Difference between char * and LPSTR in windows

问题:

I apologise if it is a basic or silly question. What is the difference between char* and LPSTR. where the sizeof both gives 4 bytes in my compiler. Can someone explain me in detail. thanks..

回答1:

LPSTR is a Windows type, meant to be be the same regardless of what platform you were compiling on. It's a long pointer to a string.

Back in the days of segmented architecture (the old 64K segments, not the newer selector-based segmented memory), where you had tiny, small, medium, large and huge memory models, it was important that the Windows type was always the same, regardless of what type of pointer char * was.

So, if you complied with different compilers where the underlying types were different, the windows.h header file would define LPSTR to compensate for that.

For example, Borland C may have had a sixteen-bit char * and LPSTR may have had to be defined as far char * for it. In a compiler where char * was already a long/far pointer, LPSTR would have just used that instead.

Nowadays, with 32+ bit flat models, there is probably no real need for such shenanigans, though it may still happen with things like thunking between 64-bit and 32-bit code. Still, the types defined back there are still with us and still very much in use.

回答2:

Basically, the LP* pointers were to indicate to use a 32 bit pointer on 16 bit versions of Windows:

From WikiBooks

The letters "LP" or the prefix "lp" stands for "Long Pointer", which is exactly the same as a regular pointer on 32 bit machines. LP data objects are simply legacy objects that were carried over from Windows 3.1 or later, when pointers and long pointers needed to be differentiated. On modern 32-bit systems, these prefixes can be used interchangeably.

回答3:

The difference is burried in the depths of time. LPSTR stands for "long pointer to string". Back before 32-bit processors, pointers to memory that might be in a different segment of memory (think, a long way away in memory), needed extra space to store.

On 32-bit (and later) processors, they're exactly the same thing. Microsoft uses LPSTR solely for historic reasons.