* lisp.h (TAG_SYMPTR): Don't do arithmetic on NULL.

This is a followup to the "Port Qnil==0 XUNTAG to clang" patch.
Although clang doesn't need it, some other compiler might, and
it's easy enough to be safe.

2 files changed, 7 insertions, 1 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 7a98555cc9c..33030cb8660 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,10 @@
 2015-01-08  Paul Eggert  <eggert@cs.ucla.edu>
 
+        * lisp.h (TAG_SYMPTR): Don't do arithmetic on NULL.
+        This is a followup to the "Port Qnil==0 XUNTAG to clang" patch.
+        Although clang doesn't need it, some other compiler might, and
+        it's easy enough to be safe.
+
         * conf_post.h (ATTRIBUTE_ALLOC_SIZE): Port to clang 3.5.0.
         Apparently clang removed support for the alloc_size attribute.
 
diff --git a/src/lisp.h b/src/lisp.h
index b9263f88c11..97abaade1e1 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -729,7 +729,8 @@ struct Lisp_Symbol
 
 /* Yield an integer that tags PTR as a symbol.  */
 #define TAG_SYMPTR(ptr) \
-  TAG_PTR (Lisp_Symbol, (char *) (ptr) - (char *) (USE_LSB_TAG ? lispsym : 0))
+  TAG_PTR (Lisp_Symbol, \
+           USE_LSB_TAG ? (char *) (ptr) - (char *) lispsym : (intptr_t) (ptr))
 
 /* Declare extern constants for Lisp symbols.  These can be helpful
    when using a debugger like GDB, on older platforms where the debug