ValueFlow: skip values that cause false assertion condition

Author: danmar

lib/valueflow.cpp

@@ -1463,6 +1463,19 @@ static bool valueFlowForward(Token * const               startToken,
             }
         }
 
+        else if (Token::Match(tok2, "assert|ASSERT (") && Token::simpleMatch(tok2->linkAt(1), ") ;")) {
+            const Token * const arg = tok2->next()->astOperand2();
+            if (arg != nullptr && arg->str() != ",") {
+                // Should scope be skipped because variable value is checked?
+                for (std::list<ValueFlow::Value>::const_iterator it = values.begin(); it != values.end();) {
+                    if (conditionIsFalse(arg, getProgramMemory(tok2, varid, *it)))
+                        values.erase(it++);
+                    else
+                        ++it;
+                }
+            }
+        }
+
         else if (tok2->str() == "}" && indentlevel == varusagelevel) {
             ++number_of_if;
 

test/testvalueflow.cpp

@@ -1796,6 +1796,20 @@ class TestValueFlow : public TestFixture {
                "}";
         ASSERT_EQUALS(false, testValueOfX(code, 6U, 5));
 
+        // assert after for loop..
+        code = "static void f() {\n"
+               "  int x;\n"
+               "  int ctls[10];\n"
+               "  for (x = 0; x <= 10; x++) {\n"
+               "    if (cond)\n"
+               "      break;\n"
+               "  }\n"
+               "  assert(x <= 10);\n"
+               "  ctls[x] = 123;\n" // <- x can't be 11
+               "}\n";
+        ASSERT_EQUALS(false, testValueOfX(code, 9U, 11));
+
+
         // hang
         code = "void f() {\n"
                "  for(int i = 0; i < 20; i++)\n"