msvc-inval multithread-safe [1/2]

[Bruno Haible]

There is one copy of the "invalid parameter handler" in the MSVC runtime
library; there is not one copy per thread. Therefore, setting this handler
or deinstalling it in a gnulib function is not multithread-safe. For MT-safety
the module needs two changes:
  1) Install the handler once, globally.
  2) Allocate the jmp_buf per thread.

Here comes part 1.


2011-09-25  Bruno Haible  <address@hidden>

        msvc-inval: Install handler globally.
        * lib/msvc-inval.h (STATUS_GNULIB_INVALID_PARAMETER): Define also for
        !_MSC_VER.
        (gl_msvc_invalid_parameter_handler): Remove declaration.
        (gl_msvc_inval_restart_valid, gl_msvc_inval_ensure_handler): New
        declarations.
        (TRY_MSVC_INVAL, CATCH_MSVC_INVAL, DONE_MSVC_INVAL) [!_MSC_VER]:
        Install the handler globally, don't uninstall it.
        * lib/msvc-inval.c (gl_msvc_inval_restart_valid): New variable.
        (gl_msvc_invalid_parameter_handler): Make static. If the restart is not
        currently valid, call RaiseException instead.
        (gl_msvc_inval_initialized, gl_msvc_inval_ensure_handler): Define also
        for !_MSC_VER.

--- lib/msvc-inval.h.orig       Sun Sep 25 20:58:50 2011
+++ lib/msvc-inval.h    Sun Sep 25 18:48:03 2011
@@ -47,14 +47,7 @@
 /* Get _invalid_parameter_handler type and _set_invalid_parameter_handler
    declaration.  */
 # include <stdlib.h>
-
-# if defined _MSC_VER
-/* A compiler that supports __try/__except, as described in the page
-   "try-except statement" on microsoft.com
-   <http://msdn.microsoft.com/en-us/library/s58ftw19.aspx>.
-   With __try/__except, we can use the multithread-safe exception handling.  */
-
-#  include <excpt.h>
+# include <excpt.h>
 
 /* Gnulib can define its own status codes, as described in the page
    "Raising Software Exceptions" on microsoft.com
@@ -64,7 +57,13 @@
      - 0x474E550, a API identifier ("GNU"),
      - 0, 1, 2, ..., used to distinguish different status codes from the
        same API.  */
-#  define STATUS_GNULIB_INVALID_PARAMETER (0xE0000000 + 0x474E550 + 0)
+# define STATUS_GNULIB_INVALID_PARAMETER (0xE0000000 + 0x474E550 + 0)
+
+# if defined _MSC_VER
+/* A compiler that supports __try/__except, as described in the page
+   "try-except statement" on microsoft.com
+   <http://msdn.microsoft.com/en-us/library/s58ftw19.aspx>.
+   With __try/__except, we can use the multithread-safe exception handling.  */
 
 #  ifdef __cplusplus
 extern "C" {
@@ -95,8 +94,7 @@
 
 # else
 /* Any compiler.
-   We can only use setjmp/longjmp.
-   Unfortunately, this is *not* multithread-safe.  */
+   We can only use setjmp/longjmp.  */
 
 #  include <setjmp.h>
 
@@ -109,14 +107,15 @@
    TRY_MSVC_INVAL and CATCH_MSVC_INVAL.  */
 extern jmp_buf gl_msvc_inval_restart;
 
-/* The invalid parameter handler that unwinds the stack up to the
-   gl_msvc_inval_restart.  It is enabled only between TRY_MSVC_INVAL
-   and CATCH_MSVC_INVAL.  */
-extern void cdecl gl_msvc_invalid_parameter_handler (const wchar_t *expression,
-                                                     const wchar_t *function,
-                                                     const wchar_t *file,
-                                                     unsigned int line,
-                                                     uintptr_t dummy);
+/* Tells whether the contents of gl_msvc_inval_restart is valid.  */
+extern int gl_msvc_inval_restart_valid;
+
+/* Ensure that the invalid parameter handler in installed that passes
+   control to the gl_msvc_inval_restart if it is valid, or raises a
+   software exception with code STATUS_GNULIB_INVALID_PARAMETER otherwise.
+   Because we assume no other part of the program installs a different
+   invalid parameter handler, this solution is multithread-safe.  */
+extern void gl_msvc_inval_ensure_handler (void);
 
