dev-cpp-users

[Dev-C++] file handle error

[Noorez K. <lor...@ho...>]

The open file function of my program appears to be crashing at the line I 
marked, when I run the debugger. There might be some other problem causing 
it. The function is below:

#include "SML.h"

// Function called from WindowProcedure to open text
void OpenText(HWND main, HWND hEdit)
{
  ifstream openTextFile; // Handle to file

  // Filter files visible in the open dialog box
  char* filter = "Text Files (*.txt)\0*.txt\0All Files (*.*)\0*.*\0\0";

  std::string inLine;
  char* toEditControl;

  int nLength;

  // Init the properties of the open dialog box
  getOFNproperties(main, &dialogProperties, currentFileName, filter);

  // Show the dialog and get the information
  if( !GetOpenFileName(&dialogProperties) )
  {
    return; // Return if user cancels
  }

  openTextFile.open(currentFileName);
  SetDlgItemText(main, IDC_MAIN_EDIT, ""); // Clear the edit contro

  int cntr = 1;

  // Loop unitl the end of file is reached
  while( !openTextFile.eof() && !openTextFile.fail()  )
  {
    nLength = GetWindowTextLength(GetDlgItem(main, IDC_MAIN_EDIT));
    getline(openTextFile,inLine);
    toEditControl = (char*)inLine.c_str();

     //A new line must have a "\r\n" so test for both
    if( toEditControl[ strlen(toEditControl) -1 ] != '\r' )
    {
      strcat(toEditControl,"\r");
    }
    if( inLine[ strlen(toEditControl) -1] != '\n' )
    {
      strcat(toEditControl,"\n");
    }

    // And the message onto the edit control
    SendMessage( GetDlgItem(main, IDC_MAIN_EDIT), EM_SETSEL, 
(WPARAM)nLength,
                 (LPARAM)nLength );

    SendMessage( GetDlgItem(main, IDC_MAIN_EDIT), EM_REPLACESEL, 
(WPARAM)FALSE,
                 (LPARAM)toEditControl );
  }

  untitled = false;
  edited = false;
  openTextFile.close();
  return;
}

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Re: [Dev-C++] file handle error

[Per W. <pw...@ia...>]

I don't know what line you marked.

However, PLEASE try and use std::string and not immediately change over to
C arrays. C character arrays are perfectly fine to use WHEN YOU KNOW HOW
TO USE THEM.

Now you read a line of text from the edit control into a std::string
object.

Then you immediately ask for a pointer to a zero-terminated string using
the method c_str() and type cast into a writeable pointer:

Finally, you try to concatenate more chanracters to the c string...

Exactly HOW do you think string:c_str() should now about your intentions
to concatenate more characters and reserve room for these extra
characters? You should do ALL manipulation on the std::string.

You typecast c_str() to (char*) just to be able to play with the c string.
However, the c string is NOT meant to be played with. It is a read-only
string!

/Per W

On Mon, 11 Jul 2005, Noorez Kassam wrote:

> The open file function of my program appears to be crashing at the line I
> marked, when I run the debugger. There might be some other problem causing
> it. The function is below:
>
> #include "SML.h"
>
> // Function called from WindowProcedure to open text
> void OpenText(HWND main, HWND hEdit)
> {
>   ifstream openTextFile; // Handle to file
>
>   // Filter files visible in the open dialog box
>   char* filter = "Text Files (*.txt)\0*.txt\0All Files (*.*)\0*.*\0\0";
>
>   std::string inLine;
>   char* toEditControl;
>
>   int nLength;
>
>   // Init the properties of the open dialog box
>   getOFNproperties(main, &dialogProperties, currentFileName, filter);
>
>   // Show the dialog and get the information
>   if( !GetOpenFileName(&dialogProperties) )
>   {
>     return; // Return if user cancels
>   }
>
>   openTextFile.open(currentFileName);
>   SetDlgItemText(main, IDC_MAIN_EDIT, ""); // Clear the edit contro
>
>   int cntr = 1;
>
>   // Loop unitl the end of file is reached
>   while( !openTextFile.eof() && !openTextFile.fail()  )
>   {
>     nLength = GetWindowTextLength(GetDlgItem(main, IDC_MAIN_EDIT));
>     getline(openTextFile,inLine);
>     toEditControl = (char*)inLine.c_str();
>
>      //A new line must have a "\r\n" so test for both
>     if( toEditControl[ strlen(toEditControl) -1 ] != '\r' )
>     {
>       strcat(toEditControl,"\r");
>     }
>     if( inLine[ strlen(toEditControl) -1] != '\n' )
>     {
>       strcat(toEditControl,"\n");
>     }
>
>     // And the message onto the edit control
>     SendMessage( GetDlgItem(main, IDC_MAIN_EDIT), EM_SETSEL,
> (WPARAM)nLength,
>                  (LPARAM)nLength );
>
>     SendMessage( GetDlgItem(main, IDC_MAIN_EDIT), EM_REPLACESEL,
> (WPARAM)FALSE,
>                  (LPARAM)toEditControl );
>   }
>
>   untitled = false;
>   edited = false;
>   openTextFile.close();
>   return;
> }