233 lines
11 KiB
Diff
233 lines
11 KiB
Diff
From c5a03de594d6bb6ea5012a6549404e4631c903c8 Mon Sep 17 00:00:00 2001
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From: Alexandre Oliva <oliva@adacore.com>
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Date: Wed, 9 Aug 2023 16:57:31 +0200
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Subject: [PATCH] crossgcc: Backport GNAT exception handler v1 patch
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Signed-off-by: Adrien Bourmault <neox@gnu.org>
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---
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.../patches/gcc-8.3.0_gnat_eh_new.patch | 212 ++++++++++++++++++
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1 file changed, 212 insertions(+)
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create mode 100644 util/crossgcc/patches/gcc-8.3.0_gnat_eh_new.patch
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diff --git a/util/crossgcc/patches/gcc-8.3.0_gnat_eh_new.patch b/util/crossgcc/patches/gcc-8.3.0_gnat_eh_new.patch
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new file mode 100644
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index 00000000..75e4f18d
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--- /dev/null
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+++ b/util/crossgcc/patches/gcc-8.3.0_gnat_eh_new.patch
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@@ -0,0 +1,212 @@
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+diff --git a/gcc/ada/libgnat/a-exexpr.adb b/gcc/ada/libgnat/a-exexpr.adb
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+index b1aa1c6e6ba..5e72fd6e3f2 100644
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+--- a/gcc/ada/libgnat/a-exexpr.adb
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++++ b/gcc/ada/libgnat/a-exexpr.adb
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+@@ -197,15 +197,75 @@ package body Exception_Propagation is
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+ -- whose machine occurrence is Mo. The message is empty, the backtrace
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+ -- is empty too and the exception identity is Foreign_Exception.
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+
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+- -- Hooks called when entering/leaving an exception handler for a given
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+- -- occurrence, aimed at handling the stack of active occurrences. The
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+- -- calls are generated by gigi in tree_transform/N_Exception_Handler.
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++ -- Hooks called when entering/leaving an exception handler for a
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++ -- given occurrence. The calls are generated by gigi in
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++ -- Exception_Handler_to_gnu_gcc.
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++
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++ -- Begin_Handler_v1, called when entering an exception handler,
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++ -- claims responsibility for the handler to release the
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++ -- GCC_Exception occurrence. End_Handler_v1, called when
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++ -- leaving the handler, releases the occurrence, unless the
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++ -- occurrence is propagating further up, or the handler is
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++ -- dynamically nested in the context of another handler that
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++ -- claimed responsibility for releasing that occurrence.
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++
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++ -- Responsibility is claimed by changing the Cleanup field to
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++ -- Claimed_Cleanup, which enables claimed exceptions to be
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++ -- recognized, and avoids accidental releases even by foreign
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++ -- handlers.
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++
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++ function Begin_Handler_v1
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++ (GCC_Exception : not null GCC_Exception_Access)
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++ return System.Address;
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++ pragma Export (C, Begin_Handler_v1, "__gnat_begin_handler_v1");
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++ -- Called when entering an exception handler. Claim
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++ -- responsibility for releasing GCC_Exception, by setting the
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++ -- cleanup/release function to Claimed_Cleanup, and return the
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++ -- address of the previous cleanup/release function.
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++
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++ procedure End_Handler_v1
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++ (GCC_Exception : not null GCC_Exception_Access;
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++ Saved_Cleanup : System.Address;
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++ Propagating_Exception : GCC_Exception_Access);
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++ pragma Export (C, End_Handler_v1, "__gnat_end_handler_v1");
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++ -- Called when leaving an exception handler. Restore the
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++ -- Saved_Cleanup in the GCC_Exception occurrence, and then release
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++ -- it, unless it remains claimed by an enclosing handler, or
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++ -- GCC_Exception and Propagating_Exception are the same
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++ -- occurrence. Propagating_Exception could be either an
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++ -- occurrence (re)raised within the handler of GCC_Exception, when
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++ -- we're executing as an exceptional cleanup, or null, if we're
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++ -- completing the handler of GCC_Exception normally.
