Increase DWORD by one?

[FastLife]

hello you

 

i want to increase a dword value by 1.

So using c++ to get a value of a pointer, and using inline asm to increase this value by one. so far it works.

 

now i want to remove that inline asm, and increasing the value by one in c++ itself. but that doesn't work because somehow it increase the value by 4 instead of 1.

 

 

working with inline asm

DWORD *value = (DWORD*)(VAaddress);

__asm{

	inc value

}

not working in fully c++

DWORD *value = (DWORD*)(VAaddress);

value++;

and ideas?

Edited November 1, 2014 by FastLife

[evlncrn8]

value[0] +=1;

perhaps...

considering value is a pointer...

[ragdog]

http://www.tutorialspoint.com/cplusplus/cpp_increment_decrement_operators.htm

 

I hope it help

Edited November 1, 2014 by ragdog

[FastLife]

thanks for helping but unfortunately it didn't work.

 

this

Pointer *pointerOfAddress = (Pointer*)(VAaddress);

pointerOfAddress[0] += 1;

will result in the error Size of the type 'void' is unknown or zero.

[Deathway]

Try this

 

*value += 1;

[FastLife]

thanks deathway, this time no errors. however, it increments the value of 4, instead of one, like before.

probably because a dword is 4 bytes so thats why it adds 4. but don't know how to add just 1 byte.

[metr0]

Yes. Increments use the factor sizeof(source_type), so it increments by sizeof(DWORD), which equals 4. You can use a cast to make your intent clear by casting to unsigned char*. Eventually you'll want to have a macro for adding values to pointers..

 

Edit: Above assumes one wants to increment the pointer by one, not the value itself.

Edited November 3, 2014 by metr0

[atom0s]

You can just do:

*value += 1;

For example:

// Create some fake memory to store our value..

auto lpAddr = ::VirtualAlloc(NULL, 4, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
// Set the first dword in the allocated memory to 4..

*(DWORD*)lpAddr = 4;
// Create pointer to the address..

DWORD* value = (DWORD*)lpAddr;
// Read the current value.. (Value is currently 4.)

DWORD currValue = *value;
// Increment the value by 1..

*value += 1;
// Read the new value..

DWORD newValue = *value; (Value is now 5.)

Also if you want to just use ++, then with Visual Studio, at least, you must surround the pointer in parenthesis first before you attempt to alter it to ensure the actual object being altered is the pointed value, and not the pointer address. Like this:

(*value)++;

Edited November 2, 2014 by atom0s

[FastLife]

Awesome atm0s, it works now! Thank you very much.

also thanks to metr0 for the information and others who replied here, thank you guys!