* miscfuncs.cc (DEFAULT_STACKSIZE): Remove.

(CygwinCreateThread): Simplify code by assuming that now stack-related
	input values are undefined.  Set stack protection to PAGE_READWRITE,
	as is default on Windows.  Add lengthy comment to explain POSIX
	guardpage.
	* thread.cc (pthread_attr::pthread_attr): Initialize stacksize as
	PTHREAD_DEFAULT_STACKSIZE.  Initialize guardsize as
	PTHREAD_DEFAULT_GUARDSIZE.
	* thread.h (PTHREAD_DEFAULT_STACKSIZE): Define.  Add comment to explain.
	(PTHREAD_DEFAULT_GUARDSIZE): Define.

winsup/cygwin/ChangeLog

@@ -1,3 +1,16 @@
+2012-02-11  Corinna Vinschen  <corinna@vinschen.de>
+
+	* miscfuncs.cc (DEFAULT_STACKSIZE): Remove.
+	(CygwinCreateThread): Simplify code by assuming that now stack-related
+	input values are undefined.  Set stack protection to PAGE_READWRITE,
+	as is default on Windows.  Add lengthy comment to explain POSIX
+	guardpage.
+	* thread.cc (pthread_attr::pthread_attr): Initialize stacksize as
+	PTHREAD_DEFAULT_STACKSIZE.  Initialize guardsize as
+	PTHREAD_DEFAULT_GUARDSIZE.
+	* thread.h (PTHREAD_DEFAULT_STACKSIZE): Define.  Add comment to explain.
+	(PTHREAD_DEFAULT_GUARDSIZE): Define.
+
 2012-02-10  Corinna Vinschen  <corinna@vinschen.de>
 
 	* miscfuncs.cc (DEFAULT_STACKSIZE): Set to 1 Megs.  Drop comment about

winsup/cygwin/miscfuncs.cc

@@ -549,8 +549,6 @@ thread_wrapper (VOID *arg)
   ExitThread (0);
 }
 
-#define DEFAULT_STACKSIZE (1024 * 1024)
-
 HANDLE WINAPI
 CygwinCreateThread (LPTHREAD_START_ROUTINE thread_func, PVOID thread_arg,
 		    PVOID stackaddr, ULONG stacksize, ULONG guardsize,
@@ -572,29 +570,18 @@ CygwinCreateThread (LPTHREAD_START_ROUTINE thread_func, PVOID thread_arg,
   wrapper_arg->func = thread_func;
   wrapper_arg->arg = thread_arg;
 
-  /* Set stacksize. */
-  real_stacksize = stacksize ?: DEFAULT_STACKSIZE;
-  if (real_stacksize < PTHREAD_STACK_MIN)
-    real_stacksize = PTHREAD_STACK_MIN;
   if (stackaddr)
     {
       /* If the application provided the stack, just use it. */
       wrapper_arg->stackaddr = (char *) stackaddr;
-      wrapper_arg->stackbase = (char *) stackaddr + real_stacksize;
+      wrapper_arg->stackbase = (char *) stackaddr + stacksize;
     }
   else
     {
       /* If not, we have to create the stack here. */
-      real_stacksize = roundup2 (real_stacksize, wincap.page_size ());
+      real_stacksize = roundup2 (stacksize, wincap.page_size ());
-      /* If no guardsize has been specified by the application, use the
+      real_guardsize = roundup2 (guardsize, wincap.page_size ());
-	 system pagesize as default. */
+      /* Add the guardsize to the stacksize */
-      real_guardsize = (guardsize != (ULONG) -1)
-		       ? guardsize : wincap.page_size ();
-      if (real_guardsize)
-	real_guardsize = roundup2 (real_guardsize, wincap.page_size ());
-      /* Add the guardsize to the stacksize, but only if the stacksize and
-	 the guardsize have been explicitely specified. */
-      if (stacksize || guardsize != (ULONG) -1)
       real_stacksize += real_guardsize;
       /* Now roundup the result to the next allocation boundary. */
       real_stacksize = roundup2 (real_stacksize,
@@ -606,7 +593,7 @@ CygwinCreateThread (LPTHREAD_START_ROUTINE thread_func, PVOID thread_arg,
 	 the Cygwin DLL comes to mind. */
       real_stackaddr = VirtualAlloc (NULL, real_stacksize,
 				     MEM_RESERVE | MEM_TOP_DOWN,
-				     PAGE_EXECUTE_READWRITE);
+				     PAGE_READWRITE);
       if (!real_stackaddr)
 	return NULL;
       /* Set up committed region.  In contrast to the OS we commit 64K and
@@ -615,13 +602,19 @@ CygwinCreateThread (LPTHREAD_START_ROUTINE thread_func, PVOID thread_arg,
 				  + real_stacksize
 				  - wincap.allocation_granularity ();
       if (!VirtualAlloc (commitaddr, wincap.page_size (), MEM_COMMIT,
-			 PAGE_EXECUTE_READWRITE | PAGE_GUARD))
+			 PAGE_READWRITE | PAGE_GUARD))
 	goto err;
       commitaddr += wincap.page_size ();
       if (!VirtualAlloc (commitaddr, wincap.allocation_granularity ()
 				     - wincap.page_size (), MEM_COMMIT,
-			 PAGE_EXECUTE_READWRITE))
+			 PAGE_READWRITE))
 	goto err;
+      /* If the guardsize is != 0 (which is the default), set up a POSIX
+      	 guardpage at the end of the stack. This isn't the same as the
+	 Windows guardpage, which is used to convert reserved stack to
+	 commited stack if necessary.  Rather, the POSIX guardpage consists
+	 of one or more memory pages with NOACCESS protection.  It's supposed
+	 to safeguard memory areas beyond the stack against stack overflow. */
       if (real_guardsize)
 	VirtualAlloc (real_stackaddr, real_guardsize, MEM_COMMIT,
 		      PAGE_NOACCESS);

winsup/cygwin/thread.cc

@@ -1127,8 +1127,8 @@ pthread::resume ()
 
 pthread_attr::pthread_attr ():verifyable_object (PTHREAD_ATTR_MAGIC),
 joinable (PTHREAD_CREATE_JOINABLE), contentionscope (PTHREAD_SCOPE_PROCESS),
-inheritsched (PTHREAD_INHERIT_SCHED), stackaddr (NULL), stacksize (0),
+inheritsched (PTHREAD_INHERIT_SCHED), stackaddr (NULL),
-guardsize ((size_t) -1)
+stacksize (PTHREAD_DEFAULT_STACKSIZE), guardsize (PTHREAD_DEFAULT_GUARDSIZE)
 {
   schedparam.sched_priority = 0;
 }

winsup/cygwin/thread.h

@@ -16,6 +16,12 @@ details. */
 #define WRITE_LOCK 1
 #define READ_LOCK  2
 
+/* Default is a 1 Megs stack with a 4K guardpage.  Since the pthread stacksize
+   does not include the guardpage size, but we don't want to waste another 64K,
+   subtract the default guardpage size from the stacksize. */
+#define PTHREAD_DEFAULT_STACKSIZE (1024 * 1024 - wincap.page_size ())
+#define PTHREAD_DEFAULT_GUARDSIZE (wincap.page_size ())
+
 #include <pthread.h>
 #include <limits.h>
 #include "security.h"