethz!prl eunet: prl@iis.ethz.ch Tel: +411 256 5241
Integrated Systems Laboratory
ETH-Zentrum, 8092 Zurich