WM_CREATE and BOOLs

Got a couple more questions:

a) The lParam of the WM_CREATE message is, according to Microsoft, "Pointer to a CREATESTRUCT structure that contains information about the window being created." However when I try to do things like lParam->lpCreateParams, I get the compiler error "base operand of `->' is not a pointer".

b) What is the BOOL type? I know that the "bool" type (lowercase) is a type in Standard C++ which can be "true" or "false". When I used to do C, we used to define things like:

Code:

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typedef enum{FALSE, TRUE} BOOL;

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and I guessed that this was what the "bool" type was. But now we get this "BOOL" type (uppercase) and I find that the GetMessage function (which returns a BOOL) can return -1 as a value! Is a BOOL just a signed int? In which case it is taking up way too much memory for a boolean variable which should take only one byte.

1. You need to cast it to a CREATESTRUCT pointer first.

Code:

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CREATESTRUCT* pcs = (CREATESTRUCT*)lParam;
pcs->lpCreateParams /* ... */

// or

((CREATESTRUCT*)lParam)->lpCreateParams /* ... */

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2. Exactly.

Quote:

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Originally Posted by kidburla

and I guessed that this was what the "bool" type was. But now we get this "BOOL" type (uppercase) and I find that the GetMessage function (which returns a BOOL) can return -1 as a value! Is a BOOL just a signed int? In which case it is taking up way too much memory for a boolean variable which should take only one byte.

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I've heard this before, someone else had said that it is cheaper for a 32 bit processor to access an 32 bit int value rather than a byte which requires moving into ax and then isolate the low word twice, I think the bool in C++ is implemented as a 32 bit int as well.

bool in C++ is one byte or larger, there's no standard value.

BOOL in windows is an int, so it will be 16/32/64 bits depending on what int is.

As an aside, a one-byte variable can also hold -1 you know.