strcat - strange behavior

[Lilith]

I'm working on a simple piece of code under VC++ 6.0. I've got a char
Buffer array into which I copy the contents of an MFC control. The
string is properly nul terminated. I use strcat (Buffer, "\r\n") to
append a carriage return\line feed to the string before outputting it
to a display where I can monitor what's being exchanged with another
service. But after the strcat the string in Buffer is terminated, not
with \r\n but with a \n and NO nul terminator. The carriage return is
dropped completely.

If this was output for a text file I'd think it was an expected
conversion. But all of this is still in memory.

TIA,
Lilith

[Victor Bazarov]

Lilith wrote:

I'm working on a simple piece of code under VC++ 6.0. I've got a char
Buffer array into which I copy the contents of an MFC control.
You know that MFC is off-topic, right? Just checking. I understand that
you're not asking about MFC per se.
The
string is properly nul terminated. I use strcat (Buffer, "\r\n") to
append a carriage return\line feed to the string before outputting it
to a display
Outputting a string to a display is not defined in C++, you know that,
right? There is no such thing as "display" in C++.
where I can monitor what's being exchanged with another
service. But after the strcat the string in Buffer is terminated, not
with \r\n but with a \n and NO nul terminator.
I think this is covered in the FAQ. See 5.8.
The carriage return is
dropped completely.

If this was output for a text file I'd think it was an expected
conversion. But all of this is still in memory.

I'll believe you when I see the code.

V
--
Please remove capital As from my address when replying by mail

[Lilith]

On Mon, 27 Feb 2006 17:08:53 -0500, Victor Bazarov
<v.********@com Acast.net> wrote:

Lilith wrote:

I'm working on a simple piece of code under VC++ 6.0. I've got a char
Buffer array into which I copy the contents of an MFC control.

You know that MFC is off-topic, right? Just checking. I understand that
you're not asking about MFC per se.
Even when I'm striving for completeness?
The
string is properly nul terminated. I use strcat (Buffer, "\r\n") to
append a carriage return\line feed to the string before outputting it
to a display Outputting a string to a display is not defined in C++, you know that,
right? There is no such thing as "display" in C++.
Yes, and once again, the purpose was completeness. I wanted it
understood why I was appending the CR\LF combination.
where I can monitor what's being exchanged with another
service. But after the strcat the string in Buffer is terminated, not
with \r\n but with a \n and NO nul terminator. I think this is covered in the FAQ. See 5.8. The carriage return is
dropped completely. If this was output for a text file I'd think it was an expected
conversion. But all of this is still in memory.

I'll believe you when I see the code.
strcpy (Buffer, "MAIL FROM: ");
m_From.GetWindo wText(Text, 512); // sorry if this is MFC
strcat (Buffer, Text); // up to this point the string is nul
// terminated

// Buffer is passed to a function but is still null
// terminated following the call

strcat(Buffer, "\r\n"); // after this operation the
// string is LF terminated with no
// nul
V

--
Lilith

[roberts.noah]

Lilith wrote:

On Mon, 27 Feb 2006 17:08:53 -0500, Victor Bazarov
<v.********@com Acast.net> wrote:

Lilith wrote:

I'm working on a simple piece of code under VC++ 6.0. I've got a char
Buffer array into which I copy the contents of an MFC control.

You know that MFC is off-topic, right? Just checking. I understand that
you're not asking about MFC per se.

Even when I'm striving for completeness?
The
string is properly nul terminated. I use strcat (Buffer, "\r\n") to
append a carriage return\line feed to the string before outputting it
to a display

Outputting a string to a display is not defined in C++, you know that,
right? There is no such thing as "display" in C++.

Yes, and once again, the purpose was completeness. I wanted it
understood why I was appending the CR\LF combination.
where I can monitor what's being exchanged with another
service. But after the strcat the string in Buffer is terminated, not
with \r\n but with a \n and NO nul terminator.

I think this is covered in the FAQ. See 5.8.

The carriage return is
dropped completely. If this was output for a text file I'd think it was an expected
conversion. But all of this is still in memory.

I'll believe you when I see the code.

strcpy (Buffer, "MAIL FROM: ");
m_From.GetWindo wText(Text, 512); // sorry if this is MFC
strcat (Buffer, Text); // up to this point the string is nul
// terminated

// Buffer is passed to a function but is still null
// terminated following the call

strcat(Buffer, "\r\n"); // after this operation the
// string is LF terminated with no
// nul

What is strlen(Buffer) vs. sizeof(Buffer)?

