捕获前提条件 Assert_Failure

Question

我正在尝试捕获 main 过程中的这个先决条件中的错误，我想知道是否可以捕获？我是否需要将其移动到不同的过程，然后在 main 中调用它才能捕获它？

 with
    ada.text_io,
    ada.command_line,
    ada.strings.bounded,
    system.assertions;

 procedure main with
    pre => (ada.command_line.argument_count > 2)
 is
    package b_str is new
        ada.strings.bounded.generic_bounded_length (max => 255);
    use b_str;

    input_file : bounded_string;
    argument : bounded_string;
    i : integer := 1;
 begin
    while i <= ada.command_line.argument_count loop
        argument := to_bounded_string(
            ada.command_line.argument(i)
        );

         ada.text_io.put_line("[" & i'image & "] "
            & to_string(argument)
        );

        i := i + 1;
    end loop;
 exception
    when system.assertions.assert_failure =>
        ada.text_io.put_line("Failed precondition");
 end main;

Answer 1

我找到了我的答案：

Exception handlers have an important restriction that you need to be careful about: Exceptions raised in the declarative section are not caught by the handlers of that block.

发件人：https://learn.adacore.com/courses/intro-to-ada/chapters/exceptions.html

Answer 2

由于无法在声明部分处理异常，因此应将操作移动到类似于下面的包中。然后，从主过程的异常处理块中调用它。因此，您的代码不会在处理异常后终止。

with Ada.Command_line;
package Util is
    --...
    function Command_Argument_Count return Natural
         with Pre => Ada.Command_Line.Argument_Count > 2;
    --...
end Util;


--...
Exception_Handling_Block:
begin
    while i <= Util.Command_Argument_Count loop
        argument := to_bounded_string(
            ada.command_line.argument(i)
        );

        ada.text_io.put_line("[" & i'image & "] "
            & to_string(argument)
        );

        i := i + 1;
     end loop;
exception
    when system.assertions.assert_failure =>
        ada.text_io.put_line("Failed precondition");
end Exception_Handling_Block;
--...

捕获前提条件 Assert_Failure

Catch Precondition Assert_Failure

ada