* cygheap.h (init_cygheap): Play more vfork shell games and move ctty_on_hold

and open_fhs_on_hold (back) here.
* dcrt0.cc (_dll_crt0): Just set impure_ptr_ptr here and let later
initialization deal with tls.
* dtable.cc (dtable::vfork_child_fixup): Move ctty considerations here.
(dtable:vfork_parent_restore): And here.
* fork.cc (vfork): Reflect change to ctty handling.
* perthread.h (vfork_save::fhctty): Eliminate.
* cygwin.din: Make more exports NOSIGFE that will never be interrupted by a
signal.
* init.cc (dll_entry): Set stackptr to NULL to catch problems earlier.

winsup/cygwin/cygwin.din

@@ -34,7 +34,7 @@ __fpclassifyd NOSIGFE
 __fpclassifyf NOSIGFE
 __getreent NOSIGFE
 __infinity NOSIGFE
-__main SIGFE
+__main NOSIGFE
 __signbitd NOSIGFE
 __signbitf NOSIGFE
 __signgam NOSIGFE
@@ -43,7 +43,7 @@ __swbuf SIGFE
 _asprintf_r SIGFE
 asprintf_r = _asprintf_r SIGFE
 _dll_crt0@0 NOSIGFE
-_exit SIGFE
+_exit NOSIGFE
 _f_atan2 NOSIGFE
 __f_atan2 = _f_atan2 NOSIGFE
 _f_atan2f NOSIGFE
@@ -290,9 +290,9 @@ cygwin_conv_to_posix_path SIGFE
 cygwin32_conv_to_posix_path = cygwin_conv_to_posix_path SIGFE
 cygwin_conv_to_win32_path SIGFE
 cygwin32_conv_to_win32_path = cygwin_conv_to_win32_path SIGFE
-cygwin_detach_dll SIGFE
-cygwin32_detach_dll = cygwin_detach_dll SIGFE
-cygwin_dll_init SIGFE
+cygwin_detach_dll NOSIGFE
+cygwin32_detach_dll = cygwin_detach_dll NOSIGFE
+cygwin_dll_init NOSIGFE
 endprotoent = cygwin_endprotoent SIGFE
 endservent = cygwin_endservent SIGFE
 endusershell SIGFE
@@ -434,7 +434,7 @@ execve SIGFE
 _execve = execve SIGFE
 execvp SIGFE
 _execvp = execvp SIGFE
-exit = cygwin_exit SIGFE
+exit = cygwin_exit NOSIGFE
 exp NOSIGFE
 _exp = exp NOSIGFE
 exp2 NOSIGFE