From 554fd8c5195424bdbcabf5de30fdc183aba391bd Mon Sep 17 00:00:00 2001 From: upstream source tree Date: Sun, 15 Mar 2015 20:14:05 -0400 Subject: obtained gcc-4.6.4.tar.bz2 from upstream website; verified gcc-4.6.4.tar.bz2.sig; imported gcc-4.6.4 source tree from verified upstream tarball. downloading a git-generated archive based on the 'upstream' tag should provide you with a source tree that is binary identical to the one extracted from the above tarball. if you have obtained the source via the command 'git clone', however, do note that line-endings of files in your working directory might differ from line-endings of the respective files in the upstream repository. --- gcc/ada/s-shasto.ads | 183 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 183 insertions(+) create mode 100644 gcc/ada/s-shasto.ads (limited to 'gcc/ada/s-shasto.ads') diff --git a/gcc/ada/s-shasto.ads b/gcc/ada/s-shasto.ads new file mode 100644 index 000000000..0ef65cc59 --- /dev/null +++ b/gcc/ada/s-shasto.ads @@ -0,0 +1,183 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT COMPILER COMPONENTS -- +-- -- +-- S Y S T E M . S H A R E D _ S T O R A G E -- +-- -- +-- S p e c -- +-- -- +-- Copyright (C) 1998-2009, Free Software Foundation, Inc. -- +-- -- +-- GNAT is free software; you can redistribute it and/or modify it under -- +-- terms of the GNU General Public License as published by the Free Soft- -- +-- ware Foundation; either version 3, or (at your option) any later ver- -- +-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- +-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- +-- or FITNESS FOR A PARTICULAR PURPOSE. -- +-- -- +-- As a special exception under Section 7 of GPL version 3, you are granted -- +-- additional permissions described in the GCC Runtime Library Exception, -- +-- version 3.1, as published by the Free Software Foundation. -- +-- -- +-- You should have received a copy of the GNU General Public License and -- +-- a copy of the GCC Runtime Library Exception along with this program; -- +-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- +-- . -- +-- -- +-- GNAT was originally developed by the GNAT team at New York University. -- +-- Extensive contributions were provided by Ada Core Technologies Inc. -- +-- -- +------------------------------------------------------------------------------ + +-- This package manages the shared/persistent storage required for +-- full implementation of variables in Shared_Passive packages, more +-- precisely variables whose enclosing dynamic scope is a shared +-- passive package. This implementation is specific to GNAT and GLADE +-- provides a more general implementation not dedicated to file +-- storage. + +-- This unit (and shared passive partitions) are supported on all +-- GNAT implementations except on OpenVMS (where problems arise from +-- trying to share files, and with version numbers of files) + +-- -------------------------- +-- -- Shared Storage Model -- +-- -------------------------- + +-- The basic model used is that each partition that references the +-- Shared_Passive package has a local copy of the package data that +-- is initialized in accordance with the declarations of the package +-- in the normal manner. The routines in System.Shared_Storage are +-- then used to ensure that the values in these separate copies are +-- properly synchronized with the state of the overall system. + +-- In the GNAT implementation, this synchronization is ensured by +-- maintaining a set of files, in a designated directory. The +-- directory is designated by setting the environment variable +-- SHARED_MEMORY_DIRECTORY. This variable must be set for all +-- partitions. If the environment variable is not defined, then the +-- current directory is used. + +-- There is one storage for each variable. The name is the fully +-- qualified name of the variable with all letters forced to lower +-- case. For example, the variable Var in the shared passive package +-- Pkg results in the storage name pkg.var. + +-- If the storage does not exist, it indicates that no partition has +-- assigned a new value, so that the initial value is the correct +-- one. This is the critical component of the model. It means that +-- there is no system-wide synchronization required for initializing +-- the package, since the shared storages need not (and do not) +-- reflect the initial state. There is therefore no issue of +-- synchronizing initialization and read/write access. + +-- ----------------------- +-- -- Read/Write Access -- +-- ----------------------- + +-- The approach is as follows: + +-- For each shared variable, var, an instantiation of the below generic +-- package is created which provides Read and Write supporting procedures. + +-- The routine Read in package System.Shared_Storage.Shared_Var_Procs +-- ensures to assign variable V to the last written value among processes +-- referencing it. A call to this procedure is generated by the expander +-- before each read access to the shared variable. + +-- The routine Write in package System.Shared_Storage.Shared_Var_Proc +-- set a new value to the shared variable and, according to the used +-- implementation, propagate this value among processes referencing it. +-- A call to this procedure is generated by the expander after each +-- assignment of the shared variable. + +-- Note: a special circuit allows the use of stream attributes Read and +-- Write for limited types (using the corresponding attribute for the +-- full type), but there are limitations on the data that can be placed +-- in shared passive partitions. See sem_smem.ads/adb for details. + +-- ---------------------------------------------------------------- +-- -- Handling of Protected Objects in Shared Passive Partitions -- +-- ---------------------------------------------------------------- + +-- In the context of GNAT, during the execution of a protected +-- subprogram call, access is locked out using a locking mechanism +-- per protected object, as provided by the GNAT.Lock_Files +-- capability in the specific case of GNAT. This package contains the +-- lock and unlock calls, and the expander generates a call to the +-- lock routine before the protected call and a call to the unlock +-- routine after the protected call. + +-- Within the code of the protected subprogram, the access to the +-- protected object itself uses the local copy, without any special +-- synchronization. Since global access is locked out, no other task +-- or partition can attempt to read or write this data as long as the +-- lock is held. + +-- The data in the local copy does however need synchronizing with +-- the global values in the shared storage. This is achieved as +-- follows: + +-- The protected object generates a read and assignment routine as +-- described for other shared passive variables. The code for the +-- 'Read and 'Write attributes (not normally allowed, but allowed +-- in this special case) simply reads or writes the values of the +-- components in the protected record. + +-- The lock call is followed by a call to the shared read routine to +-- synchronize the local copy to contain the proper global value. + +-- The unlock call in the procedure case only is preceded by a call +-- to the shared assign routine to synchronize the global shared +-- storages with the (possibly modified) local copy. + +-- These calls to the read and assign routines, as well as the lock +-- and unlock routines, are inserted by the expander (see exp_smem.adb). + +package System.Shared_Storage is + + procedure Shared_Var_Lock (Var : String); + -- This procedure claims the shared storage lock. It is used for + -- protected types in shared passive packages. A call to this + -- locking routine is generated as the first operation in the code + -- for the body of a protected subprogram, and it busy waits if + -- the lock is busy. + + procedure Shared_Var_Unlock (Var : String); + -- This procedure releases the shared storage lock obtained by a + -- prior call to the Shared_Var_Lock procedure, and is to be + -- generated as the last operation in the body of a protected + -- subprogram. + + -- This generic package is instantiated for each shared passive + -- variable. It provides supporting procedures called upon each + -- read or write access by the expanded code. + + generic + + type Typ is limited private; + -- Shared passive variable type + + V : in out Typ; + -- Shared passive variable + + Full_Name : String; + -- Shared passive variable storage name + + package Shared_Var_Procs is + + procedure Read; + -- Shared passive variable access routine. Each reference to the + -- shared variable, V, is preceded by a call to the corresponding + -- Read procedure, which either leaves the initial value unchanged + -- if the storage does not exist, or reads the current value from + -- the shared storage. + + procedure Write; + -- Shared passive variable assignment routine. Each assignment to + -- the shared variable, V, is followed by a call to the corresponding + -- Write procedure, which writes the new value to the shared storage. + + end Shared_Var_Procs; + +end System.Shared_Storage; -- cgit v1.2.3