const char * to char[]

[Allan Bruce]

Hi there,

I have a stuct which requires a char[64] (I cant change it as it is part of
the win32 api), but I have a const char * pointing to a string literal
declared as:

WCS->AppName = "Some Text";

Appname is a const char *. How do I convert from this to the char[64]
required for the struct?
Thanks
Allan

[J. J. Farrell]

"Allan Bruce" <al*****@TAKEAW AYf2s.com> wrote in message news:<bp******* ***@news.freedo m2surf.net>...

"Richard Bos" <rl*@hoekstra-uitgeverij.nl> wrote in message
news:3f******** ********@news.n l.net...

"Allan Bruce" <al*****@TAKEAW AYf2s.com> wrote:

The struct is declared as:
typedef struct _NOTIFYICONDATA {
char szTip[64];
} NOTIFYICONDATA, *PNOTIFYICONDAT A;

and my own struct is declared as:
typedef struct
{
const char *AppName;
} WinCoreStruct;

I initialise my struct with:
WCS->AppName = "WinCore Usage Program"; and I attempt to copy my AppName to NOTIFYICONDATA. szTip by:
NOTIFYICONDATA TrayIcon; // set structure strncpy(TrayIco n.szTip, mWCS->AppName, 64);

How have you declared WCS and mWCS? Do these actually point to the same
object? I can't find any problems with the code you've posted.

If you step through your code in a debugger, at what line does it
actually crash?

WCS and mWCS point to the same struct in memory, the code crashes on the
strncpy line. I thought my code was ok, could this be a microsoft issue?

It could be, but it's more likely to be some error in your code
that we don't yet have enough information to see. How are you
sure that mWCS points to the right place at the time of the error?
Its being wrong is the most likely cause of the problem.

Can you show a complete code sequence that shows how WCS and mWCS
get initialized, and everything that happens to them before the
call to strncpy()? A complete short program that shows the problem
would be best.

[Richard Bos]

gr******@the-junkyard.net (Charles Banas) wrote:

"Allan Bruce" <al*****@TAKEAW AYf2s.com> wrote in message news:<bp******* **@news.freedom 2surf.net>...

and I attempt to copy my AppName to NOTIFYICONDATA. szTip by:
NOTIFYICONDATA TrayIcon; // set structure
strncpy(TrayIco n.szTip, mWCS->AppName, 64); // tooltip text to display

Be careful. You happen to know that your string fits now, but consider
what would happen if AppName were exactly 64 characters long, not
including the terminating null character.
call me naiive, but isn't it possible that the memory beyond the
string AppName points to could be code memory?
What has that got to do with it?
strncpy(TrayIco n.szTip, mWCS->AppName, 22);

You are confused about the behaviour of strncpy(), I suspect. It does
_not_ copy exactly N bytes - if it did, you might as well use memcpy().
What it does is copy up to either the end of the string, or N bytes,
whichever comes first. And then, superfluously, pads the rest with null
characters.

Richard