Fix string iteration logic in wxFTP::Pwd()

wxString iterators can't be dereferenced once they reach the end of the
string, so compare them with end rather than checking if the value they point
to is non-NUL.

This makes wxFTP::Pwd() actually work, which was apparently broken since quite
some time (perhaps ever since c9f7896861 9+
years ago).

See #17679.

(cherry picked from commit d0c57dbef0)

docs/changes.txt

@@ -587,6 +587,7 @@ All:
 
 - Fix wxFileName::MakeRelativeTo() for directory relatively to itself.
 - Fix wxLocale::IsOk() return true even if setting the locale failed.
+- Fix wxFTP::Pwd() to actually work.
 - Null-terminate wxApp::argv for compatibility with the real argv.
 
 Unix:

src/common/ftp.cpp

@@ -459,20 +459,21 @@ wxString wxFTP::Pwd()
     {
         // the result is at least that long if CheckCommand() succeeded
         wxString::const_iterator p = m_lastResult.begin() + LEN_CODE + 1;
-        if ( *p != wxT('"') )
+        const wxString::const_iterator end = m_lastResult.end();
+        if ( p == end || *p != wxT('"') )
         {
             wxLogDebug(wxT("Missing starting quote in reply for PWD: %s"),
-                       wxString(p, m_lastResult.end()));
+                       wxString(p, end));
         }
         else
         {
-            for ( ++p; (bool)*p; ++p ) // FIXME-DMARS
+            for ( ++p; p != end; ++p )
             {
                 if ( *p == wxT('"') )
                 {
                     // check if the quote is doubled
                     ++p;
-                    if ( !*p || *p != wxT('"') )
+                    if ( p == end || *p != wxT('"') )
                     {
                         // no, this is the end
                         break;
@@ -484,7 +485,7 @@ wxString wxFTP::Pwd()
                 path += *p;
             }
 
-            if ( !*p )
+            if ( p != end )
             {
                 wxLogDebug(wxT("Missing ending quote in reply for PWD: %s"),
                            m_lastResult.c_str() + LEN_CODE + 1);

tests/uris/ftp.cpp

@@ -57,6 +57,7 @@ private:
         CPPUNIT_TEST( List );
         CPPUNIT_TEST( Download );
         CPPUNIT_TEST( FileSize );
+        CPPUNIT_TEST( Pwd );
         CPPUNIT_TEST( Misc );
 #ifndef FTP_ANONYMOUS
         CPPUNIT_TEST( Upload );
@@ -66,6 +67,7 @@ private:
     void List();
     void Download();
     void FileSize();
+    void Pwd();
     void Misc();
     void Upload();
 
@@ -148,9 +150,16 @@ void FTPTestCase::FileSize()
     CPPUNIT_ASSERT( size != -1 );
 }
 
+void FTPTestCase::Pwd()
+{
+    CPPUNIT_ASSERT_EQUAL( "/", m_ftp->Pwd() );
+
+    CPPUNIT_ASSERT( m_ftp->ChDir(directory) );
+    CPPUNIT_ASSERT_EQUAL( directory, m_ftp->Pwd() );
+}
+
 void FTPTestCase::Misc()
 {
-
     CPPUNIT_ASSERT( m_ftp->SendCommand(wxT("STAT")) == '2' );
     CPPUNIT_ASSERT( m_ftp->SendCommand(wxT("HELP SITE")) == '2' );
 }