Fix #14717 (FP: same exprId for different expressions leads to wrong redundantAssignment)

Author: danmar

lib/symboldatabase.cpp

@@ -1643,10 +1643,30 @@ namespace {
                 continue;
             }
 
+            const auto getExprIdForOperand = [](const Token* tok) -> int {
+                if (!tok)
+                    return 0;
+
+                int otherExprId = 0;
+
+                // Look through all referenced tokens.
+                // If two exprIds are found and one matches tok->exprId(), return the other.
+                // Otherwise, default to returning tok->exprId().
+                for (const auto& ref: followAllReferences(tok)) {
+                    const int refExprId = ref.token->exprId();
+                    if (refExprId != 0 && refExprId != tok->exprId()) {
+                        if (otherExprId != 0 && otherExprId != refExprId)
+                            return tok->exprId();
+                        otherExprId = refExprId;
+                    }
+                }
+                return otherExprId != 0 ? otherExprId : tok->exprId();
+            };
+
             ExprIdKey key;
             key.parentOp = tok->astParent()->str();
-            key.operand1 = op1 ? op1->exprId() : 0;
-            key.operand2 = op2 ? op2->exprId() : 0;
+            key.operand1 = getExprIdForOperand(op1);
+            key.operand2 = getExprIdForOperand(op2);
 
             if (tok->astParent()->isCast() && tok->astParent()->str() == "(") {
                 const Token* typeStartToken;
@@ -1665,19 +1685,6 @@ namespace {
                 key.parentOp += type;
             }
 
-            for (const auto& ref: followAllReferences(op1)) {
-                if (ref.token->exprId() != 0) { // cppcheck-suppress useStlAlgorithm
-                    key.operand1 = ref.token->exprId();
-                    break;
-                }
-            }
-            for (const auto& ref: followAllReferences(op2)) {
-                if (ref.token->exprId() != 0) { // cppcheck-suppress useStlAlgorithm
-                    key.operand2 = ref.token->exprId();
-                    break;
-                }
-            }
-
             if (key.operand1 > key.operand2 && key.operand2 &&
                 Token::Match(tok->astParent(), "%or%|%oror%|+|*|&|&&|^|==|!=")) {
                 // In C++ the order of operands of + might matter

test/testvarid.cpp

@@ -262,6 +262,7 @@ class TestVarID : public TestFixture {
         TEST_CASE(exprid12);
         TEST_CASE(exprid13);
         TEST_CASE(exprid14);
+        TEST_CASE(exprid15);
 
         TEST_CASE(structuredBindings);
     }
@@ -4518,6 +4519,24 @@ class TestVarID : public TestFixture {
         ASSERT_EQUALS(exp, tokenize(code, s)); // don't crash
     }
 
+    void exprid15()
+    {
+        // #14717
+        const char code[] = "#define MAX(a, b) (((a) > (b)) ? (a) : (b))\n"
+                            "\n"
+                            "void f(char *d) {\n"
+                            "    const char *p = &d[0];\n"
+                            "    int a = 1 / MAX(1, p[0]);\n"
+                            "    a = 1 / MAX(1, p[1]);\n"
+                            "}\n";
+        const char exp[] = "3: void f ( char * d ) {\n"
+                           "4: const char * p@2 ; p@2 =@UNIQUE &@UNIQUE d@1 [@UNIQUE 0 ] ;\n"
+                           "5: int a@3 ; a@3 =@UNIQUE 1 /@UNIQUE $( $( 1 $>@UNIQUE $( p@2 [@9 0 ] $) $) $?@UNIQUE $( 1 $) $:@UNIQUE $( p@2 [@9 0 ] $) $) ;\n"
+                           "6: a@3 =@UNIQUE 1 /@UNIQUE $( $( 1 $>@UNIQUE $( p@2 [@15 1 ] $) $) $?@UNIQUE $( 1 $) $:@UNIQUE $( p@2 [@15 1 ] $) $) ;\n"
+                           "7: }\n";
+        ASSERT_EQUALS(exp, tokenizeExpr(code));
+    }
+
     void structuredBindings() {
         const char code[] = "int foo() { auto [x,y] = xy(); return x+y; }";
         ASSERT_EQUALS("1: int foo ( ) { auto [ x@1 , y@2 ] = xy ( ) ; return x@1 + y@2 ; }\n",