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

[Andreas Kahari]

In article <bp*********@ne ws.freedom2surf .net>, Allan Bruce wrote:

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?

Using strncpy():
#include <string.h>

/* ... later ... */

strncpy(somestr uct.thefield, WCS->AppName, 64);

--
Andreas Kähäri

[Richard Bos]

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

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?

I assume the struct actually contains the char array, rather than a
pointer? That is, it's

struct foo {
char bar[64];
/* other members... */
} qux;

rather than

struct foo {
char *bar; /* Must point to 64 bytes of memory */
/* other members... */
} qux;

If so, you can simply strcpy(qux.bar, Appname).

If not, post the definition of the struct, the declaration of your
current struct object, and the code in which you use the struct.

Richard

[Allan Bruce]

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

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

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?
I assume the struct actually contains the char array, rather than a
pointer? That is, it's

struct foo {
char bar[64];
/* other members... */
} qux;

This is the case, but it doesnt work - I tried strncpy() - my code is below

If so, you can simply strcpy(qux.bar, Appname).

If not, post the definition of the struct, the declaration of your
current struct object, and the code in which you use the struct.

Richard

The struct is declared as:
typedef struct _NOTIFYICONDATA {
DWORD cbSize;
HWND hWnd;
UINT uID;
UINT uFlags;
UINT uCallbackMessag e;
HICON hIcon;
char szTip[64];
} NOTIFYICONDATA, *PNOTIFYICONDAT A;

and my own struct is declared as:
typedef struct
{
UINT Xres;
UINT Yres;
const char *AppName;
WNDPROC WndProc;
} 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); // tooltip text to display

Where am I going wrong?
Thanks
Allan

[Allan Bruce]

I forgot to mention - the error I get is an access violation and my program
just crashes - no compiler error or warning.
Thanks
Allan

[Richard Bos]

"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); // tooltip text to display

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?

Richard

[Allan Bruce]

"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); // tooltip text to

display
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?

Richard

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?
Thanks
Allan

[Charles Banas]

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

"Richard Bos" <rl*@hoekstra-uitgeverij.nl> wrote in message
news:3f******** ********@news.n l.net... <snip> The struct is declared as:
typedef struct _NOTIFYICONDATA {
DWORD cbSize;
HWND hWnd;
UINT uID;
UINT uFlags;
UINT uCallbackMessag e;
HICON hIcon;
char szTip[64];
} NOTIFYICONDATA, *PNOTIFYICONDAT A;

and my own struct is declared as:
typedef struct
{
UINT Xres;
UINT Yres;
const char *AppName;
WNDPROC WndProc;
} 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); // tooltip text to display

Where am I going wrong?
Thanks
Allan

call me naiive, but isn't it possible that the memory beyond the
string AppName points to could be code memory?

have you tried just strcpy() instead of strncpy()?

or have you tried this instead? :

strncpy(TrayIco n.szTip, mWCS->AppName, 22);

seems to me that'd be the safer way to go.

[Allan Bruce]

"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); // tooltip text to

display
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?

Richard

I found the problem - it turns out my mWCS was becoming invalid through a
memory trash elsewhere.
Thanks for the help
Allan

[J. J. Farrell]

gr******@the-junkyard.net (Charles Banas) wrote in message news:<a7******* *************** ***@posting.goo gle.com>...

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

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

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

and my own struct is declared as:
typedef struct
{
<snip>
const char *AppName;
WNDPROC WndProc;
} 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); // tooltip text to display

Where am I going wrong?

call me naiive, but isn't it possible that the memory beyond the
string AppName points to could be code memory?

Yes.
have you tried just strcpy() instead of strncpy()?

or have you tried this instead? :

strncpy(TrayIco n.szTip, mWCS->AppName, 22);

seems to me that'd be the safer way to go.

Why? If he can't rely on strncpy() from a major implementation
working properly, he might as well give up.