ntdll: Implement _errno().

dlls/ntdll/loader.c

@@ -4216,6 +4216,7 @@ void WINAPI LdrInitializeThunk( CONTEXT *context, ULONG_PTR unknown2, ULONG_PTR
                              sizeof(peb->TlsExpansionBitmapBits) * 8 );
         /* TLS index 0 is always reserved, and wow64 reserves extra TLS entries */
         RtlSetBits( peb->TlsBitmap, 0, NtCurrentTeb()->WowTebOffset ? WOW64_TLS_MAX_NUMBER : 1 );
+        RtlSetBits( peb->TlsBitmap, NTDLL_TLS_ERRNO, 1 );
 
         init_user_process_params();
         load_global_options();

dlls/ntdll/ntdll.spec

@@ -1514,6 +1514,7 @@
 @ cdecl -norelay -arch=i386 -ret64 _aullrem(int64 int64)
 @ cdecl -norelay -arch=i386 -ret64 _aullshr(int64 long)
 @ cdecl -arch=i386 -norelay _chkstk()
+@ cdecl _errno()
 @ stub _fltused
 @ cdecl -arch=i386 -ret64 _ftol()
 @ cdecl -arch=i386 -ret64 _ftol2() _ftol

dlls/ntdll/ntdll_misc.h

@@ -39,6 +39,8 @@
 
 #define MAX_NT_PATH_LENGTH 277
 
+#define NTDLL_TLS_ERRNO 16  /* TLS slot for _errno() */
+
 #if defined(__i386__) || defined(__x86_64__) || defined(__arm__) || defined(__aarch64__)
 static const UINT_PTR page_size = 0x1000;
 #else

dlls/ntdll/tests/thread.c

@@ -24,12 +24,14 @@
 static NTSTATUS (WINAPI *pNtCreateThreadEx)( HANDLE *, ACCESS_MASK, OBJECT_ATTRIBUTES *,
                                              HANDLE, PRTL_THREAD_START_ROUTINE, void *,
                                              ULONG, ULONG_PTR, SIZE_T, SIZE_T, PS_ATTRIBUTE_LIST * );
+static int * (CDECL *p_errno)(void);
 
 static void init_function_pointers(void)
 {
     HMODULE hntdll = GetModuleHandleA( "ntdll.dll" );
 #define GET_FUNC(name) p##name = (void *)GetProcAddress( hntdll, #name );
     GET_FUNC( NtCreateThreadEx );
+    GET_FUNC( _errno );
 #undef GET_FUNC
 }
 
@@ -177,10 +179,29 @@ static void test_unique_teb(void)
     ok( args1.teb != args2.teb, "Multiple threads have TEB %p.\n", args1.teb );
 }
 
+static void test_errno(void)
+{
+    int val;
+
+    if (!p_errno)
+    {
+        win_skip( "_errno not available\n" );
+        return;
+    }
+    ok( NtCurrentTeb()->Peb->TlsBitmap->Buffer[0] & (1 << 16), "TLS entry 16 not allocated\n" );
+    *p_errno() = 0xdead;
+    val = PtrToLong( TlsGetValue( 16 ));
+    ok( val == 0xdead, "wrong value %x\n", val );
+    *p_errno() = 0xbeef;
+    val = PtrToLong( TlsGetValue( 16 ));
+    ok( val == 0xbeef, "wrong value %x\n", val );
+}
+
 START_TEST(thread)
 {
     init_function_pointers();
 
     test_dbg_hidden_thread_creation();
     test_unique_teb();
+    test_errno();
 }

dlls/ntdll/thread.c

@@ -464,6 +464,15 @@ TEB_ACTIVE_FRAME * WINAPI RtlGetFrame(void)
 
 
 /***********************************************************************
+ *           _errno  (NTDLL.@)
+ */
+int * CDECL _errno(void)
+{
+    return (int *)&NtCurrentTeb()->TlsSlots[NTDLL_TLS_ERRNO];
+}
+
+
+/***********************************************************************
  * Fibers
  ***********************************************************************/