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++
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++ procedure Claimed_Cleanup
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++ (Reason : Unwind_Reason_Code;
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++ GCC_Exception : not null GCC_Exception_Access);
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++ pragma Export (C, Claimed_Cleanup, "__gnat_claimed_cleanup");
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++ -- A do-nothing placeholder installed as GCC_Exception.Cleanup
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++ -- while handling GCC_Exception, to claim responsibility for
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++ -- releasing it, and to stop it from being accidentally released.
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++
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++ -- The following are version 0 implementations of the version 1
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++ -- hooks above. They remain in place for compatibility with the
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++ -- output of compilers that still use version 0, such as those
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++ -- used during bootstrap. They are interoperable with the v1
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++ -- hooks, except that the older versions may malfunction when
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++ -- handling foreign exceptions passed to Reraise_Occurrence.
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+
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+ procedure Begin_Handler (GCC_Exception : not null GCC_Exception_Access);
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+ pragma Export (C, Begin_Handler, "__gnat_begin_handler");
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++ -- Called when entering an exception handler translated by an old
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++ -- compiler. It does nothing.
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+
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+ procedure End_Handler (GCC_Exception : GCC_Exception_Access);
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+ pragma Export (C, End_Handler, "__gnat_end_handler");
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++ -- Called when leaving an exception handler translated by an old
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++ -- compiler. It releases GCC_Exception, unless it is null. It is
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++ -- only ever null when the handler has a 'raise;' translated by a
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++ -- v0-using compiler. The artificial handler variable passed to
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++ -- End_Handler was set to null to tell End_Handler to refrain from
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++ -- releasing the reraised exception. In v1 safer ways are used to
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++ -- accomplish that.
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+
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+ --------------------------------------------------------------------
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+ -- Accessors to Basic Components of a GNAT Exception Data Pointer --
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+@@ -352,6 +412,128 @@ package body Exception_Propagation is
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+ end if;
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+ end Setup_Current_Excep;
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+
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++ ----------------------
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++ -- Begin_Handler_v1 --
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++ ----------------------
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++
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++ function Begin_Handler_v1
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++ (GCC_Exception : not null GCC_Exception_Access)
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++ return System.Address is
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++ Saved_Cleanup : constant System.Address := GCC_Exception.Cleanup;
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++ begin
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++ -- Claim responsibility for releasing this exception, and stop
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++ -- others from releasing it.
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++ GCC_Exception.Cleanup := Claimed_Cleanup'Address;
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++ return Saved_Cleanup;
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++ end Begin_Handler_v1;
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++
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++ --------------------
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++ -- End_Handler_v1 --
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++ --------------------
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++
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++ procedure End_Handler_v1
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++ (GCC_Exception : not null GCC_Exception_Access;
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++ Saved_Cleanup : System.Address;
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++ Propagating_Exception : GCC_Exception_Access) is
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++ begin
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++ GCC_Exception.Cleanup := Saved_Cleanup;
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++ -- Restore the Saved_Cleanup, so that it is either used to
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++ -- release GCC_Exception below, or transferred to the next
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++ -- handler of the Propagating_Exception occurrence. The
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++ -- following test ensures that an occurrence is only released
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++ -- once, even after reraises.
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++ --
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++ -- The idea is that the GCC_Exception is not to be released
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++ -- unless it had an unclaimed Cleanup when the handler started
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++ -- (see Begin_Handler_v1 above), but if we propagate across its
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++ -- handler a reraise of the same exception, we transfer to the
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++ -- Propagating_Exception the responsibility for running the
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++ -- Saved_Cleanup when its handler completes.
