C++: HashCons for throw

Author: Robert Marsh

cpp/ql/src/semmle/code/cpp/valuenumbering/HashCons.qll

@@ -119,6 +119,10 @@ private cached newtype HCBase =
   or
   HC_DeleteArrayExpr(HashCons child) {mk_DeleteArrayExpr(child, _)}
   or
+  HC_ThrowExpr(HashCons child) {mk_ThrowExpr(child, _)}
+  or
+  HC_ReThrowExpr()
+  or
   // Any expression that is not handled by the cases above is
   // given a unique number based on the expression itself.
   HC_Unanalyzable(Expr e) { not analyzableExpr(e,_) }
@@ -228,6 +232,8 @@ class HashCons extends HCBase {
     if this instanceof HC_ClassAggregateLiteral then result = "ClassAggreagateLiteral" else
     if this instanceof HC_DeleteExpr then result = "DeleteExpr" else
     if this instanceof HC_DeleteArrayExpr then result = "DeleteArrayExpr" else
+    if this instanceof HC_ThrowExpr then result = "ThrowExpr" else
+    if this instanceof HC_ReThrowExpr then result = "ReThrowExpr" else
     result = "error"
   }
 
@@ -828,6 +834,23 @@ private predicate mk_ArrayAggregateLiteral(Type t, HC_Array hca, ArrayAggregateL
   )
 }
 
+private predicate analyzableThrowExpr(ThrowExpr te) {
+  strictcount(te.getExpr().getFullyConverted()) = 1
+}
+
+private predicate mk_ThrowExpr(HashCons hc, ThrowExpr te) {
+  analyzableThrowExpr(te) and
+  hc.getAnExpr() = te.getExpr().getFullyConverted()
+}
+
+private predicate analyzableReThrowExpr(ReThrowExpr rte) {
+  any()
+}
+
+private predicate mk_ReThrowExpr(ReThrowExpr te) {
+  any()
+}
+
 /** Gets the hash-cons of expression `e`. */
 cached HashCons hashCons(Expr e) {
   exists (int val, Type t
@@ -946,6 +969,16 @@ cached HashCons hashCons(Expr e) {
     result = HC_DeleteArrayExpr(child)
   )
   or
+  exists(HashCons child
+  | mk_ThrowExpr(child, e) and
+    result = HC_ThrowExpr(child)
+  )
+  or
+  (
+    mk_ReThrowExpr(e) and
+    result = HC_ReThrowExpr()
+  )
+  or
   (
     mk_Nullptr(e) and
     result = HC_Nullptr()
@@ -987,5 +1020,7 @@ predicate analyzableExpr(Expr e, string kind) {
   (analyzableClassAggregateLiteral(e) and kind = "ClassAggregateLiteral") or
   (analyzableArrayAggregateLiteral(e) and kind = "ArrayAggregateLiteral") or
   (analyzableDeleteExpr(e) and kind = "DeleteExpr") or
-  (analyzableDeleteArrayExpr(e) and kind = "DeleteArrayExpr")
+  (analyzableDeleteArrayExpr(e) and kind = "DeleteArrayExpr") or
+  (analyzableThrowExpr(e) and kind = "ThrowExpr") or
+  (analyzableReThrowExpr(e) and kind = "ReThrowExpr")
 }

cpp/ql/test/library-tests/valuenumbering/HashCons/HashCons.expected

@@ -38,9 +38,9 @@
 | test.cpp:92:11:92:11 | x | 92:c11-c11 93:c10-c10 |
 | test.cpp:97:3:97:3 | x | 97:c3-c3 98:c3-c3 |
 | test.cpp:97:3:97:5 | ... ++ | 97:c3-c5 98:c3-c5 |
-| test.cpp:103:10:103:11 | 1 | 103:c10-c11 104:c7-c7 107:c7-c7 108:c7-c7 10:c16-c16 179:c21-c21 247:c11-c11 248:c11-c11 271:c28-c28 272:c28-c28 274:c19-c19 274:c22-c22 288:c5-c5 292:c5-c5 297:c5-c5 |
+| test.cpp:103:10:103:11 | 1 | 103:c10-c11 104:c7-c7 107:c7-c7 108:c7-c7 10:c16-c16 179:c21-c21 247:c11-c11 248:c11-c11 271:c28-c28 272:c28-c28 274:c19-c19 274:c22-c22 288:c5-c5 292:c5-c5 297:c5-c5 302:c9-c9 303:c9-c9 |
 | test.cpp:104:3:104:3 | x | 104:c3-c3 105:c3-c3 106:c3-c3 107:c3-c3 108:c3-c3 |
-| test.cpp:105:7:105:7 | 2 | 105:c7-c7 106:c7-c7 107:c11-c11 108:c11-c11 21:c16-c16 249:c11-c11 271:c24-c24 271:c31-c31 272:c24-c24 272:c31-c31 273:c24-c24 274:c15-c15 275:c15-c15 275:c19-c19 275:c22-c22 277:c15-c15 278:c15-c15 289:c5-c5 293:c5-c5 296:c5-c5 |
+| test.cpp:105:7:105:7 | 2 | 105:c7-c7 106:c7-c7 107:c11-c11 108:c11-c11 21:c16-c16 249:c11-c11 271:c24-c24 271:c31-c31 272:c24-c24 272:c31-c31 273:c24-c24 274:c15-c15 275:c15-c15 275:c19-c19 275:c22-c22 277:c15-c15 278:c15-c15 289:c5-c5 293:c5-c5 296:c5-c5 304:c9-c9 305:c9-c9 |
 | test.cpp:107:7:107:11 | ... + ... | 107:c7-c11 108:c7-c11 |
 | test.cpp:110:15:110:17 | 1 | 110:c15-c17 111:c9-c11 |
 | test.cpp:110:15:110:17 | (char *)... | 110:c15-c17 111:c9-c11 |
@@ -104,3 +104,6 @@
 | test.cpp:277:3:277:19 | new[] | 277:c3-c19 278:c3-c19 |
 | test.cpp:277:3:277:19 | {...} | 277:c3-c19 278:c3-c19 |
 | test.cpp:287:15:290:3 | {...} | 287:c15-c3 291:c15-c3 |
+| test.cpp:302:3:302:9 | throw ... | 302:c3-c9 303:c3-c9 |
+| test.cpp:304:3:304:9 | throw ... | 304:c3-c9 305:c3-c9 |
+| test.cpp:306:3:306:7 | re-throw exception  | 306:c3-c7 307:c3-c7 |

cpp/ql/test/library-tests/valuenumbering/HashCons/test.cpp

@@ -297,3 +297,12 @@ void test17() {
     1
   };
 }
+
+void test18() {
+  throw 1;
+  throw 1;
+  throw 2;
+  throw 2;
+  throw;
+  throw;
+}