Rename parent stack members in child_info struct to align with OS names

        * child_info.h (CURR_CHILD_INFO_MAGIC): Align to below change.
        (class child_info_fork): Rename stacktop to stacklimit.  Rename
        stackbottom to stackbase.  Accommodate name change throughout Cygwin.
        Rephrase comments to be clearer.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

4 files changed, 36 insertions, 28 deletions

diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index c74d1ba60..cffd7c2ca 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,5 +1,12 @@
 2015-12-02  Corinna Vinschen  <corinna@vinschen.de>
 
+	* child_info.h (CURR_CHILD_INFO_MAGIC): Align to below change.
+	(class child_info_fork): Rename stacktop to stacklimit.  Rename
+	stackbottom to stackbase.  Accommodate name change throughout Cygwin.
+	Rephrase comments to be clearer.
+
+2015-12-02  Corinna Vinschen  <corinna@vinschen.de>
+
 	* cygtls.h (_tlsbase): Remove.  Replace throughout with
 	NtCurrentTeb()->Tib.StackBase.
 	(_tlstop): Remove. Replace throughout with
diff --git a/winsup/cygwin/child_info.h b/winsup/cygwin/child_info.h
index 7d8d0b818..1ec612788 100644
--- a/winsup/cygwin/child_info.h
+++ b/winsup/cygwin/child_info.h
@@ -39,7 +39,7 @@ enum child_status
 #define EXEC_MAGIC_SIZE sizeof(child_info)
 
 /* Change this value if you get a message indicating that it is out-of-sync. */
-#define CURR_CHILD_INFO_MAGIC 0x4a91a908U
+#define CURR_CHILD_INFO_MAGIC 0xc96f5e9U
 
 #define NPROCS	256
 
@@ -103,9 +103,10 @@ class child_info_fork: public child_info
 public:
   HANDLE forker_finished;// for synchronization with child
   jmp_buf jmp;		// where child will jump to
-  void *stackaddr;	// address of parent stack
-  void *stacktop;	// location of top of parent stack
-  void *stackbottom;	// location of bottom of parent stack
+  void *stackaddr;	// DeallocationStack or user-provided allocation address
+			// of parent thread
+  void *stacklimit;	// StackLimit of parent thread
+  void *stackbase;	// StackBase of parent thread
   size_t guardsize;     // size of POSIX guard region or (size_t) -1 if
 			// user stack
   char filler[4];
diff --git a/winsup/cygwin/dcrt0.cc b/winsup/cygwin/dcrt0.cc
index 7ec0ba3bf..de95121c7 100644
--- a/winsup/cygwin/dcrt0.cc
+++ b/winsup/cygwin/dcrt0.cc
@@ -412,15 +412,15 @@ child_info_fork::alloc_stack ()
   /* Make sure not to try a hard allocation if we have been forked off from
      the main thread of a Cygwin process which has been started from a 64 bit
      parent.  In that case the StackBase of the forked child is not the same
-     as the StackBase of the parent (== stackbottom), but only because the
+     as the StackBase of the parent (== this.stackbase), but only because the
      stack of the parent has been slightly rearranged.  See comment in
      wow64_revert_to_original_stack for details. We check here if the
      parent stack fits into the child stack. */
   PTEB teb = NtCurrentTeb ();
-  if (teb->Tib.StackBase != stackbottom
+  if (teb->Tib.StackBase != stackbase
       && (!wincap.is_wow64 ()
-	  || stacktop < teb->DeallocationStack
-	  || stackbottom > teb->Tib.StackBase))
+	  || stacklimit < teb->DeallocationStack
+	  || stackbase > teb->Tib.StackBase))
     {
       void *stack_ptr;
       size_t stacksize;
@@ -430,21 +430,21 @@ child_info_fork::alloc_stack ()
       if (guardsize == (size_t) -1)
 	return;
       /* Reserve entire stack. */
-      stacksize = (PBYTE) stackbottom - (PBYTE) stackaddr;
+      stacksize = (PBYTE) stackbase - (PBYTE) stackaddr;
       if (!VirtualAlloc (stackaddr, stacksize, MEM_RESERVE, PAGE_NOACCESS))
 	{
 	  api_fatal ("fork: can't reserve memory for parent stack "
 		     "%p - %p, (child has %p - %p), %E",
-		     stackaddr, stackbottom, teb->DeallocationStack,
+		     stackaddr, stackbase, teb->DeallocationStack,
 		     teb->Tib.StackBase);
 	}
       /* Commit the area commited in parent. */
-      stacksize = (PBYTE) stackbottom - (PBYTE) stacktop;
-      stack_ptr = VirtualAlloc (stacktop, stacksize, MEM_COMMIT,
+      stacksize = (PBYTE) stackbase - (PBYTE) stacklimit;
+      stack_ptr = VirtualAlloc (stacklimit, stacksize, MEM_COMMIT,
 				PAGE_READWRITE);
       if (!stack_ptr)
 	api_fatal ("can't commit memory for stack %p(%ly), %E",
-		   stacktop, stacksize);
+		   stacklimit, stacksize);
       /* Set up guardpages. */
       ULONG real_guardsize = guardsize
 			     ? roundup2 (guardsize, wincap.page_size ())
@@ -472,26 +472,26 @@ child_info_fork::alloc_stack ()
       /* Fork has been called from main thread.  Simply commit the region
 	 of the stack commited in the parent but not yet commited in the
 	 child and create new guardpages. */
-      if (NtCurrentTeb()->Tib.StackLimit > stacktop)
+      if (NtCurrentTeb()->Tib.StackLimit > stacklimit)
 	{
 	  SIZE_T commitsize = (PBYTE) NtCurrentTeb()->Tib.StackLimit
-			      - (PBYTE) stacktop;
-	  if (!VirtualAlloc (stacktop, commitsize, MEM_COMMIT, PAGE_READWRITE))
+			      - (PBYTE) stacklimit;
+	  if (!VirtualAlloc (stacklimit, commitsize, MEM_COMMIT, PAGE_READWRITE))
 	    api_fatal ("can't commit child memory for stack %p(%ly), %E",
-		       stacktop, commitsize);
-	  PVOID guardpage = (PBYTE) stacktop - wincap.def_guard_page_size ();
+		       stacklimit, commitsize);
+	  PVOID guardpage = (PBYTE) stacklimit - wincap.def_guard_page_size ();
 	  if (!VirtualAlloc (guardpage, wincap.def_guard_page_size (),
 			     MEM_COMMIT, PAGE_READWRITE | PAGE_GUARD))
 	    api_fatal ("fork: couldn't allocate new stack guard page %p, %E",
 		       guardpage);
-	  NtCurrentTeb()->Tib.StackLimit = stacktop;
+	  NtCurrentTeb()->Tib.StackLimit = stacklimit;
 	}
       stackaddr = 0;
       /* This only affects forked children of a process started from a native
 	 64 bit process, but it doesn't hurt to do it unconditionally.  Fix
 	 StackBase in the child to be the same as in the parent, so that the
 	 computation of _my_tls is correct. */
-      teb->Tib.StackBase = (PVOID) stackbottom;
+      teb->Tib.StackBase = (PVOID) stackbase;
     }
 }
 
