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Port Qnil==0 XUNTAG to clang

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clang has undefined behavior if the program subtracts an integer
from (char *) 0.  Problem reported by YAMAMOTO Mitsuharu in:
http://lists.gnu.org/archive/html/emacs-devel/2015-01/msg00132.html
* lisp.h (lisp_h_XUNTAG) [USE_LSB_TAG]:
(XUNTAG) [!USE_LSB_TAG]: Port to clang 3.5.0.
This commit is contained in:
Paul Eggert 2015-01-07 23:02:01 -08:00
parent 9f654763f2
commit f6a27d26dc
2 changed files with 10 additions and 2 deletions
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7
src/ChangeLog
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@ -1,5 +1,12 @@
2015-01-08 Paul Eggert <eggert@cs.ucla.edu>
Port Qnil==0 XUNTAG to clang
clang has undefined behavior if the program subtracts an integer
from (char *) 0. Problem reported by YAMAMOTO Mitsuharu in:
http://lists.gnu.org/archive/html/emacs-devel/2015-01/msg00132.html
* lisp.h (lisp_h_XUNTAG) [USE_LSB_TAG]:
(XUNTAG) [!USE_LSB_TAG]: Port to clang 3.5.0.
Port GFileMonitor * hack to Qnil==0 platforms
Reported by Glenn Morris in: http://bugs.gnu.org/15880#112
* gfilenotify.c (monitor_to_lisp, lisp_to_monitor): New functions.

5
src/lisp.h
View file

@ -368,7 +368,7 @@ error !;
# define lisp_h_XFASTINT(a) XINT (a)
# define lisp_h_XINT(a) (XLI (a) >> INTTYPEBITS)
# define lisp_h_XTYPE(a) ((enum Lisp_Type) (XLI (a) & ~VALMASK))
# define lisp_h_XUNTAG(a, type) XUNTAGBASE (a, type, 0)
# define lisp_h_XUNTAG(a, type) ((void *) (intptr_t) (XLI (a) - (type)))
# define lisp_h_XUNTAGBASE(a, type, base) \
((void *) ((char *) (base) - (type) + (intptr_t) XLI (a)))
#endif
@ -905,7 +905,8 @@ XUNTAGBASE (Lisp_Object a, int type, void *base)
INLINE void *
XUNTAG (Lisp_Object a, int type)
{
return XUNTAGBASE (a, type, 0);
intptr_t i = USE_LSB_TAG ? XLI (a) - type : XLI (a) & VALMASK;
return (void *) i;
}
#endif /* ! USE_LSB_TAG */