Partial fix for #9407 FN redundant assignment/unreadVariable (danmar#3651)

chrchr-github · web-flow · commit 0a99e3b6fc94 · 2022-02-12T15:32:08.000+01:00
diff --git a/lib/astutils.cpp b/lib/astutils.cpp
@@ -3339,8 +3339,11 @@ bool FwdAnalysis::possiblyAliased(const Token *expr, const Token *startToken) co
                 if (tok->function() && tok->function()->getArgumentVar(argnr) && !tok->function()->getArgumentVar(argnr)->isReference() && !tok->function()->isConst())
                     continue;
                 for (const Token *subexpr = expr; subexpr; subexpr = subexpr->astOperand1()) {
-                    if (isSameExpression(mCpp, macro, subexpr, args[argnr], mLibrary, pure, followVar))
-                        return true;
+                    if (isSameExpression(mCpp, macro, subexpr, args[argnr], mLibrary, pure, followVar)) {
+                        const Scope* scope = expr->scope(); // if there is no other variable, assume no aliasing
+                        if (scope->varlist.size() > 1)
+                            return true;
+                    }
                 }
             }
             continue;
diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
@@ -126,6 +126,7 @@ class TestUnusedVar : public TestFixture {
         TEST_CASE(localvar58); // #9901 - increment false positive
         TEST_CASE(localvar59); // #9737
         TEST_CASE(localvar60);
+        TEST_CASE(localvar61); // #9407
         TEST_CASE(localvarloops); // loops
         TEST_CASE(localvaralias1);
         TEST_CASE(localvaralias2); // ticket #1637
@@ -3292,6 +3293,16 @@ class TestUnusedVar : public TestFixture {
         ASSERT_EQUALS("", errout.str());
     }
 
+    void localvar61() { // #9407
+        functionVariableUsage("void g(int& i);\n"
+                              "void f() {\n"
+                              "    int var = 0;\n"
+                              "    g(var);\n"
+                              "    var = 2;\n"
+                              "}\n");
+        ASSERT_EQUALS("[test.cpp:5]: (style) Variable 'var' is assigned a value that is never used.\n", errout.str());
+    }
+
     void localvarloops() {
         // loops
         functionVariableUsage("void fun(int c) {\n"
@@ -3318,7 +3329,7 @@ class TestUnusedVar : public TestFixture {
                               "    if (y) { x=10; break; }\n"
                               "  }\n"
                               "}");
-        ASSERT_EQUALS("", errout.str()); // TODO : in this special case we can ignore that x is aliased. x is local and there are no function calls after the assignment
+        ASSERT_EQUALS("[test.cpp:6]: (style) Variable 'x' is assigned a value that is never used.\n", errout.str());
 
         functionVariableUsage("void fun() {\n"
                               "  int x = 0;\n"

Original file line number	Diff line number	Diff line change
`@@ -3339,8 +3339,11 @@ bool FwdAnalysis::possiblyAliased(const Token expr, const Token startToken) co`
`3339`	`3339`	`if (tok->function() && tok->function()->getArgumentVar(argnr) && !tok->function()->getArgumentVar(argnr)->isReference() && !tok->function()->isConst())`
`3340`	`3340`	`continue;`
`3341`	`3341`	`for (const Token *subexpr = expr; subexpr; subexpr = subexpr->astOperand1()) {`
`3342`		`- if (isSameExpression(mCpp, macro, subexpr, args[argnr], mLibrary, pure, followVar))`
`3343`		`- return true;`
	`3342`	`+ if (isSameExpression(mCpp, macro, subexpr, args[argnr], mLibrary, pure, followVar)) {`
	`3343`	`+ const Scope* scope = expr->scope(); // if there is no other variable, assume no aliasing`
	`3344`	`+ if (scope->varlist.size() > 1)`
	`3345`	`+ return true;`
	`3346`	`+ }`
`3344`	`3347`	`}`
`3345`	`3348`	`}`
`3346`	`3349`	`continue;`