 #  ifdef __cplusplus
 }
@@ -125,23 +124,22 @@
 #  define TRY_MSVC_INVAL \
      do                                                                        
\
        {                                                                       
\
-         _invalid_parameter_handler orig_handler;                              
\
+         gl_msvc_inval_ensure_handler ();                                      
\
          /* First, initialize gl_msvc_inval_restart.  */                       
\
          if (setjmp (gl_msvc_inval_restart) == 0)                              
\
            {                                                                   
\
-             /* Then, enable gl_msvc_invalid_parameter_handler.  */            
\
-             orig_handler =                                                    
\
-               _set_invalid_parameter_handler 
(gl_msvc_invalid_parameter_handler);
+             /* Then, mark it as valid.  */                                    
\
+             gl_msvc_inval_restart_valid = 1;
 #  define CATCH_MSVC_INVAL \
              /* Execution completed.                                           
\
-                Disable gl_msvc_invalid_parameter_handler.  */                 
\
-             _set_invalid_parameter_handler (orig_handler);                    
\
+                Mark gl_msvc_inval_restart as invalid.  */                     
\
+             gl_msvc_inval_restart_valid = 0;                                  
\
            }                                                                   
\
          else                                                                  
\
            {                                                                   
\
              /* Execution triggered an invalid parameter notification.         
\
-                Disable gl_msvc_invalid_parameter_handler.  */                 
\
-             _set_invalid_parameter_handler (orig_handler);
+                Mark gl_msvc_inval_restart as invalid.  */                     
\
+             gl_msvc_inval_restart_valid = 0;
 #  define DONE_MSVC_INVAL \
            }                                                                   
\
        }                                                                       
\
--- lib/msvc-inval.c.orig       Sun Sep 25 20:58:50 2011
+++ lib/msvc-inval.c    Sun Sep 25 18:48:00 2011
@@ -22,11 +22,11 @@
 
 #if HAVE_MSVC_INVALID_PARAMETER_HANDLER
 
-# ifdef STATUS_GNULIB_INVALID_PARAMETER
-
 /* Get declarations of the Win32 API functions.  */
-#  define WIN32_LEAN_AND_MEAN
-#  include <windows.h>
+# define WIN32_LEAN_AND_MEAN
+# include <windows.h>
+
+# if defined _MSC_VER
 
 static void cdecl
 gl_msvc_invalid_parameter_handler (const wchar_t *expression,
@@ -38,32 +38,38 @@
   RaiseException (STATUS_GNULIB_INVALID_PARAMETER, 0, 0, NULL);
 }
 
-static int gl_msvc_inval_initialized /* = 0 */;
-
-void
-gl_msvc_inval_ensure_handler (void)
-{
-  if (gl_msvc_inval_initialized == 0)
-    {
-      _set_invalid_parameter_handler (gl_msvc_invalid_parameter_handler);
-      gl_msvc_inval_initialized = 1;
-    }
-}
-
 # else
 
 jmp_buf gl_msvc_inval_restart;
+int gl_msvc_inval_restart_valid;
 
-void cdecl
+static void cdecl
 gl_msvc_invalid_parameter_handler (const wchar_t *expression,
                                    const wchar_t *function,
                                    const wchar_t *file,
                                    unsigned int line,
                                    uintptr_t dummy)
 {
-  longjmp (gl_msvc_inval_restart, 1);
+  if (gl_msvc_inval_restart_valid)
+    longjmp (gl_msvc_inval_restart, 1);
+  else
+    /* An invalid parameter notification from outside the gnulib code.
+       Give the caller a chance to intervene.  */
+    RaiseException (STATUS_GNULIB_INVALID_PARAMETER, 0, 0, NULL);
 }
 
 # endif
 
+static int gl_msvc_inval_initialized /* = 0 */;
+
+void
+gl_msvc_inval_ensure_handler (void)
+{
+  if (gl_msvc_inval_initialized == 0)
+    {
+      _set_invalid_parameter_handler (gl_msvc_invalid_parameter_handler);
+      gl_msvc_inval_initialized = 1;
+    }
+}
+
 #endif

-- 
In memoriam Safia Ahmed-jan <http://en.wikipedia.org/wiki/Safia_Ahmed-jan>