[PATCH, ARM] Don't use __thumb2__ to select _REENT_SMALL

Jeff Johnston jjohnstn@redhat.com
Tue Jun 2 17:24:00 GMT 2009

Paul Brook wrote:
> On Tuesday 02 June 2009, Paul Brook wrote:
>>> Yes, this leaks out into user code -- at least it does for me.  Try
>>> building the standard arm-eabi multilib tools and then running the gcc
>>> testsuite with -mcpu=cortex-a8 and -mthumb.  Programs such as
>>> gcc.c-torture/exectute/fprintf-1.c will then fail.
>>> The definition of stdout is:
>>> #define stdout  (_REENT->_stdout)
>> In my sources this field lives at the same location in both cases.
> Further investigation indicates upstream newlib is missing the following 
> patch.
> 2009-06-02  Paul Brook  <paul@codesourcery.com>
> 	newlib/
> 	* libc/include/sys/reent.h (_reent): Adjust _REENT_SMALL to be binary
> 	compatible with normal layout
This would require changing the initialization macro in kind or else 
there will be trouble.  I'm not thrilled with leaving two gaps in the 
struct for 16-bit platforms, but there are now 2 unused fields since 
Corinna revamped locale support.  If the unpaired int that is caused by 
the errno move was put below and the unused fields were removed, I could 
certainly live with that as the struct gets smaller and there is one 
left-over int anyway.  Might as well be errno.

That said, I agree with Richard's point.  If the thumb2 flag is not a 
proper check for a platform that requires a small reent struct, then it 
shouldn't be used as such.

Perhaps a staggered approach can be used.  Make the reent change now as 
a stop-gap and work on changing the compiler so that a proper check can 
be made for when reent small should really be used and a proper multilib 
is created.  For now, put a comment in that the thumb2 check is wrong 
and needs to be changed.

Seem reasonable?

-- Jeff J.
> Index: newlib/libc/include/sys/reent.h
> ===================================================================
> --- newlib/libc/include/sys/reent.h	(revision 159552)
> +++ newlib/libc/include/sys/reent.h	(revision 159553)
> @@ -344,14 +344,15 @@ struct _misc_reent
>   * ports with 16-bit int's but 32-bit pointers, align nicely.  */
>  struct _reent
>  {
> +  /* As an exception to the above put _errno first for binary
> +     compatibility with non _REENT_SMALL targets.  */
> +  int _errno;			/* local copy of errno */
>    /* FILE is a big struct and may change over time.  To try to achieve binary
>       compatibility with future versions, put stdin,stdout,stderr here.
>       These are pointers into member __sf defined below.  */
>    __FILE *_stdin, *_stdout, *_stderr;	/* XXX */
> -  int _errno;			/* local copy of errno */
> -
>    int  _inc;			/* used by tmpnam */
>    char *_emergency;

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