On Aug 2 13:36, Sebastian Huber wrote:
> Hello,
>
> we have via <stdio.h>
>
> #define getchar() getc(stdin)
> #define putchar(x) putc(x, stdout)
>
> which is
>
> #ifndef __CYGWIN__
> #ifndef lint
> #define getc(fp) __sgetc_r(_REENT, fp)
> #define putc(x, fp) __sputc_r(_REENT, x, fp)
> #endif /* lint */
> #endif /* __CYGWIN__ */
> #endif /* __cplusplus */
>
> which is mostly
>
> #define __sgetc_r(__ptr, __p) __sgetc_raw_r(__ptr, __p)
>
> #define __sputc_r(__ptr, __c, __p) __sputc_raw_r(__ptr, __c, __p)
>
> which is
>
> /*
> * The __sfoo macros are here so that we can
> * define function versions in the C library.
> */
> #define __sgetc_raw_r(__ptr, __f) (--(__f)->_r < 0 ? __srget_r(__ptr,
> __f) : (int)(*(__f)->_p++))
>
> _ELIDABLE_INLINE int __sputc_r(struct _reent *_ptr, int _c, FILE *_p) {
> #ifdef __SCLE
> if ((_p->_flags & __SCLE) && _c == '\n')
> __sputc_r (_ptr, '\r', _p);
> #endif
> if (--_p->_w >= 0 || (_p->_w >= _p->_lbfsize && (char)_c != '\n'))
> return (*_p->_p++ = _c);
> else
> return (__swbuf_r(_ptr, _c, _p));
> }
>
> which modifies FILE members without protection of the FILE lock!
> [...]
> What is the purpose of these macros?
If you search for them in newlib, you'll notice that the macros are used
from a couple of places in libc/stdio.
The fact that they are directly called on non-Cygwin platforms is probably
historical, as usual. They are reentrant. As such, and under the
assumption that we're on embedded platforms without preemptive
multi-tasking, the macros work nicely and are faster than the function
calls.
I can think of four ways to solve this:
1. Just add RTEMS to the exceptions, same as Cygwin.
2. Replace
#define getc(fp) __sgetc_r(_REENT, fp)
#define putc(x, fp) __sputc_r(_REENT, x, fp)
with
#define getc_unlocked(fp) __sgetc_r(_REENT, fp)
#define putc_unlocked(x, fp) __sputc_r(_REENT, x, fp)
and let getc/putc simply call the functions.
3. Add a newlib setting to sys/config.h and use that in stdio.h, rather
than excluding targets explicitely. Best is probably an opt-in
config.
4. Move the macros to libc/stdio/local.h and don't use them from
user space at all. This may be a bit harsh on some embedded
targets, but actually I don't know. Most targets have space
constraints and a function would be more prudent then, I guess.
Corinna
--
Corinna Vinschen
Cygwin Maintainer
Red Hat
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: not available
URL: <http://sourceware.org/pipermail/newlib/attachments/20170802/50766d2e/attachment.sig>