Ada 编程/库/Ada.Exceptions

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此语言功能从 Ada 95 开始可用。

Ada.Exceptions 是自 Ada 95 以来 预定义语言环境 的一个单元。

包 Ada.Exceptions 允许您分析已捕获的异常，以关联消息引发异常或保存异常事件以供以后处理。

用法

以下示例展示了如何实现一个“最后手段”错误处理程序，它只显示与发生的错误相关的信息。

文件：numeric_6.adb (查看, 纯文本, 下载页面, 浏览所有)

with Ada.Exceptions;

procedure Numeric_6 is
  package Exept renames Ada.Exceptions;
...
           exception
              when An_Exception : others =>
                 T_IO.Put_Line
                   (Exept.Exception_Information (An_Exception));
           end Try;

规格

--                     Standard Ada library specification
--   Copyright (c) 2003-2018 Maxim Reznik <reznikmm@gmail.com>
--   Copyright (c) 2004-2016 AXE Consultants
--   Copyright (c) 2004, 2005, 2006 Ada-Europe
--   Copyright (c) 2000 The MITRE Corporation, Inc.
--   Copyright (c) 1992, 1993, 1994, 1995 Intermetrics, Inc.
--   SPDX-License-Identifier: BSD-3-Clause and LicenseRef-AdaReferenceManual
-- -------------------------------------------------------------------------

with Ada.Streams;

package Ada.Exceptions is

   pragma Preelaborate (Exceptions);

   type Exception_Id is private;
   pragma Preelaborable_Initialization (Exception_Id);

   Null_Id : constant Exception_Id;

   function Exception_Name (Id : in Exception_Id) return String;

   function Wide_Exception_Name (Id : in Exception_Id) return Wide_String;

   function Wide_Wide_Exception_Name (Id : in Exception_Id)
     return Wide_Wide_String;

   type Exception_Occurrence is limited private;
   pragma Preelaborable_Initialization (Exception_Occurrence);

   type Exception_Occurrence_Access is access all Exception_Occurrence;

   Null_Occurrence : constant Exception_Occurrence;

   procedure Raise_Exception (E       : in Exception_Id;
                              Message : in String := "");
   pragma No_Return (Raise_Exception);

   function Exception_Message (X : in Exception_Occurrence) return String;

   procedure Reraise_Occurrence (X : in Exception_Occurrence);

   function Exception_Identity (X : in Exception_Occurrence)
     return Exception_Id;

   function Exception_Name (X : in Exception_Occurrence) return String;
   --   Same as Exception_Name(Exception_Identity(X)).

   function Wide_Exception_Name (X : in Exception_Occurrence)
     return Wide_String;
   --   Same as Wide_Exception_Name(Exception_Identity(X)).

   function Wide_Wide_Exception_Name (X : in Exception_Occurrence)
     return Wide_Wide_String;
   --   Same as Wide_Wide_Exception_Name(Exception_Identity(X)).

   function Exception_Information (X : in Exception_Occurrence) return String;

   procedure Save_Occurrence (Target :    out Exception_Occurrence;
                              Source : in     Exception_Occurrence);

   function Save_Occurrence (Source : in Exception_Occurrence)
     return Exception_Occurrence_Access;

   procedure Read_Exception_Occurrence
    (Stream : not null access Ada.Streams.Root_Stream_Type'Class;
     Item   : out Exception_Occurrence);

   procedure Write_Exception_Occurrence
    (Stream : not null access Ada.Streams.Root_Stream_Type'Class;
     Item   : in Exception_Occurrence);

   for Exception_Occurrence'Read use Read_Exception_Occurrence;
   for Exception_Occurrence'Write use Write_Exception_Occurrence;

private

   pragma Import (Ada, Exception_Id);
   pragma Import (Ada, Exception_Occurrence);
   pragma Import (Ada, Null_Id);
   pragma Import (Ada, Null_Occurrence);

end Ada.Exceptions;

另请参阅

• Ada 编程/库/Ada
• Ada 编程/字符串

外部示例

• 搜索 Ada.Exceptions 的 示例：Rosetta Code, GitHub (片段), 任何 Alire 包 或 本。
• 搜索与 Ada.Exceptions 相关的 帖子：Stack Overflow, comp.lang.ada 或 任何与 Ada 相关的页面。

Ada 参考手册

Ada 95

• 11.4.1: The Package Exceptions ^{[带注释的]}

Ada 2005

• 11.4.1: The Package Exceptions ^{[带注释的]}

Ada 2012

• 11.4.1: The Package Exceptions ^{[带注释的]}

开源实现

FSF GNAT

• 规格：a-except.ads
• 主体：a-except.adb

drake

• 规格：a-except.ads
• 主体：a-except.adb