[libxml2] Fix potentially-uninitialized critical section in Win32 DLL builds

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 453bdfb95edd725fac1ca1c42634e8c9739b03fa
Author: Kevin Puetz <PuetzKevinA JohnDeere com>
Date:   Mon Jan 13 18:28:34 2020 -0600

    Fix potentially-uninitialized critical section in Win32 DLL builds
    
    If non-parser parts of libxml (e.g. xmlwriter) are used before a parser,
    xmlOnceInit may have run (e.g. via the many paths to xmlGetGlobalState),
    but not xmlInitThreads (which is called only by xmlInitParser)
    
    Once globalkey != TLS_OUT_OF_INDEXES (which can happen in many ways),
    DLLMAIN(DLL_THREAD_DETACH) may attempt to lock cleanup_helpers_cs
    before it is valid. This may happen even if the thread whose exit
    is triggering DllMain is from code which is not linked to libxml.
    
    globalkey and cleanup_helpers_cs should be initialized together,
    with cleanup_helpers_cs initialized first and deleted last.

 threads.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/threads.c b/threads.c
index 72df9ba9..503d2bfb 100644
--- a/threads.c
+++ b/threads.c
@@ -885,8 +885,6 @@ xmlInitThreads(void)
         }
     }
 #endif /* XML_PTHREAD_WEAK */
-#elif defined(HAVE_WIN32_THREADS) && !defined(HAVE_COMPILER_TLS) && (!defined(LIBXML_STATIC) || 
defined(LIBXML_STATIC_FOR_DLL))
-    InitializeCriticalSection(&cleanup_helpers_cs);
 #endif
 }
 
@@ -958,6 +956,9 @@ xmlOnceInit(void)
     if (!run_once.done) {
         if (InterlockedIncrement(&run_once.control) == 1) {
 #if !defined(HAVE_COMPILER_TLS)
+#if !defined(LIBXML_STATIC) || defined(LIBXML_STATIC_FOR_DLL)
+            InitializeCriticalSection(&cleanup_helpers_cs);
+#endif
             globalkey = TlsAlloc();
 #endif
             mainthread = GetCurrentThreadId();