test-drop-caches: simplify delay loading of NtSetSystemInformation

Take advantage of the recent addition of support for lazy loading functions[1]
on Windows to simplify the loading of NtSetSystemInformation.

[1] db2f7c4 (Win32: simplify loading of DLL functions, 2017-09-25)

Signed-off-by: Ben Peart <[email protected]>
Reviewed-by: Johannes Schindelin <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Ben Peart

t/helper/test-drop-caches.c

@@ -2,6 +2,7 @@
 #include "git-compat-util.h"
 
 #if defined(GIT_WINDOWS_NATIVE)
+#include "lazyload.h"
 
 static int cmd_sync(void)
 {
@@ -82,8 +83,7 @@ static int cmd_dropcaches(void)
 {
 	HANDLE hProcess = GetCurrentProcess();
 	HANDLE hToken;
-	HMODULE ntdll;
-	DWORD(WINAPI *NtSetSystemInformation)(INT, PVOID, ULONG);
+	DECLARE_PROC_ADDR(ntdll.dll, DWORD, NtSetSystemInformation, INT, PVOID, ULONG);
 	SYSTEM_MEMORY_LIST_COMMAND command;
 	int status;
 
@@ -95,14 +95,8 @@ static int cmd_dropcaches(void)
 
 	CloseHandle(hToken);
 
-	ntdll = LoadLibrary("ntdll.dll");
-	if (!ntdll)
-		return error("Can't load ntdll.dll, wrong Windows version?");
-
-	NtSetSystemInformation =
-		(DWORD(WINAPI *)(INT, PVOID, ULONG))GetProcAddress(ntdll, "NtSetSystemInformation");
-	if (!NtSetSystemInformation)
-		return error("Can't get function addresses, wrong Windows version?");
+	if (!INIT_PROC_ADDR(NtSetSystemInformation))
+		return error("Could not find NtSetSystemInformation() function");
 
 	command = MemoryPurgeStandbyList;
 	status = NtSetSystemInformation(
@@ -115,8 +109,6 @@ static int cmd_dropcaches(void)
 	else if (status != STATUS_SUCCESS)
 		error("Unable to execute the memory list command %d", status);
 
-	FreeLibrary(ntdll);
-
 	return status;
 }