@@ -920,8 +920,8 @@ dll_crt0_1 (void *)
 	 this step. */
       if (fork_info->stackaddr)
 	{
-	  NtCurrentTeb()->Tib.StackBase = (PVOID) fork_info->stackbottom;
-	  NtCurrentTeb()->Tib.StackLimit = (PVOID) fork_info->stacktop;
+	  NtCurrentTeb()->Tib.StackBase = (PVOID) fork_info->stackbase;
+	  NtCurrentTeb()->Tib.StackLimit = (PVOID) fork_info->stacklimit;
 	}
 
       /* Not resetting _my_tls.incyg here because presumably fork will overwrite
diff --git a/winsup/cygwin/fork.cc b/winsup/cygwin/fork.cc
index 78ae932d3..d4a973eb2 100644
--- a/winsup/cygwin/fork.cc
+++ b/winsup/cygwin/fork.cc
@@ -307,7 +307,7 @@ frok::parent (volatile char * volatile stack_here)
 
   ch.forker_finished = forker_finished;
 
-  ch.stackbottom = NtCurrentTeb()->Tib.StackBase;
+  ch.stackbase = NtCurrentTeb()->Tib.StackBase;
   ch.stackaddr = NtCurrentTeb ()->DeallocationStack;
   if (!ch.stackaddr)
     {
@@ -315,25 +315,25 @@ frok::parent (volatile char * volatile stack_here)
 	 stack.  If so, the entire stack is committed anyway and StackLimit
 	 points to the allocation address of the stack.  Mark in guardsize that
 	 we must not set up guard pages. */
-      ch.stackaddr = ch.stacktop = NtCurrentTeb()->Tib.StackLimit;
+      ch.stackaddr = ch.stacklimit = NtCurrentTeb()->Tib.StackLimit;
       ch.guardsize = (size_t) -1;
     }
   else
     {
       /* Otherwise we're running on a system-allocated stack.  Since stack_here
 	 is the address of the stack pointer we start the child with anyway, we
-	 can set ch.stacktop to this value rounded down to page size.  The
+	 can set ch.stacklimit to this value rounded down to page size.  The
 	 child will not need the rest of the stack anyway.  Guardsize depends
 	 on whether we're running on a pthread or not.  If pthread, we fetch
 	 the guardpage size from the pthread attribs, otherwise we use the
 	 system default. */
-      ch.stacktop = (void *) ((uintptr_t) stack_here & ~wincap.page_size ());
+      ch.stacklimit = (void *) ((uintptr_t) stack_here & ~wincap.page_size ());
       ch.guardsize = (&_my_tls != _main_tls && _my_tls.tid)
 		     ? _my_tls.tid->attr.guardsize
 		     : wincap.def_guard_page_size ();
     }
   debug_printf ("stack - bottom %p, top %p, addr %p, guardsize %ly",
-		ch.stackbottom, ch.stacktop, ch.stackaddr, ch.guardsize);
+		ch.stackbase, ch.stacklimit, ch.stackaddr, ch.guardsize);
 
   PROCESS_INFORMATION pi;
   STARTUPINFOW si;
@@ -475,7 +475,7 @@ frok::parent (volatile char * volatile stack_here)
       impure_end = _impure_ptr + 1;
     }
   rc = child_copy (hchild, true,
-		   "stack", stack_here, ch.stackbottom,
+		   "stack", stack_here, ch.stackbase,
 		   impure, impure_beg, impure_end,
 		   NULL);