Assigning values via pointers in C/C++? (Visual Studio.NET 2003)

[Usenet User]

I am using Visual Studio.NET 2003, and to my surprise, the below code
in a simple console application does not work for me:

char *str = "hello!";
*str = 'H'; <-- error
str[0] = 'H'; <-- error

The above code compiles just fine, but I am getting runtime errors.
If managed extensions are used, I'm getting "Objest reference is not
set to an object." If I disable managed extensions, I get "Access
violation" errors.

Any suggestions?

TIA!

[=?Utf-8?B?Sm9obiBIZW5zbGV5?=]

The string "Hello!" is a const value that is located in a read-only area of
memory. When you try to change the first character of the string with *str =
'H' and str[0]=h you are attempting to overwrite read-only memory and that is
why you are getting an exception.

Use something like this if you want to be able to overwrite your string.

char *tmp[] = "Hello!"
char *str = tmp;
*str = 'H';
str[0] = 'H';

--
John Hensley
www.resqware.com
"Usenet User" wrote:

I am using Visual Studio.NET 2003, and to my surprise, the below code
in a simple console application does not work for me:

char *str = "hello!";
*str = 'H'; <-- error
str[0] = 'H'; <-- error

The above code compiles just fine, but I am getting runtime errors.
If managed extensions are used, I'm getting "Objest reference is not
set to an object." If I disable managed extensions, I get "Access
violation" errors.

Any suggestions?

TIA!

[Larry Smith]

>I am using Visual Studio.NET 2003, and to my surprise, the below code

in a simple console application does not work for me:

char *str = "hello!";
*str = 'H'; <-- error
str[0] = 'H'; <-- error

The above code compiles just fine, but I am getting runtime errors.
If managed extensions are used, I'm getting "Objest reference is not
set to an object." If I disable managed extensions, I get "Access
violation" errors.

You can't assign to a string literal. It's type is "const char[]". Your
declaration should therefore be:

const char *str = "hello!";

The "const" can be omitted for backwards compatibility with C but it's still
illegal to write to this space. You should therefore specify the "const". If
you wnat to modify it then copy it instead:

char str[] = "hello!";

[=?Utf-8?B?Sm9obiBIZW5zbGV5?=]

char *tmp[] = "Hello!"

should have been

char tmp[] = "Hello!"
--
John Hensley
www.resqware.com
"John Hensley" wrote:

The string "Hello!" is a const value that is located in a read-only area of
memory. When you try to change the first character of the string with *str =
'H' and str[0]=h you are attempting to overwrite read-only memory and that is
why you are getting an exception.

Use something like this if you want to be able to overwrite your string.

char *tmp[] = "Hello!"
char *str = tmp;
*str = 'H';
str[0] = 'H';

--
John Hensley
www.resqware.com
"Usenet User" wrote:

I am using Visual Studio.NET 2003, and to my surprise, the below code
in a simple console application does not work for me:

char *str = "hello!";
*str = 'H'; <-- error
str[0] = 'H'; <-- error

The above code compiles just fine, but I am getting runtime errors.
If managed extensions are used, I'm getting "Objest reference is not
set to an object." If I disable managed extensions, I get "Access
violation" errors.

Any suggestions?

TIA!

[=?Utf-8?B?Sm9obiBIZW5zbGV5?=]

The line:
char *tmp[] = "Hello!"
should be:
char tmp[] = "Hello!"

--
John Hensley
www.resqware.com
"John Hensley" wrote:

The string "Hello!" is a const value that is located in a read-only area of
memory. When you try to change the first character of the string with *str =
'H' and str[0]=h you are attempting to overwrite read-only memory and that is
why you are getting an exception.

Use something like this if you want to be able to overwrite your string.

char *tmp[] = "Hello!"
char *str = tmp;
*str = 'H';
str[0] = 'H';

--
John Hensley
www.resqware.com
"Usenet User" wrote:

I am using Visual Studio.NET 2003, and to my surprise, the below code
in a simple console application does not work for me:

char *str = "hello!";
*str = 'H'; <-- error
str[0] = 'H'; <-- error

The above code compiles just fine, but I am getting runtime errors.
If managed extensions are used, I'm getting "Objest reference is not
set to an object." If I disable managed extensions, I get "Access
violation" errors.

Any suggestions?

TIA!

[Larry Smith]

char *tmp[] = "Hello!"

>
should have been

char tmp[] = "Hello!"

You don't need "tmp". This will do fine:

char str[] = "Hello!";
*str = 'H';
str[0] = 'H';

[David Wilkinson]

Usenet User wrote:

I am using Visual Studio.NET 2003, and to my surprise, the below code
in a simple console application does not work for me:

char *str = "hello!";
*str = 'H'; <-- error
str[0] = 'H'; <-- error

The above code compiles just fine, but I am getting runtime errors.
If managed extensions are used, I'm getting "Objest reference is not
set to an object." If I disable managed extensions, I get "Access
violation" errors.

Any suggestions?

UU:

When you write

char *str = "hello!";

the string is (or at least may be) in read-only memory. That is why you
get a runtime error when you try to change it. In fact in C++ you should
write

const char *str = "hello!";

and then

*str = 'H';

will fail to compile. The form

char *str = "hello!";

is only allowed to provide compatibility with legacy C code. Don't do it!

--
David Wilkinson
Visual C++ MVP

[Usenet User]

On Fri, 9 Nov 2007 16:31:40 -0500, "Larry Smith" <no_spam@_nospa m.com>
wrote:

>char *tmp[] = "Hello!"

should have been

char tmp[] = "Hello!"

You don't need "tmp". This will do fine:

char str[] = "Hello!";
*str = 'H';
str[0] = 'H';

Doh!

Thanks , everyone! I suspected something like this was going on...

-UU