diff options
Diffstat (limited to 'gcc/ada/a-exexpr.adb')
| -rw-r--r-- | gcc/ada/a-exexpr.adb | 100 |
1 files changed, 70 insertions, 30 deletions
diff --git a/gcc/ada/a-exexpr.adb b/gcc/ada/a-exexpr.adb index 0d0eb09..41fb21d 100644 --- a/gcc/ada/a-exexpr.adb +++ b/gcc/ada/a-exexpr.adb @@ -106,7 +106,7 @@ package body Exception_Propagation is type Unwind_Word is mod 2 ** System.Word_Size; for Unwind_Word'Size use System.Word_Size; - -- Map the corresponding C type used in Unwind_Exception below. + -- Map the corresponding C type used in Unwind_Exception below type Unwind_Exception is record Class : Exception_Class := GNAT_Exception_Class; @@ -114,46 +114,36 @@ package body Exception_Propagation is Private1 : Unwind_Word; Private2 : Unwind_Word; end record; - -- Map the GCC struct used for exception handling. + -- Map the GCC struct used for exception handling for Unwind_Exception'Alignment use Standard'Maximum_Alignment; -- The C++ ABI mandates the common exception header to be at least -- doubleword aligned, and the libGCC implementation actually makes it - -- maximally aligned (see unwind.h). We need to match this because: - - -- 1/ We pass pointers to such headers down to the underlying - -- libGCC unwinder, - - -- and - - -- 2/ The GNAT_GCC_Exception record below starts with this common - -- common header and has a C counterpart which needs to be laid - -- out identically in raise.c. If the alignment of the C and Ada - -- common headers mismatch, their size may also differ, and the - -- layouts may not match anymore. + -- maximally aligned (see unwind.h). See additional comments on the + -- alignment below. --------------------------------------------------------------- -- GNAT specific entities to deal with the GCC eh circuitry -- --------------------------------------------------------------- -- A GNAT exception object to be dealt with by the personality routine - -- called by the GCC unwinding runtime. This structure shall match the - -- one in raise.c and is currently experimental as it might be merged - -- with the GNAT runtime definition some day. + -- called by the GCC unwinding runtime. type GNAT_GCC_Exception is record Header : Unwind_Exception; -- ABI Exception header first. Id : Exception_Id; - -- GNAT Exception identifier. This is used by the personality - -- routine to determine if the context it examines contains a - -- handler for the exception beeing propagated. + -- GNAT Exception identifier. This is filled by Propagate_Exception + -- and then used by the personality routine to determine if the context + -- it examines contains a handler for the exception beeing propagated. N_Cleanups_To_Trigger : Integer; - -- Number of cleanup only frames encountered in SEARCH phase. - -- This is used to control the forced unwinding triggered when - -- no handler has been found. + -- Number of cleanup only frames encountered in SEARCH phase. This is + -- initialized to 0 by Propagate_Exception and maintained by the + -- personality routine to control a forced unwinding phase triggering + -- all the cleanups before calling Unhandled_Exception_Terminate when + -- an exception is not handled. Next_Exception : EOA; -- Used to create a linked list of exception occurrences. @@ -161,6 +151,23 @@ package body Exception_Propagation is pragma Convention (C, GNAT_GCC_Exception); + -- There is a subtle issue with the common header alignment, since the C + -- version is aligned on BIGGEST_ALIGNMENT, the Ada version is aligned on + -- Standard'Maximum_Alignment, and those two values don't quite represent + -- the same concepts and so may be decoupled someday. One typical reason + -- is that BIGGEST_ALIGNMENT may be larger than what the underlying system + -- allocator guarantees, and there are extra costs involved in allocating + -- objects aligned to such factors. + + -- To deal with the potential alignment differences between the C and Ada + -- representations, the Ada part of the whole structure is only accessed + -- by the personality routine through the accessors declared below. Ada + -- specific fields are thus always accessed through consistent layout, and + -- we expect the actual alignment to always be large enough to avoid traps + -- from the C accesses to the common header. Besides, accessors aleviate + -- the need for a C struct whole conterpart, both painful and errorprone + -- to maintain anyway. + type GNAT_GCC_Exception_Access is access all GNAT_GCC_Exception; function To_GNAT_GCC_Exception is new @@ -251,6 +258,15 @@ package body Exception_Propagation is function Import_Code_For (E : Exception_Data_Ptr) return Exception_Code; pragma Export (C, Import_Code_For, "__gnat_import_code_for"); + function EID_For (GNAT_Exception : GNAT_GCC_Exception_Access) + return Exception_Id; + pragma Export (C, EID_For, "__gnat_eid_for"); + + procedure Adjust_N_Cleanups_For + (GNAT_Exception : GNAT_GCC_Exception_Access; + Adjustment : Integer); + pragma Export (C, Adjust_N_Cleanups_For, "__gnat_adjust_n_cleanups_for"); + ------------ -- Remove -- ------------ @@ -457,6 +473,7 @@ package body Exception_Propagation is -- already been performed by Propagate_Exception. This hook remains for -- potential future necessity in optimizing the overall scheme, as well -- a useful debugging tool. + null; end Begin_Handler; @@ -466,7 +483,6 @@ package body Exception_Propagation is procedure End_Handler (GCC_Exception : GNAT_GCC_Exception_Access) is Removed : Boolean; - begin Removed := Remove (Get_Current_Excep.all, GCC_Exception); pragma Assert (Removed); @@ -553,6 +569,30 @@ package body Exception_Propagation is Unhandled_Exception_Terminate; end Propagate_Exception; + --------------------------- + -- Adjust_N_Cleanups_For -- + --------------------------- + + procedure Adjust_N_Cleanups_For + (GNAT_Exception : GNAT_GCC_Exception_Access; + Adjustment : Integer) + is + begin + GNAT_Exception.N_Cleanups_To_Trigger := + GNAT_Exception.N_Cleanups_To_Trigger + Adjustment; + end Adjust_N_Cleanups_For; + + ------------- + -- EID_For -- + ------------- + + function EID_For + (GNAT_Exception : GNAT_GCC_Exception_Access) return Exception_Id + is + begin + return GNAT_Exception.Id; + end EID_For; + --------------------- -- Import_Code_For -- --------------------- @@ -612,29 +652,29 @@ package body Exception_Propagation is -- An attempt was made to use the Private_Data pointer for this purpose. -- It did not work because: - -- 1/ The Private_Data has to be saved by Save_Occurrence to be usable + -- 1) The Private_Data has to be saved by Save_Occurrence to be usable -- as a key in case of a later reraise, - -- 2/ There is no easy way to synchronize End_Handler for an occurrence + -- 2) There is no easy way to synchronize End_Handler for an occurrence -- and the data attached to potential copies, so these copies may end -- up pointing to stale data. Moreover ... - -- 3/ The same address may be reused for different occurrences, which + -- 3) The same address may be reused for different occurrences, which -- defeats the idea of using it as a key. -- The example below illustrates: -- Saved_CE : Exception_Occurrence; - -- + -- begin -- raise Constraint_Error; -- exception -- when CE: others => -- Save_Occurrence (Saved_CE, CE); <= Saved_CE.PDA = CE.PDA -- end; - -- + -- <= Saved_CE.PDA is stale (!) - -- + -- begin -- raise Program_Error; <= Saved_CE.PDA = PE.PDA (!!) -- exception |