Fix #10526 FP: negativeIndex if function call is made after index check (#4052)

* Fix #10526 FP: negativeIndex if function call is made after index check

* Improve container check

* Format

Author: chrchr-github

lib/valueflow.cpp

@@ -2253,10 +2253,13 @@ struct ValueFlowAnalyzer : Analyzer {
         } else if (getSettings()->library.getFunction(tok)) {
             // Assume library function doesn't modify user-global variables
             return Action::None;
-            // Function cast does not modify global variables
+        } else if (Token::simpleMatch(tok->astParent(), ".") && astIsContainer(tok->astParent()->astOperand1())) {
+            // Assume container member function doesn't modify user-global variables
+            return Action::None;
         } else if (tok->tokType() == Token::eType && astIsPrimitive(tok->next())) {
+            // Function cast does not modify global variables
             return Action::None;
-        } else if (Token::Match(tok, "%name% (")) {
+        } else if (!tok->isKeyword() && Token::Match(tok, "%name% (")) {
             return Action::Invalid;
         }
         return Action::None;

test/testbufferoverrun.cpp

@@ -197,6 +197,7 @@ class TestBufferOverrun : public TestFixture {
         TEST_CASE(array_index_negative2);    // ticket #3063
         TEST_CASE(array_index_negative3);
         TEST_CASE(array_index_negative4);
+        TEST_CASE(array_index_negative5);    // #10526
         TEST_CASE(array_index_for_decr);
         TEST_CASE(array_index_varnames);     // FP: struct member #1576, FN: #1586
         TEST_CASE(array_index_for_continue); // for,continue
@@ -2093,6 +2094,24 @@ class TestBufferOverrun : public TestFixture {
         ASSERT_EQUALS("", errout.str());
     }
 
+    void array_index_negative5() // #10526
+    {
+        check("int i;\n"
+              "std::vector<int> v;\n"
+              "bool f() {\n"
+              "    if (i != 0) {\n"
+              "        if (v.begin() != v.end()) {\n"
+              "            if (i < 0)\n"
+              "                return false;\n"
+              "            const int a[4] = { 0, 1, 2, 3 };\n"
+              "            return a[i - 1] > 0;\n"
+              "        }\n"
+              "    }\n"
+              "    return false;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void array_index_for_decr() {
         check("void f()\n"
               "{\n"