Fix #14709 FP memleak using IS_NULL() macro (#8522)

Author: chrchr-github

lib/astutils.cpp

@@ -400,6 +400,8 @@ const Token * astIsVariableComparison(const Token *tok, const std::string &comp,
     }
     while (ret && ret->str() == ".")
         ret = ret->astOperand2();
+    while (ret && ret->isCast())
+        ret = ret->astOperand2() ? ret->astOperand2() : ret->astOperand1();
     if (ret && ret->str() == "=" && ret->astOperand1() && ret->astOperand1()->varId())
         ret = ret->astOperand1();
     else if (ret && ret->varId() == 0U)

test/testleakautovar.cpp

@@ -154,6 +154,7 @@ class TestLeakAutoVar : public TestFixture {
         TEST_CASE(ifelse27);
         TEST_CASE(ifelse28); // #11038
         TEST_CASE(ifelse29);
+        TEST_CASE(ifelse30);
 
         // switch
         TEST_CASE(switch1);
@@ -2390,6 +2391,22 @@ class TestLeakAutoVar : public TestFixture {
         ASSERT_EQUALS("", errout_str()); // don't crash
     }
 
+    void ifelse30() {
+        check("void f(void** pp) {\n" // #14709
+              "    void* p = malloc(8);\n"
+              "    if ((void*)p == 0)\n"
+              "        return;\n"
+              "    *pp = p;\n"
+              "}\n"
+              "void g(void** pp) {\n"
+              "    void* p = malloc(8);\n"
+              "    if (static_cast<void*>(p) == 0)\n"
+              "        return;\n"
+              "    *pp = p;\n"
+              "}\n", dinit(CheckOptions, $.cpp = true));
+        ASSERT_EQUALS("", errout_str());
+    }
+
     void switch1() {
         check("void f() {\n"
               "    char *p = 0;\n"