Fix #12188 FN uninitvar with increment of struct member (#5665)

lib/astutils.cpp

@@ -3265,6 +3265,18 @@ static ExprUsage getFunctionUsage(const Token* tok, int indirect, const Settings
     return ExprUsage::Inconclusive;
 }
 
+bool isLeafDot(const Token* tok)
+{
+    if (!tok)
+        return false;
+    const Token * parent = tok->astParent();
+    if (!Token::simpleMatch(parent, "."))
+        return false;
+    if (parent->astOperand2() == tok && !Token::simpleMatch(parent->astParent(), "."))
+        return true;
+    return isLeafDot(parent);
+}
+
 ExprUsage getExprUsage(const Token* tok, int indirect, const Settings* settings, bool cpp)
 {
     const Token* parent = tok->astParent();
@@ -3285,6 +3297,13 @@ ExprUsage getExprUsage(const Token* tok, int indirect, const Settings* settings,
             !parent->isUnaryOp("&") &&
             !(astIsRHS(tok) && isLikelyStreamRead(cpp, parent)))
             return ExprUsage::Used;
+        if (isLeafDot(tok)) {
+            const Token* op = parent->astParent();
+            while (Token::simpleMatch(op, "."))
+                op = op->astParent();
+            if (Token::Match(op, "%assign%|++|--") && op->str() != "=")
+                return ExprUsage::Used;
+        }
         if (Token::simpleMatch(parent, "=") && astIsRHS(tok)) {
             const Token* const lhs  = parent->astOperand1();
             if (lhs && lhs->variable() && lhs->variable()->isReference() && lhs == lhs->variable()->nameToken())

lib/astutils.h

@@ -418,6 +418,8 @@ bool isCPPCast(const Token* tok);
 
 bool isConstVarExpression(const Token* tok, std::function<bool(const Token*)> skipPredicate = nullptr);
 
+bool isLeafDot(const Token* tok);
+
 enum class ExprUsage { None, NotUsed, PassedByReference, Used, Inconclusive };
 
 ExprUsage getExprUsage(const Token* tok, int indirect, const Settings* settings, bool cpp);

lib/checkuninitvar.cpp

@@ -1596,18 +1596,6 @@ void CheckUninitVar::uninitStructMemberError(const Token *tok, const std::string
                 "$symbol:" + membername + "\nUninitialized struct member: $symbol", CWE_USE_OF_UNINITIALIZED_VARIABLE, Certainty::normal);
 }
 
-static bool isLeafDot(const Token* tok)
-{
-    if (!tok)
-        return false;
-    const Token * parent = tok->astParent();
-    if (!Token::simpleMatch(parent, "."))
-        return false;
-    if (parent->astOperand2() == tok && !Token::simpleMatch(parent->astParent(), "."))
-        return true;
-    return isLeafDot(parent);
-}
-
 void CheckUninitVar::valueFlowUninit()
 {
     logChecker("CheckUninitVar::valueFlowUninit");

test/testuninitvar.cpp

@@ -7215,6 +7215,42 @@ private:
                         "  foo(&my_st);\n"
                         "}\n");
         ASSERT_EQUALS("", errout.str());
+
+        valueFlowUninit("struct S {\n" // #12188
+                        "    int i;\n"
+                        "    struct T { int j; } t;\n"
+                        "};\n"
+                        "void f() {\n"
+                        "    S s;\n"
+                        "    ++s.i;\n"
+                        "}\n"
+                        "void g() {\n"
+                        "    S s;\n"
+                        "    s.i--;\n"
+                        "}\n"
+                        "void h() {\n"
+                        "    S s;\n"
+                        "    s.i &= 3;\n"
+                        "}\n"
+                        "void k() {\n"
+                        "    S s;\n"
+                        "    if (++s.i < 3) {}\n"
+                        "}\n"
+                        "void m() {\n"
+                        "    S s;\n"
+                        "    ++s.t.j;\n"
+                        "}\n"
+                        "void n() {\n"
+                        "    S s;\n"
+                        "    if (s.t.j-- < 3) {}\n"
+                        "}\n");
+        ASSERT_EQUALS("[test.cpp:7]: (error) Uninitialized variable: s.i\n"
+                      "[test.cpp:11]: (error) Uninitialized variable: s.i\n"
+                      "[test.cpp:15]: (error) Uninitialized variable: s.i\n"
+                      "[test.cpp:19]: (error) Uninitialized variable: s.i\n"
+                      "[test.cpp:23]: (error) Uninitialized variable: s.t.j\n"
+                      "[test.cpp:27]: (error) Uninitialized variable: s.t.j\n",
+                      errout.str());
     }
 
     void uninitvar_memberfunction() {