Simplify STRING_AT macro.

Protect Tcl_GetIndexFromObjStruct from invalid "offset" values, like 0 or -1. Undocumented, because I don't want to promote people start using that.

1 files changed, 9 insertions, 5 deletions

diff --git a/generic/tclIndexObj.c b/generic/tclIndexObj.c
index 944fb8e..8ec1b68 100644
--- a/generic/tclIndexObj.c
+++ b/generic/tclIndexObj.c
@@ -53,12 +53,12 @@ typedef struct {
  * The following macros greatly simplify moving through a table...
  */
 
-#define STRING_AT(table, offset, index) \
-	(*((const char *const *)(((char *)(table)) + ((offset) * (index)))))
+#define STRING_AT(table, offset) \
+	(*((const char *const *)(((char *)(table)) + (offset))))
 #define NEXT_ENTRY(table, offset) \
-	(&(STRING_AT(table, offset, 1)))
+	(&(STRING_AT(table, offset)))
 #define EXPAND_OF(indexRep) \
-	STRING_AT((indexRep)->tablePtr, (indexRep)->offset, (indexRep)->index)
+	STRING_AT((indexRep)->tablePtr, (indexRep)->offset*(indexRep)->index)
 
 /*
  *----------------------------------------------------------------------
@@ -138,7 +138,7 @@ Tcl_GetIndexFromObj(
  *	proper match, then TCL_ERROR is returned and an error message is left
  *	in interp's result (unless interp is NULL). The msg argument is used
  *	in the error message; for example, if msg has the value "option" then
- *	the error message will say something flag 'bad option "foo": must be
+ *	the error message will say something like 'bad option "foo": must be
  *	...'
  *
  * Side effects:
@@ -170,6 +170,10 @@ Tcl_GetIndexFromObjStruct(
     Tcl_Obj *resultPtr;
     IndexRep *indexRep;
 
+    /* Protect against invalid values, like -1 or 0. */
+    if (offset < (int)sizeof(char *)) {
+	offset = (int)sizeof(char *);
+    }
     /*
      * See if there is a valid cached result from a previous lookup.
      */