Avoid generating string representation when comparing the empty string.

1 files changed, 51 insertions, 5 deletions

diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index af44323..728a847 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -5440,22 +5440,58 @@ TEBCresume(
 		}
 	    } else {
 		/*
-		 * strcmp can't do a simple memcmp in order to handle the
-		 * special Tcl \xC0\x80 null encoding for utf-8.
+		 * In order to handle the special Tcl \xC0\x80 null encoding
+		 * for utf-8, strcmp can't do a simple memcmp.
 		 */
 
-		s1 = TclGetStringFromObj(valuePtr, &s1len);
-		s2 = TclGetStringFromObj(value2Ptr, &s2len);
+		{
+		    int empty;
+		    if ((empty = TclCheckEmptyString(valuePtr)) > 0) {
+			switch (TclCheckEmptyString(value2Ptr)) {
+			    case -1:
+				s1 = "";
+				s1len = 0;
+				s2 = TclGetStringFromObj(value2Ptr, &s2len);
+				break;
+			    case 0:
+				match = -1;
+				goto matchdone;
+			    case 1:
+				match = 0;
+				goto matchdone;
+			}
+		    } else if (TclCheckEmptyString(value2Ptr) > 0) {
+			switch (empty) {
+			    case -1:
+				s2 = "";
+				s2len = 0;
+				s1 = TclGetStringFromObj(valuePtr, &s1len);
+				break;
+			    case 0:
+				match = 1;
+				goto matchdone;
+			    case 1:
+				match = 0;
+				goto matchdone;
+			}
+		    } else {
+			s1 = TclGetStringFromObj(valuePtr, &s1len);
+			s2 = TclGetStringFromObj(value2Ptr, &s2len);
+		    }
+		}
+
+
 		if (checkEq) {
 		    memCmpFn = memcmp;
 		} else {
 		    memCmpFn = (memCmpFn_t) TclpUtfNcmp2;
 		}
+
 	    }
 
 	    if (checkEq && (s1len != s2len)) {
 		match = 1;
-	    } else {
+	    }  else {
 		/*
 		 * The comparison function should compare up to the minimum
 		 * byte length only.
@@ -5468,6 +5504,8 @@ TEBCresume(
 	    }
 	}
 
+	matchdone:
+
 	/*
 	 * Make sure only -1,0,1 is returned
 	 * TODO: consider peephole opt.
@@ -6142,6 +6180,14 @@ TEBCresume(
 	value2Ptr = OBJ_AT_TOS;
 	valuePtr = OBJ_UNDER_TOS;
 
+	/*
+	    Try to determine, without triggering generation of a string
+	    representation, whether one value is not a number.
+	*/
+	if (TclCheckEmptyString(valuePtr) > 0 || TclCheckEmptyString(value2Ptr) > 0) {
+	    goto stringCompare;
+	}
+
 	if (GetNumberFromObj(NULL, valuePtr, &ptr1, &type1) != TCL_OK
 		|| GetNumberFromObj(NULL, value2Ptr, &ptr2, &type2) != TCL_OK) {
 	    /*