fix #13098: False negative: memory leak not found when deallocation is conditional (regression) (danmar#6989)

Author: ludviggunne

lib/checkleakautovar.cpp

@@ -450,6 +450,16 @@ bool CheckLeakAutoVar::checkScope(const Token * const startToken,
 
         // if/else
         else if (Token::simpleMatch(tok, "if (")) {
+
+            bool skipIfBlock = false;
+            bool skipElseBlock = false;
+            const Token *condTok = tok->astSibling();
+
+            if (condTok->hasKnownIntValue()) {
+                skipIfBlock = !condTok->getKnownIntValue();
+                skipElseBlock = !skipIfBlock;
+            }
+
             // Parse function calls inside the condition
 
             const Token * closingParenthesis = tok->linkAt(1);
@@ -565,13 +575,13 @@ bool CheckLeakAutoVar::checkScope(const Token * const startToken,
                     return ChildrenToVisit::none;
                 });
 
-                if (!checkScope(closingParenthesis->next(), varInfo1, notzero, recursiveCount)) {
+                if (!skipIfBlock && !checkScope(closingParenthesis->next(), varInfo1, notzero, recursiveCount)) {
                     varInfo.clear();
                     continue;
                 }
                 closingParenthesis = closingParenthesis->linkAt(1);
                 if (Token::simpleMatch(closingParenthesis, "} else {")) {
-                    if (!checkScope(closingParenthesis->tokAt(2), varInfo2, notzero, recursiveCount)) {
+                    if (!skipElseBlock && !checkScope(closingParenthesis->tokAt(2), varInfo2, notzero, recursiveCount)) {
                         varInfo.clear();
                         return false;
                     }

test/testleakautovar.cpp

@@ -176,6 +176,7 @@ class TestLeakAutoVar : public TestFixture {
         TEST_CASE(return8);
         TEST_CASE(return9);
         TEST_CASE(return10);
+        TEST_CASE(return11); // #13098
 
         // General tests: variable type, allocation type, etc
         TEST_CASE(test1);
@@ -1686,7 +1687,7 @@ class TestLeakAutoVar : public TestFixture {
               "    free(p);\n"
               "    if (q == NULL)\n"
               "        return;\n"
-              "    free(q)\n"
+              "    free(q);\n"
               "}");
         ASSERT_EQUALS("[test.c:3] -> [test.c:8]: (error) Memory pointed to by 'p' is freed twice.\n", errout_str());
     }
@@ -2745,6 +2746,18 @@ class TestLeakAutoVar : public TestFixture {
         ASSERT_EQUALS("[test.cpp:3] -> [test.cpp:4]: (error) Returning/dereferencing 'p' after it is deallocated / released\n", errout_str());
     }
 
+    void return11() { // #13098
+        check("char malloc_memleak(void) {\n"
+              "    bool flag = false;\n"
+              "    char *ptr = malloc(10);\n"
+              "    if (flag) {\n"
+              "        free(ptr);\n"
+              "    }\n"
+              "    return 'a';\n"
+              "}\n", true);
+        ASSERT_EQUALS("[test.cpp:7]: (error) Memory leak: ptr\n", errout_str());
+    }
+
     void test1() {
         check("void f(double*&p) {\n" // 3809
               "    p = malloc(0x100);\n"