strcat problem

  • Thread starter Thread starter arssa2020
  • Start date Start date
A

arssa2020

hello all,

ms visual studio 2003,
i need to read serial bytes (one byte at a time) from serial port, and
the catenate it to a char* (cannot use strings)
strcat require that the 2nd parameters (the src)to be of type
const char*.
so i cast the (char byte) to be a (char*)

i have the following code
char byte;
char s[128]
.....
//read serial data from serial port
ReadFile (hPort, &byte, 1, &dwBytesTransferred, 0);
....
if(byte !=0x0D) //CR
{
//append the received byte to the string s
strcat(s,(char*)byte)
}

//it gives me access violation
"Unhandled exception at 0x00420601 in Test.exe: 0xC0000005: Access
violation reading location 0x00000047."

how can i go around it?
i cannot use string class members..
thanks
 
hello all,

ms visual studio 2003,
i need to read serial bytes (one byte at a time) from serial port, and
the catenate it to a char* (cannot use strings)
strcat require that the 2nd parameters (the src)to be of type
const char*.
so i cast the (char byte) to be a (char*)
Click to expand...

No, you most certainly cannot.
i have the following code
char byte;
char s[128]
....
//read serial data from serial port
ReadFile (hPort, &byte, 1, &dwBytesTransferred, 0);
...
if(byte !=0x0D) //CR
{
//append the received byte to the string s
strcat(s,(char*)byte)
}

//it gives me access violation
"Unhandled exception at 0x00420601 in Test.exe: 0xC0000005: Access
violation reading location 0x00000047."
Click to expand...

Naturally. You're trying to access an address on 0x00000000 .. 0x000000ff,
all of which are in the protected page at the botttom of the address range.
how can i go around it?
i cannot use string class members..
Click to expand...

Why not?

Anyway, try something like this:

<code>
char s[128] = {0};
int length = 0;
.....
//read serial data from serial port
ReadFile (hPort, &s[length], 1, &dwBytesTransferred, 0);
....
if(byte !=0x0D) //CR
{
length++;
}
</code>

using strcat to append a single byte is quite a waste of effort when you can
just read the byte into the right place to start with.

Be sure to protect against buffer overflow (i.e. make sure length is always
<=127 and handle appropriately if it tries to go out of bounds).

-cd
 
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