Fix #14575 FN constVariablePointer with std::wstring (#8301)

Author: chrchr-github

cfg/std.cfg

@@ -7130,13 +7130,30 @@ The obsolete function 'gets' is called. With 'gets' you'll get a buffer overrun
     <returnValue type="const char *"/>
     <noreturn>false</noreturn>
   </function>
+  <!-- const wchar_t* c_str() const; // until C++11 -->
+  <!-- const wchar_t* c_str() const noexcept; // since C++11 -->
+  <!-- const wchar_t* data() const; // until C++11 -->
+  <!-- const wchar_t* data() const noexcept; // since C++11 -->
+  <function name="std::wstring::c_str,std::wstring::data">
+    <use-retval/>
+    <const/>
+    <returnValue type="const wchar_t *"/>
+    <noreturn>false</noreturn>
+  </function>
   <!-- char& front(); -->
   <!-- const char& front() const; -->
   <function name="std::string::front">
     <use-retval/>
     <returnValue type="char &amp;"/>
     <noreturn>false</noreturn>
   </function>
+  <!-- wchar_t& front(); -->
+  <!-- const wchar_t& front() const; -->
+  <function name="std::wstring::front">
+    <use-retval/>
+    <returnValue type="wchar_t &amp;"/>
+    <noreturn>false</noreturn>
+  </function>
   <!-- size_t find (const string& str, size_t pos = 0) const; -->
   <!-- size_t find (const char* s, size_t pos, size_t n) const; -->
   <!-- size_t find (char c, size_t pos = 0) const;-->

test/cfg/std.cpp

@@ -5166,6 +5166,20 @@ void constVariablePointer_push_back(std::vector<T*>& d, const std::vector<T*>& s
     }
 }
 
+struct S_constVariablePointer_wstring { // #14575
+    std::wstring m;
+    const std::wstring& get() const { return m; }
+};
+
+S_constVariablePointer_wstring* g_constVariablePointer_wstring();
+
+void h_constVariablePointer_wstring(const wchar_t*);
+
+void f_constVariablePointer_wstring() {
+    S_constVariablePointer_wstring* s = g_constVariablePointer_wstring(); // cppcheck-suppress constVariablePointer
+    h_constVariablePointer_wstring(s->get().c_str());
+}
+
 std::streampos constParameterPointer_istream_tellg(std::istream* p) { // #13801
     return p->tellg();
 }
@@ -5318,4 +5332,4 @@ int containerOutOfBounds_std_initializer_list() { // #14340
     // cppcheck-suppress derefInvalidIterator
     int i = *x.end();
     return i + containerOutOfBounds_std_initializer_list_access(x);
-}
+}