ada: New pragma to default all interrupts to system.

New pragma Interrupts_System_By_Default defaults all interrupts/signals
to system (which will inhibit the installation of default signal handlers).
Note this changes the ALI format: it optionally adds an identifier to
the 'P' line (similar to pragma Unreserve_All_Interrupts). As per comment
in lib-writ spec regarding new modifiers, adding modifiers to the P line
is always safe. Also note this does not introduce a bootstrap problem
because the compiler and binder do not set the underlying _gl global nor
do they use this pragma.

gcc/ada/

	* ali.ads (Interrupts_Default_To_System): New boolean.
	(Interrupts_Default_To_System_Specified): New boolean.
	* ali.adb (Interrupts_Default_To_System_Specified): Initialize.
	(Interrupts_Default_To_System): Initialize.
	(Scan_ALI): Processing for "ID".
	* bindgen.adb: Coallesce comments on interrupt settings to ...
	(Gen_Adainit): Import Interrupts_Default_To_System flag and set if
	pragma specified.
	(Gen_Output_File_Ada): Generate Local_Interrupt_States according
	to pragma.
	* init.c: ... here.
	[vxworks] (__gnat_install_handler): Test for interrupt_state.
	(__gl_interrupts_default_to_system): New global flag.
	(__gnat_get_interrupt_State): return interrupt state according to
	new global flag.
	* lib-writ.ads: Document "ID".
	* lib-writ.adb: Write out "ID".
	* opt.ads (Interrupts_System_By_Default): New boolean, defaulted
	to False.
	* par-prag.adb (Pragma_Interrupts_System_By_Default): New.
	* sem_prag.adb (Pragma_Interrupts_System_By_Default): Handle it.
	(Pragma_Interrupts_System_By_Default): Default it.
	* snames.ads-tmpl (Name_Interrupts_System_By_Default): New name.
	(Pragma_Interrupts_System_By_Default): New
	* libgnarl/s-intman__posix.adb (Initialize): Ensure the
	Keep_Unmasked signal is sigset-able.
	* doc/gnat_rm/implementation_defined_pragmas.rst: Document pragma
	Interrupts_System_By_Default.
	* doc/gnat_ugn/the_gnat_compilation_model.rst (Configuration
	pragmas): Add Interrupts_System_By_Default. (Partition-Wide
	Settings): Mention pragma Interrupts_System_By_Default.
	* gnat_rm.texi: Regenerate.
	* gnat_ugn.texi: Regenerate.

1 files changed, 22 insertions, 12 deletions

diff --git a/gcc/ada/init.c b/gcc/ada/init.c
index 7cf7747..acb8c7c 100644
--- a/gcc/ada/init.c
+++ b/gcc/ada/init.c
@@ -122,6 +122,7 @@ int   __gl_leap_seconds_support          = 0;
 int   __gl_canonical_streams             = 0;
 char *__gl_bind_env_addr                 = NULL;
 int   __gl_xdr_stream                    = 0;
+int   __gl_interrupts_default_to_system  = 0;
 
 /* This value is not used anymore, but kept for bootstrapping purpose.  */
 int   __gl_zero_cost_exceptions          = 0;
@@ -148,20 +149,25 @@ int __gnat_inside_elab_final_code = 0;
 char __gnat_get_interrupt_state (int);
 
 /* This routine is called from the runtime as needed to determine the state
-   of an interrupt, as set by an Interrupt_State pragma appearing anywhere
-   in the current partition.  The input argument is the interrupt number,
-   and the result is one of the following:
+   of an interrupt, as set by an Interrupt_State pragma or an
+   Interrupts_System_By_Default pragma appearing anywhere in the current
+   partition.  The input argument is the interrupt number, and the result
+   is one of the following:
 
-       'n'   this interrupt not set by any Interrupt_State pragma
-       'u'   Interrupt_State pragma set state to User
-       'r'   Interrupt_State pragma set state to Runtime
-       's'   Interrupt_State pragma set state to System  */
+       'u'   if Interrupt_State pragma set to User;
+       'r'   if Interrupt_State pragma set to Runtime;
+       's'   if Interrupt_State pragma set to System or
+             Interrupts_System_By_Default in effect; otherwise
+       'n'   (there is no Interrupt_State pragma and no request for a default).
+
+   See pragma Interrupt_State documentation for a description
+   of the effect and meaning of states User, Runtime, and System.  */
 
 char
 __gnat_get_interrupt_state (int intrup)
 {
   if (intrup >= __gl_num_interrupt_states)
-    return 'n';
+    return (__gl_interrupts_default_to_system ? 's' : 'n');
   else
     return __gl_interrupt_states [intrup];
 }
@@ -2094,10 +2100,14 @@ __gnat_install_handler (void)
 
   /* For VxWorks, install all signal handlers, since pragma Interrupt_State
      applies to vectored hardware interrupts, not signals.  */
-  sigaction (SIGFPE,  &act, NULL);
-  sigaction (SIGILL,  &act, NULL);
-  sigaction (SIGSEGV, &act, NULL);
-  sigaction (SIGBUS,  &act, NULL);
+  if (__gnat_get_interrupt_state (SIGFPE) != 's')
+     sigaction (SIGFPE,  &act, NULL);
+  if (__gnat_get_interrupt_state (SIGILL) != 's')
+     sigaction (SIGILL,  &act, NULL);
+  if (__gnat_get_interrupt_state (SIGSEGV) != 's')
+     sigaction (SIGSEGV, &act, NULL);
+  if (__gnat_get_interrupt_state (SIGBUS) != 's')
+     sigaction (SIGBUS,  &act, NULL);
 
 #if defined(__leon__) && defined(_WRS_KERNEL)
   /* Specific to the LEON VxWorks kernel run-time library */