Remove inline suppression and fix false positive.

lib/astutils.cpp

@@ -1404,6 +1404,22 @@ bool FwdAnalysis::possiblyAliased(const Token *expr, const Token *startToken) co
         if (tok->str() == "{" && tok->scope()->type == Scope::eFunction)
             break;
 
+        if (Token::Match(tok, "%name% (") && !Token::Match(tok, "if|while|for")) {
+            // Is argument passed by reference?
+            const std::vector<const Token*> args = getArguments(tok);
+            for (unsigned int argnr = 0; argnr < args.size(); ++argnr) {
+                if (!Token::Match(args[argnr], "%name%|.|::"))
+                    continue;
+                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;
+                }
+            }
+            continue;
+        }
+
         const Token *addrOf = nullptr;
         if (Token::Match(tok, "& %name% ="))
             addrOf = tok->tokAt(2)->astOperand2();

lib/preprocessor.cpp

@@ -822,7 +822,6 @@ void Preprocessor::getErrorMessages(ErrorLogger *errorLogger, const Settings *se
 {
     Settings settings2(*settings);
     Preprocessor preprocessor(settings2, errorLogger);
-    // cppcheck-suppress unreadVariable // FP
     settings2.checkConfiguration = true;
     preprocessor.missingInclude(emptyString, 1, emptyString, UserHeader);
     preprocessor.missingInclude(emptyString, 1, emptyString, SystemHeader);

test/testunusedvar.cpp

@@ -2161,14 +2161,25 @@ private:
                               "}\n");
         ASSERT_EQUALS("[test.cpp:3]: (style) Variable 'x' is assigned a value that is never used.\n", errout.str());
 
-        functionVariableUsage("void fun() {\n"
+        functionVariableUsage("void dostuff(int x);\n"
+                              "void fun() {\n"
                               "  int x = 1;\n"
                               "  while (c) {\n"
                               "    dostuff(x);\n"
                               "    if (y) { x=10; break; }\n"
                               "  }\n"
                               "}\n");
-        ASSERT_EQUALS("[test.cpp:5]: (style) Variable 'x' is assigned a value that is never used.\n", errout.str());
+        ASSERT_EQUALS("[test.cpp:6]: (style) Variable 'x' is assigned a value that is never used.\n", errout.str());
+
+        functionVariableUsage("void dostuff(int &x);\n"
+                              "void fun() {\n"
+                              "  int x = 1;\n"
+                              "  while (c) {\n"
+                              "    dostuff(x);\n"
+                              "    if (y) { x=10; break; }\n"
+                              "  }\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
 
         functionVariableUsage("void fun() {\n"
                               "  int x = 0;\n"
@@ -3170,11 +3181,25 @@ private:
     }
 
     void localvaralias14() { // #5619
+        functionVariableUsage("char * dostuff(char *p);\n"
+                              "void f() {\n"
+                              "    char a[4], *p=a;\n"
+                              "    p = dostuff(p);\n"
+                              "}");
+        ASSERT_EQUALS("[test.cpp:4]: (style) Variable 'p' is assigned a value that is never used.\n", errout.str());
+
+        functionVariableUsage("char * dostuff(char *&p);\n"
+                              "void f() {\n"
+                              "    char a[4], *p=a;\n"
+                              "    p = dostuff(p);\n"
+                              "}");
+        ASSERT_EQUALS("", errout.str()); // TODO: we can warn in this special case; variable is local and there are no function calls after the assignment
+
         functionVariableUsage("void f() {\n"
                               "    char a[4], *p=a;\n"
                               "    p = dostuff(p);\n"
                               "}");
-        ASSERT_EQUALS("[test.cpp:3]: (style) Variable 'p' is assigned a value that is never used.\n", errout.str());
+        ASSERT_EQUALS("", errout.str()); // TODO: we can warn in this special case; variable is local and there are no function calls after the assignment
     }
 
     void localvaralias15() { // #6315