Fix #12134 false negative: passedByValue (#5607)

Author: chrchr-github

cfg/std.cfg

@@ -6977,6 +6977,7 @@ The obsolete function 'gets' is called. With 'gets' you'll get a buffer overrun
   </function>
   <function name="std::string::substr">
     <use-retval/>
+    <const/>
     <returnValue type="std::string"/>
     <noreturn>false</noreturn>
     <arg nr="1" default="0" direction="in">
@@ -6990,6 +6991,7 @@ The obsolete function 'gets' is called. With 'gets' you'll get a buffer overrun
   </function>
   <function name="std::wstring::substr">
     <use-retval/>
+    <const/>
     <returnValue type="std::wstring"/>
     <noreturn>false</noreturn>
     <arg nr="1" default="0" direction="in">
@@ -7003,6 +7005,7 @@ The obsolete function 'gets' is called. With 'gets' you'll get a buffer overrun
   </function>
   <function name="std::basic_string::substr">
     <use-retval/>
+    <const/>
     <returnValue type="std::basic_string"/>
     <noreturn>false</noreturn>
     <arg nr="1" default="0" direction="in">

lib/checkother.cpp

@@ -3596,7 +3596,7 @@ void CheckOther::checkShadowVariables()
     }
 }
 
-void CheckOther::shadowError(const Token *var, const Token *shadowed, std::string type)
+void CheckOther::shadowError(const Token *var, const Token *shadowed, const std::string& type)
 {
     ErrorPath errorPath;
     errorPath.emplace_back(shadowed, "Shadowed declaration");

lib/checkother.h

@@ -284,7 +284,7 @@ class CPPCHECKLIB CheckOther : public Check {
     void accessMovedError(const Token *tok, const std::string &varname, const ValueFlow::Value *value, bool inconclusive);
     void funcArgNamesDifferent(const std::string & functionName, nonneg int index, const Token* declaration, const Token* definition);
     void funcArgOrderDifferent(const std::string & functionName, const Token * declaration, const Token * definition, const std::vector<const Token*> & declarations, const std::vector<const Token*> & definitions);
-    void shadowError(const Token *var, const Token *shadowed, std::string type);
+    void shadowError(const Token *var, const Token *shadowed, const std::string& type);
     void knownArgumentError(const Token *tok, const Token *ftok, const ValueFlow::Value *value, const std::string &varexpr, bool isVariableExpressionHidden);
     void knownPointerToBoolError(const Token* tok, const ValueFlow::Value* value);
     void comparePointersError(const Token *tok, const ValueFlow::Value *v1, const ValueFlow::Value *v2);

test/cfg/std.cpp

@@ -4638,6 +4638,13 @@ void string_view_unused(std::string_view v)
     v.substr(1, 3);
 }
 
+// cppcheck-suppress passedByValue
+void string_substr(std::string s)
+{
+    // cppcheck-suppress ignoredReturnValue
+    s.substr(1, 3);
+}
+
 void stdspan()
 {
 #ifndef __cpp_lib_span