Question

I am using MinGW GCC compiler on Windows 7. I am trying to compile source that contains the following code:

MEMORYSTATUSEX mem_stat;
mem_stat.dwLength = sizeof(memstat);
BOOL success = GlobalMemoryStatusEx(mem_stat);
ram_ptr = &(mem_stat->ullAvailPhys);

As I’m sure you can guess, this code simply gets the available memory using the MEMORYSTATUSEX struct returned by GlobalMemoryStatusEx.

When I try to compile, I get this error:

error: unknown type name 'MEMORYSTATUSEX'

I looked in winbase.h (in the MinGW installation include folder) and guess what I found?

#if (_WIN32_WINNT >= 0x0500)
typedef struct _MEMORYSTATUSEX {
    DWORD dwLength;
    DWORD dwMemoryLoad;
    DWORDLONG ullTotalPhys;
    DWORDLONG ullAvailPhys;
    DWORDLONG ullTotalPageFile;
    DWORDLONG ullAvailPageFile;
    DWORDLONG ullTotalVirtual;
    DWORDLONG ullAvailVirtual;
    DWORDLONG ullAvailExtendedVirtual;
} MEMORYSTATUSEX,*LPMEMORYSTATUSEX;
#endif

So it’s there. I’m guessing this has something to do with the precompiler if/endif, but I don’t how to fix that….

Also what’s even more bizzare is that if I use the MEMORYSTATUS struct instead, it works fine.

According to the MS docs, both have the same minimum client version requirement:

MEMORYSTATUSEX:
http://msdn.microsoft.com/en-us/library/windows/desktop/aa366589%28v=vs.85%29.aspx

MEMORYSTATUS:
http://msdn.microsoft.com/en-us/library/windows/desktop/aa366772%28v=vs.85%29.aspx

Is there some compiler flag I need to set? Or does anyone have any other solutions?

Thanks in advance for your help!

Answer 1

Apparently you have to define _WIN32_WINNT yourself either as a compiler flag or definition statement in one of your header/source files for this particular function to work properly.

Adding the #define _WIN32_WINNT 0x0500 will allow the code to compile normally.