[Lilith]

On 27 Feb 2006 14:43:18 -0800, ro**********@gm ail.com wrote:

Lilith wrote:

On Mon, 27 Feb 2006 17:08:53 -0500, Victor Bazarov
<v.********@com Acast.net> wrote:

>Lilith wrote:
>> I'm working on a simple piece of code under VC++ 6.0. I've got a char
>> Buffer array into which I copy the contents of an MFC control.

>You know that MFC is off-topic, right? Just checking. I understand that
>you're not asking about MFC per se.

Even when I'm striving for completeness?

> > The
>> string is properly nul terminated. I use strcat (Buffer, "\r\n") to
>> append a carriage return\line feed to the string before outputting it
>> to a display

>Outputting a string to a display is not defined in C++, you know that,
>right? There is no such thing as "display" in C++.

Yes, and once again, the purpose was completeness. I wanted it
understood why I was appending the CR\LF combination.

> > where I can monitor what's being exchanged with another
>> service. But after the strcat the string in Buffer is terminated, not
>> with \r\n but with a \n and NO nul terminator.

>I think this is covered in the FAQ. See 5.8.

> > The carriage return is
>> dropped completely.

>> If this was output for a text file I'd think it was an expected
>> conversion. But all of this is still in memory.

>I'll believe you when I see the code.

strcpy (Buffer, "MAIL FROM: ");
m_From.GetWindo wText(Text, 512); // sorry if this is MFC
strcat (Buffer, Text); // up to this point the string is nul
// terminated

// Buffer is passed to a function but is still null
// terminated following the call

strcat(Buffer, "\r\n"); // after this operation the
// string is LF terminated with no
// nul

What is strlen(Buffer) vs. sizeof(Buffer)?

sizeof(Buffer) = 512
strlen(Buffer) := 50

Lots of room.

--
Lilith

[Kaz Kylheku]

Victor Bazarov wrote:

Outputting a string to a display is not defined in C++, you know that,
right? There is no such thing as "display" in C++.

There doesn't have to be, because that's covered in the C standard.

Section "5.2.2 Character display semantics" in 9899:1999.

:)

[roberts.noah]

Lilith wrote:

What is strlen(Buffer) vs. sizeof(Buffer)?

sizeof(Buffer) = 512
strlen(Buffer) := 50

Lots of room.

Skirt the issue then, set buffer to all 0 before processing. Then if
it fails something is modifying it in a way you are not expecting and
you can look for it.

[Frank Schmidt]

<ro**********@g mail.com> schrieb im Newsbeitrag
news:11******** **************@ i40g2000cwc.goo glegroups.com.. .

Lilith wrote:

>What is strlen(Buffer) vs. sizeof(Buffer)?

sizeof(Buffer) = 512
strlen(Buffer) := 50

Lots of room.

Skirt the issue then, set buffer to all 0 before processing. Then if
it fails something is modifying it in a way you are not expecting and
you can look for it.

does a strlen of 50 not kinda indicates the real length and that there is a
0 and a wrong "DISPLAY"?

[Kaz Kylheku]

Lilith wrote:

strcpy (Buffer, "MAIL FROM: ");
m_From.GetWindo wText(Text, 512); // sorry if this is MFC
strcat (Buffer, Text); // up to this point the string is nul
// terminated
Neither strcpy() nor strcat() have any mechanism to guard against
storing more characters than the destination array can hold.
// Buffer is passed to a function but is still null
// terminated following the call

strcat(Buffer, "\r\n"); // after this operation the
// string is LF terminated with no
// nul

How do you know? Are you by chance relying on the variable inspection
window of your debugger? That Microsoft thing has certain issues when
it comes to displaying strings. It cuts off strings that are too long,
and I think it basically just stuffs the text into its own control, so
that \r\n just becomes a line break. I haven't used it in a long time,
so I can't quite remember. If you want to be sure what's in that
character array, you should convert it yourself to printable form and
dump it to a debug trace function.

Oh, you do know that C++ has a string class, right?

Moreover, you do know that MFC has a CString class?

Moreover, you do know that the control you are using has a
GetWindowText() overload that will put data into a CString object?

void CWnd::GetWindow Text(CString& rString) const;

Why are you messing around with strcat instead of using the string type
provided by the framework in which you are making the GUI?

Idiot!

[Victor Bazarov]

Kaz Kylheku wrote:

Victor Bazarov wrote:

Outputting a string to a display is not defined in C++, you know that,
right? There is no such thing as "display" in C++.

There doesn't have to be, because that's covered in the C standard.

Section "5.2.2 Character display semantics" in 9899:1999.

:)

How is that relevant? AFAIK, C++ Standard only refers to 9899:1990. :)