Make physmem.h work on old Windows versions.

Thanks to Hongbo Ni for the original patch.

diff --git a/src/common/physmem.h b/src/common/physmem.h
index 7075bc5..acf03c7 100644 (file)
--- a/src/common/physmem.h
+++ b/src/common/physmem.h
@@ -81,10 +81,33 @@ physmem(void)
                ret = (uint64_t)(si.totalram) * si.mem_unit;
 
 #elif defined(_WIN32)
-       MEMORYSTATUSEX meminfo;
-       meminfo.dwLength = sizeof(meminfo);
-       if (GlobalMemoryStatusEx(&meminfo))
-               ret = meminfo.ullTotalPhys;
+       if ((GetVersion() & 0xFF) >= 5) {
+               // Windows 2000 and later have GlobalMemoryStatusEx() which
+               // supports reporting values greater than 4 GiB. To keep the
+               // code working also on older Windows versions, use
+               // GlobalMemoryStatusEx() conditionally.
+               HMODULE kernel32 = GetModuleHandle("kernel32.dll");
+               if (kernel32 != NULL) {
+                       BOOL (WINAPI *gmse)(LPMEMORYSTATUSEX) = GetProcAddress(
+                                       kernel32, "GlobalMemoryStatusEx");
+                       if (gmse != NULL) {
+                               MEMORYSTATUSEX meminfo;
+                               meminfo.dwLength = sizeof(meminfo);
+                               if (gmse(&meminfo))
+                                       ret = meminfo.ullTotalPhys;
+                       }
+               }
+       }
+
+       if (ret == 0) {
+               // GlobalMemoryStatus() is supported by Windows 95 and later,
+               // so it is fine to link against it unconditionally. Note that
+               // GlobalMemoryStatus() has no return value.
+               MEMORYSTATUS meminfo;
+               meminfo.dwLength = sizeof(meminfo);
+               GlobalMemoryStatus(&meminfo);
+               ret = meminfo.dwTotalPhys;
+       }
 
 #elif defined(__DJGPP__)
        __dpmi_free_mem_info meminfo;