Re: [PATCH 64bit] ssize_t

[Ralf Corsepius <ralf dot corsepius at rtems dot org>]

On 02/20/2013 04:17 PM, Corinna Vinschen wrote:
> On Feb 20 16:08, Ralf Corsepius wrote:
> > On 02/20/2013 03:14 PM, Corinna Vinschen wrote:
> > > Hi Yaakov,
> > >
> > > On Feb 20 03:23, Yaakov (Cygwin/X) wrote:
> > > > I just discovered an issue resulting from this commit:
> > > >
> > > > 2002-06-27  Jeff Johnston  <jjohnstn@...>
> > > >
> > > >          * libc/include/sys/_types.h: Define _ssize_t as int if int is
> > > >          32-bits, otherwise define it as long.
> > > >
> > > > On x86_64-cygwin (as on Linux), int is still 32 bits, but size_t is a
> > > > 64bit unsigned long and ssize_t should be as large but signed.
> > > > Possible patch for newlib attached; corresponding patches for
> > > > cygwin-64bit-branch on cygwin-patches@.
> > >
> > > Thanks for the patch.  I'm just wondering if ssize_t shouldn't ideally
> > > be based on size_t, at least when using GCC.  GCC has a predefined
> > > __SIZEOF_SIZE_T__ macro.
> > >
> > > What I'm thinking of is something like
> > >
> > > #ifndef __ssize_t_defined
> > > # ifdef __SIZEOF_SIZE_T__
> > > #  if defined (__SIZEOF_INT__) && __SIZEOF_SIZE_T__ == __SIZEOF_INT__
> > > typedef int ssize_t;
> > > #  else
> > > typedef long ssize_t
> > > #  endif
> > > # elif defined(__INT_MAX__) && defined(__LONG_MAX__) && __LONG_MAX__ == __INT_MAX__
> > > typedef int _ssize_t;
> > > # else
> > > typedef long _ssize_t;
> > > # endif
> > > #endif
> > >
> > >
> > > Does that make sense?
> >
> > GCC requires exact symmetry of types between ssize_t and size_t.
> > I.e. checking for sizes of types is not sufficient for [s]size_t.
>
> Do you have a code suggestion then?

Unfortunately no.

So far, the best I have been able to come up with for RTEMS, was a 
pretty unpleasant, error prone and lacking generality preprocessor cascade:

ATM, it looks like this:
<snip>
+++ newlib-1.20.0/newlib/libc/sys/rtems/machine/_types.h 
2012-10-15 10:31:19.635621334 +0200
@@ -13,7 +13,7 @@
  * could be applied here.
  */

-#if defined(__i386__) || defined(__m32r__) || defined(__h8300__) || 
defined(__arm__) || defined(__bfin__) || defined(__m68k__)
+#if defined(__i386__) || defined(__m32r__) || defined(__h8300__) || 
(defined(__arm__) && !defined(__ARM_EABI__)) || defined(__bfin__) || define
 #if defined(__H8300__)
 typedef signed int _ssize_t;
 #else
@@ -23,7 +23,8 @@
 #elif defined(__sparc__) && defined(__LP64__)
 typedef long signed int _ssize_t;
 #define __ssize_t_defined 1
-#elif defined(__AVR__) || defined(__lm32__) || defined(__m32c__) || 
defined(__mips__) || defined(__moxie__) || defined(__PPC__) || defined(__sp
+#elif defined(__AVR__) || defined(__lm32__) || defined(__m32c__) || 
defined(__mips__) || defined(__moxie__) || defined(__PPC__) || defined(__sp
+  || defined(__v850__) || defined(__v851__)
 typedef signed int _ssize_t;
 #define __ssize_t_defined 1
 #else
</snip>

>  GCC doesn't define ssize_t
> by itself,
Right, but GCC (IIRC, since 4.4) defines size_t (__SIZE_T_TYPE__) and 
also comes with pretty aggressive fprintf-format strings checks related 
to [s]size_t.

That said, IMO, in an ideal world, GCC also would define a corresponding 
__SSIZE_T_TYPE__.

Ralf