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++ --
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++ -- This ownership transfer mechanism ensures safety, as in
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++ -- single release and no dangling pointers, because there is no
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++ -- way to hold on to the Machine_Occurrence of an
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++ -- Exception_Occurrence: the only situations in which another
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++ -- Exception_Occurrence gets the same Machine_Occurrence are
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++ -- through Reraise_Occurrence, and plain reraise, and so we
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++ -- have the following possibilities:
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++ --
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++ -- - Reraise_Occurrence is handled within the running handler,
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++ -- and so when completing the dynamically nested handler, we
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++ -- must NOT release the exception. A Claimed_Cleanup upon
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++ -- entry of the nested handler, installed when entering the
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++ -- enclosing handler, ensures the exception will not be
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++ -- released by the nested handler, but rather by the enclosing
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++ -- handler.
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++ --
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++ -- - Reraise_Occurrence/reraise escapes the running handler,
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++ -- and we run as an exceptional cleanup for GCC_Exception. The
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++ -- Saved_Cleanup was reinstalled, but since we're propagating
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++ -- the same machine occurrence, we do not release it. Instead,
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++ -- we transfer responsibility for releasing it to the eventual
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++ -- handler of the propagating exception.
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++ --
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++ -- - An unrelated exception propagates through the running
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++ -- handler. We restored GCC_Exception.Saved_Cleanup above.
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++ -- Since we're propagating a different exception, we proceed to
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++ -- release GCC_Exception, unless Saved_Cleanup was
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++ -- Claimed_Cleanup, because then we know we're not in the
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++ -- outermost handler for GCC_Exception.
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++ --
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++ -- - The handler completes normally, so it reinstalls the
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++ -- Saved_Cleanup and runs it, unless it was Claimed_Cleanup.
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++ -- If Saved_Cleanup is null, Unwind_DeleteException (currently)
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++ -- has no effect, so we could skip it, but if it is ever
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++ -- changed to do more in this case, we're ready for that,
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++ -- calling it exactly once.
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++ if Saved_Cleanup /= Claimed_Cleanup'Address
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++ and then
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++ Propagating_Exception /= GCC_Exception
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++ then
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++ declare
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++ Current : constant EOA := Get_Current_Excep.all;
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++ Cur_Occ : constant GCC_Exception_Access
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++ := To_GCC_Exception (Current.Machine_Occurrence);
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++ begin
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++ -- If we are releasing the Machine_Occurrence of the current
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++ -- exception, reset the access to it, so that it is no
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++ -- longer accessible.
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++ if Cur_Occ = GCC_Exception then
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++ Current.Machine_Occurrence := System.Null_Address;
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++ end if;
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++ end;
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++ Unwind_DeleteException (GCC_Exception);
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++ end if;
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++ end End_Handler_v1;
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++
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++ ---------------------
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++ -- Claimed_Cleanup --
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++ ---------------------
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++
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++ procedure Claimed_Cleanup
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++ (Reason : Unwind_Reason_Code;
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++ GCC_Exception : not null GCC_Exception_Access) is
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++ pragma Unreferenced (Reason);
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++ pragma Unreferenced (GCC_Exception);
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++ begin
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++ -- This procedure should never run. If it does, it's either a
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++ -- version 0 handler or a foreign handler, attempting to
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++ -- release an exception while a version 1 handler that claimed
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++ -- responsibility for releasing the exception remains still
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++ -- active. This placeholder stops GCC_Exception from being
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++ -- released by them.
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++
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++ -- We could get away with just Null_Address instead, with
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++ -- nearly the same effect, but with this placeholder we can
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++ -- detect and report unexpected releases, and we can tell apart
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++ -- a GCC_Exception without a Cleanup, from one with another
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++ -- active handler, so as to still call Unwind_DeleteException
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++ -- exactly once: currently, Unwind_DeleteException does nothing
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++ -- when the Cleanup is null, but should it ever be changed to
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++ -- do more, we'll still be safe.
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++ null;
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++ end Claimed_Cleanup;
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++
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+ -------------------
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+ -- Begin_Handler --
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+ -------------------
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--
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2.30.2
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