string last: fix segfault with invalid index

[string last foo bar -1] gave segfault due to missing check for invalid index. Fixes #161 Signed-off-by: Steve Bennett <steveb@workware.net.au>
msteveb · Jul 11, 2020 · da293a1 · da293a1
1 parent 4e2cdac
commit da293a1
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Showing 3 changed files with 13 additions and 4 deletions.
diff --git a/jim.c b/jim.c
@@ -2590,7 +2590,7 @@ int Jim_StringCompareObj(Jim_Interp *interp, Jim_Obj *firstObjPtr, Jim_Obj *seco
  * is out of range. */
 static int JimRelToAbsIndex(int len, int idx)
 {
-    if (idx < 0)
+    if (idx < 0 && idx > -INT_MAX)
         return len + idx;
     return idx;
 }
@@ -13979,9 +13979,7 @@ static int Jim_StringCoreCommand(Jim_Interp *interp, int argc, Jim_Obj *const *a
                 }
                 str = Jim_String(argv[2]);
                 len = Jim_Utf8Length(interp, argv[2]);
-                if (idx != INT_MIN && idx != INT_MAX) {
-                    idx = JimRelToAbsIndex(len, idx);
-                }
+                idx = JimRelToAbsIndex(len, idx);
                 if (idx < 0 || idx >= len || str == NULL) {
                     Jim_SetResultString(interp, "", 0);
                 }
@@ -14015,6 +14013,9 @@ static int Jim_StringCoreCommand(Jim_Interp *interp, int argc, Jim_Obj *const *a
                         return JIM_ERR;
                     }
                     idx = JimRelToAbsIndex(l2, idx);
+                    if (idx < 0) {
+                        idx = 0;
+                    }
                 }
                 else if (option == OPT_LAST) {
                     idx = l2;

diff --git a/regtest.tcl b/regtest.tcl
@@ -355,6 +355,11 @@ puts "TEST 51 PASSED"
 catch {lsearch -all -command abc def}
 puts "TEST 52 PASSED"
 
+# REGTEST 53
+# string last with invalid index
+catch {string last foo bar -1}
+puts "TEST 53 PASSED"
+
 
 # TAKE THE FOLLOWING puts AS LAST LINE
 

diff --git a/tests/string.test b/tests/string.test
@@ -449,6 +449,9 @@ test string-7.5 {string last} {
 test string-7.6 {string last} {
     string las x xxxx123xx345x678
 } 12
+test string-7.7 {string last, bad index} {
+    string last ba badbad -1
+} -1
 test string-7.13 {string last, start index} {
     ## Constrain to last 'a' should work
     string last ba badbad end-1