How to update the value of LPCTSTR lpSubKey in RegOpenKeyEx()?

**ArunS** · 03-21-2012

I just want to open a key in a registry(Windows XP) using RegOpenKeyEx() function which takes the second argument as path of the registry key. The second argument type is LPCTSTR (means pointer to a Const Char).

Example of the Path:
"HKEY_LOCAL_MACHINE\\SYSTEM\\CurrentControlSet\\.. .\\...\\..."

here I know about the path till the \\CurrentControlSet\\... at starting. There after i will came to know the exact path at runtime.
How can i modified that?

Main problem is we have to pass the second argument in RegOpenKeyEx() function as LPCTSTR.

**ssharish2005** · 03-21-2012

I quite dont understand. So you dont know the part of the register, but you partially know it.

Well cant you just construct the path at the run time, once you get to know the registry? Its would rather be pretty easy to construct a string. And then type cast it to LPCTSTR?

ssharish

**ArunS** · 03-21-2012

Originally Posted by ssharish2005

I quite dont understand. So you dont know the part of the register, but you partially know it.

Well cant you just construct the path at the run time, once you get to know the registry? Its would rather be pretty easy to construct a string. And then type cast it to LPCTSTR?

ssharish

I already try that typecasting, but it doesn't work.
because while in the actual scenario, calling of this the function could seems like,

Code:

RegOpenKeyEx(HKEY_LOCAL_MACHINE,
		TEXT("SYSTEM\\CurrentControlSet\\Enum\\USB\\Vid_0458&Pid_9856\\7654321"),
		0,
		KEY_READ,
		&hKey);

The above function calls executes fine and returns 0.

In my actual scenario, We have to do the type casting on the second parameter TEXT("....").
so what i did,
get the path into "ptr" pointer in the run time, and did the typecasting as

Code:

RegOpenKeyEx(HKEY_LOCAL_MACHINE,
		(LPCWSTR)ptr,
		0,
		KEY_READ,
		&hKey);

but this function gets failed and returns 2.

Any suggestions are welcome!!

**Salem** · 03-21-2012

Then you need to make sure ptr is pointing to a wide string.
If it's just a narrow string, then simply casting your way out of trouble just to make the compiler STFU just doesn't work.

Casting a pointer doesn't magically make what it points to valid.

Think first, and then cast only if it's the right thing to do. Applying it all over the place as some band-aid sticking plaster isn't the way to go.

**oogabooga** · 03-21-2012

Why don't you turn off unicode? (In project properties, set character set to "not set".)

Or explicitly use the non-unicode version of the function RegOpenKeyExA? (Note the A at the end.)

Or convert your string to unicode like this?

Code:

#define WSTR_SIZE 256
LPWSTR wstr[WSTR_SIZE];

// with a C library function
mbstowcs(wstr, str, WSTR_SIZE);

// with a Windows function
MultiByteToWideChar(CP_ACP, 0, str, strlen(str), wstr, WSTR_SIZE);

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How to update the value of LPCTSTR lpSubKey in RegOpenKeyEx()?

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