Fix #13327 FN mismatchingContainers for struct member and c_str() (danmar#7024)

Co-authored-by: Paul Fultz II <[email protected]>

Author: chrchr-github

lib/checkstl.cpp

@@ -725,14 +725,36 @@ static bool isSameIteratorContainerExpression(const Token* tok1,
     return false;
 }
 
+// First it groups the lifetimes together using std::partition with the lifetimes that refer to the same token or token of a subexpression.
+// Then it finds the lifetime in that group that refers to the "highest" parent using std::min_element and adds that to the vector.
+static std::vector<ValueFlow::Value> pruneLifetimes(std::vector<ValueFlow::Value> lifetimes)
+{
+    std::vector<ValueFlow::Value> result;
+    auto start = lifetimes.begin();
+    while (start != lifetimes.end())
+    {
+        const Token* tok1 = start->tokvalue;
+        auto it = std::partition(start, lifetimes.end(), [&](const ValueFlow::Value& v) {
+            const Token* tok2 = v.tokvalue;
+            return astHasToken(tok1, tok2) || astHasToken(tok2, tok1);
+        });
+        auto root = std::min_element(start, it, [](const ValueFlow::Value& x, const ValueFlow::Value& y) {
+            return x.tokvalue != y.tokvalue && astHasToken(x.tokvalue, y.tokvalue);
+        });
+        result.push_back(*root);
+        start = it;
+    }
+    return result;
+}
+
 static ValueFlow::Value getLifetimeIteratorValue(const Token* tok, MathLib::bigint path = 0)
 {
     auto findIterVal = [](const std::vector<ValueFlow::Value>& values, const std::vector<ValueFlow::Value>::const_iterator beg) {
         return std::find_if(beg, values.cend(), [](const ValueFlow::Value& v) {
             return v.lifetimeKind == ValueFlow::Value::LifetimeKind::Iterator;
         });
     };
-    std::vector<ValueFlow::Value> values = ValueFlow::getLifetimeObjValues(tok, false, path);
+    std::vector<ValueFlow::Value> values = pruneLifetimes(ValueFlow::getLifetimeObjValues(tok, false, path));
     auto it = findIterVal(values, values.begin());
     if (it != values.end()) {
         auto it2 = findIterVal(values, it + 1);

test/teststl.cpp

@@ -70,6 +70,7 @@ class TestStl : public TestFixture {
         TEST_CASE(iterator28); // #10450
         TEST_CASE(iterator29);
         TEST_CASE(iterator30);
+        TEST_CASE(iterator31);
         TEST_CASE(iteratorExpression);
         TEST_CASE(iteratorSameExpression);
         TEST_CASE(mismatchingContainerIterator);
@@ -1900,6 +1901,27 @@ class TestStl : public TestFixture {
         ASSERT_EQUALS("", errout_str());
     }
 
+    void iterator31()
+    {
+        check("struct S {\n" // #13327
+              "    std::string a;\n"
+              "};\n"
+              "struct T {\n"
+              "    S s;\n"
+              "};\n"
+              "bool f(const S& s) {\n"
+              "    std::string b;\n"
+              "    return s.a.c_str() == b.c_str();\n"
+              "}\n"
+              "bool g(const T& t) {\n"
+              "    std::string b;\n"
+              "    return t.s.a.c_str() == b.c_str();\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:9]: (error) Iterators of different containers 's.a' and 'b' are used together.\n"
+                      "[test.cpp:13]: (error) Iterators of different containers 't.s.a' and 'b' are used together.\n",
+                      errout_str());
+    }
+
     void iteratorExpression() {
         check("std::vector<int>& f();\n"
               "std::vector<int>& g();\n"