GlobalAlloc说明

Question

(char*)GlobalAlloc(GPTR, len + 1);

This is the line of code in question, which I'm using from a tutorial. I'm reading from an EDITTEXT . I'd mostly like to know where GPTR came from, and what it's for. It hasn't been defined anywhere else in the code.

I've got a basic understanding of the rest of the line, but MSDN 's explanation isn't quite clear. They say this:

HGLOBAL WINAPI GlobalAlloc(
  __in  UINT uFlags,
  __in  SIZE_T dwBytes
);

Could someone explain in plain English where GPTR is from, what it's for, and how it relates to __in UINT uFlags ? I know it's an unsigned int but then the knowing stops.

Thanks in advance.

Answer 1

GPTR is athe combination of GMEM_FIXED and GMEM_ZEROINIT(OR).

uFlags
The memory allocation attributes. If zero is specified, the default is GMEM_FIXED. This parameter can be one or more of the following values, except for the incompatible combinations that are specifically noted.

Value Meaning
GHND 0x0042 Combines GMEM_MOVEABLE and GMEM_ZEROINIT.
GMEM_FIXED 0x0000 Allocates fixed memory. The return value is a pointer.
GMEM_MOVEABLE 0x0002 Allocates movable memory. Memory blocks are never moved in physical memory, but they can be moved within the default heap. This value cannot be combined with GMEM_FIXED.
GMEM_ZEROINIT 0x0040 Initializes memory contents to zero.
GPTR 0x0040 Combines GMEM FIXED and GMEM_ZEROINIT.

Answer 2

Refer here

GPTR 0x0040 Combines GMEM_FIXED and GMEM_ZEROINIT.

As you can see, it is just a bit pattern (0x0040) and can be combined with other permissible flags