Don't crash in wxFFile::Eof() and Error() if file is closed

Assert and return false instead, this is more developer-friendly.

Add unit tests to check that these functions really work as expected when
called on a closed file.

Closes #17828.

docs/changes.txt

@@ -84,6 +84,7 @@ All:
   wxEvtHandler and/or wxTrackable in C++11 code (Raul Tambre, mmarsan).
 - Update bundled expat to 2.2.0 (Catalin Raceanu).
 - Add wxCMD_LINE_HIDDEN wxCmdLineParser flag (Lauri Nurmi).
+- Don't crash in wxFFile::Eof() or Error() on closed file (jprotopopov).
 
 All (GUI):
 

include/wx/ffile.h

@@ -76,13 +76,13 @@ public:
   wxFileOffset Length() const;
 
   // simple accessors: note that Eof() and Error() may only be called if
-  // IsOpened()!
+  // IsOpened(). Otherwise they assert and return false.
     // is file opened?
   bool IsOpened() const { return m_fp != NULL; }
     // is end of file reached?
-  bool Eof() const { return feof(m_fp) != 0; }
+  bool Eof() const;
     // has an error occurred?
-  bool Error() const { return ferror(m_fp) != 0; }
+  bool Error() const;
     // get the file name
   const wxString& GetName() const { return m_name; }
     // type such as disk or pipe

interface/wx/ffile.h

@@ -89,10 +89,7 @@ public:
         Note that the behaviour of the file descriptor based class  wxFile is different as
         wxFile::Eof() will return @true here as soon as the last byte of the file has been read.
 
-        Also note that this method may only be called for opened files and may crash if
+        Also note that this method may only be called for opened files. Otherwise it asserts and returns false.
-        the file is not opened.
-
-        @todo THIS METHOD MAY CRASH? DOESN'T SOUND GOOD
 
         @see IsOpened()
     */
@@ -102,10 +99,7 @@ public:
         Returns @true if an error has occurred on this file, similar to the standard
         @c ferror() function.
 
-        Please note that this method may only be called for opened files and may crash
+        Please note that this method may only be called for opened files. Otherwise it asserts and returns false.
-        if the file is not opened.
-
-        @todo THIS METHOD MAY CRASH? DOESN'T SOUND GOOD
 
         @see IsOpened()
     */

src/common/ffile.cpp

@@ -281,4 +281,18 @@ wxFileOffset wxFFile::Length() const
     return wxInvalidOffset;
 }
 
+bool wxFFile::Eof() const
+{
+    wxCHECK_MSG( IsOpened(), false,
+                 wxT("wxFFile::Eof(): file is closed!") );
+    return feof(m_fp) != 0;
+}
+
+bool wxFFile::Error() const
+{
+    wxCHECK_MSG( IsOpened(), false,
+                 wxT("wxFFile::Error(): file is closed!") );
+    return ferror(m_fp) != 0;
+}
+
 #endif // wxUSE_FFILE

tests/file/filefn.cpp

@@ -48,6 +48,8 @@ private:
         CPPUNIT_TEST( RenameFile );
         CPPUNIT_TEST( ConcatenateFiles );
         CPPUNIT_TEST( GetCwd );
+        CPPUNIT_TEST( FileEof );
+        CPPUNIT_TEST( FileError );
     CPPUNIT_TEST_SUITE_END();
 
     void GetTempFolder();
@@ -60,6 +62,8 @@ private:
     void RenameFile();
     void ConcatenateFiles();
     void GetCwd();
+    void FileEof();
+    void FileError();
 
     // Helper methods
     void DoCreateFile(const wxString& filePath);
@@ -423,6 +427,61 @@ void FileFunctionsTestCase::GetCwd()
     CPPUNIT_ASSERT( !cwd.IsEmpty() );
 }
 
+void FileFunctionsTestCase::FileEof()
+{
+    const wxString filename(wxT("horse.bmp"));
+    const wxString msg = wxString::Format(wxT("File: %s"), filename.c_str());
+    const char *pUnitMsg = (const char*) msg.mb_str(wxConvUTF8);
+    wxFFile file(filename, wxT("r"));
+    // wxFFile::Eof must be false at start
+    CPPUNIT_ASSERT_MESSAGE( pUnitMsg, !file.Eof() );
+    CPPUNIT_ASSERT_MESSAGE( pUnitMsg, file.SeekEnd() );
+    // wxFFile::Eof returns true only after attempt to read last byte
+    char array[1];
+    CPPUNIT_ASSERT_MESSAGE( pUnitMsg, file.Read(array, 1) == 0 );
+    CPPUNIT_ASSERT_MESSAGE( pUnitMsg, file.Eof() );
+
+    CPPUNIT_ASSERT_MESSAGE( pUnitMsg, file.Close() );
+    // wxFFile::Eof after close should not cause crash but fail instead
+    bool failed = true;
+    try
+    {
+	file.Eof();
+        failed = false;
+    }
+    catch (...)
+    {
+    }
+    CPPUNIT_ASSERT_MESSAGE( pUnitMsg, failed );
+}
+
+void FileFunctionsTestCase::FileError()
+{
+    const wxString filename(wxT("horse.bmp"));
+    const wxString msg = wxString::Format(wxT("File: %s"), filename.c_str());
+    const char *pUnitMsg = (const char*) msg.mb_str(wxConvUTF8);
+    wxFFile file(filename, wxT("r"));
+    // wxFFile::Error must be false at start assuming file "horse.bmp" exists.
+    CPPUNIT_ASSERT_MESSAGE( pUnitMsg, !file.Error() );
+    // Attempt to write to file opened in readonly mode should cause error
+    CPPUNIT_ASSERT_MESSAGE( pUnitMsg, !file.Write(filename) );
+    CPPUNIT_ASSERT_MESSAGE( pUnitMsg, file.Error() );
+
+    CPPUNIT_ASSERT_MESSAGE( pUnitMsg, file.Close() );
+    // wxFFile::Error after close should not cause crash but fail instead
+    bool failed = true;
+    try
+    {
+        file.Error();
+        failed = false;
+    }
+    catch (...)
+    {
+    }
+    CPPUNIT_ASSERT_MESSAGE( pUnitMsg, failed );
+}
+
+
 /*
     TODO: other file functions to test: