Fix crash due to non-contiguous EMACS_INT (Bug#10780).

[bpt/emacs.git] / src / ChangeLog

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+2012-02-20  Paul Eggert  <eggert@cs.ucla.edu>
+
+       Fix crash due to non-contiguous EMACS_INT (Bug#10780).
+       * lisp.h (VALBITS): Move definition up, so that USE_LSB_TAG can use it.
+       (USE_LSB_TAG): Do not define if UINTPTR_MAX >> VALBITS == 0.
+       It's useless in that case, and it can cause problems on hosts
+       that allocate halves of EMACS_INT values separately.
+       Reported by Dan Horák.  Diagnosed by Andreas Schwab in
+       <http://debbugs.gnu.org/cgi/bugreport.cgi?bug=10780#30>.
+       * mem-limits.h (EXCEEDS_LISP_PTR): Define to 0 on hosts where
+       UINTPTR_MAX >> VALBITS == 0.  This is required by the above change;
+       it avoids undefined behavior on hosts where shifting right by more
+       than the word width has undefined behavior.
+
 2012-02-19  Chong Yidong  <cyd@gnu.org>
 
        * fileio.c (Ffile_name_directory, Ffile_name_nondirectory)