Safe LoadLibrary for DLLs that are expected to be in system32

loadlibrary_system.c

#include <windows.h>
#include <wchar.h>

#define LOAD_LIBRARY_SEARCH_SYSTEM32 (0x00000800)

HMODULE loadlibrary_system(const wchar_t* name)
{
	/* If running on Windows 8 or a system with KB2533623, LoadLibraryEx with
	   LOAD_LIBRARY_SEARCH_SYSTEM32 does the right thing */
	if (GetProcAddress(GetModuleHandleW(L"kernel32.dll"), "AddDllDirectory"))
		return LoadLibraryExW(name, NULL, LOAD_LIBRARY_SEARCH_SYSTEM32);

	wchar_t* path = malloc(MAX_PATH * sizeof(wchar_t));
	size_t pathlen = GetSystemDirectoryW(path, MAX_PATH);

	if (pathlen == 0 || pathlen + wcslen(name) + 2 > MAX_PATH)
		return NULL;

	path[pathlen] = '\\';
	wcscpy(path + pathlen + 1, name);

	HMODULE module = LoadLibraryExW(path, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);

	free(path);
	return module;
}