我设法将此问题减少到：
program Project1;
{$APPTYPE CONSOLE}
uses
SysUtils,Threading;
procedure Foo(AString: string);
var
LTask : ITask;
capturedString : string;
procedure nested;
begin
try
WriteLn('nested : ' + capturedString); { ! EIntOverflow (Win32) here }
except on E : Exception do
WriteLn(E.Message);
end;
end;
begin
capturedString := AString;
WriteLn('Local : ' + capturedString);
nested;
LTask := TTask.Create(
procedure
procedure Anonnested;
begin
WriteLn(capturedString); { Removing this eliminates the problem }
end;
begin
end);
end;
begin
Foo('foo');
ReadLn;
end.
从嵌套方法中访问时,captureString变量在这里被破坏. Win32编译引发EIntOverflow,Win64编译写出一个(损坏的)空字符串 – 可以通过某种操作将构建引入AV或其他异常,但在所有情况下,在进入嵌套过程时对本地变量的引用都会被破坏.
这似乎只有在闭包中捕获captureString时才会发生.
出了什么问题？
解决方法
这似乎是一个编译器错误：
#RSP-18833: Capture by closure corrupts local variable used in nested method
解决方法是在匿名方法中使用第二个变量进行捕获：
procedure Foo(AString: string);
var
LTask : ITask;
capturedString,s2 : string;
procedure nested;
begin
try
WriteLn('nested : ' + capturedString);
except on E : Exception do
WriteLn(E.Message); { !!! }
end;
end;
begin
capturedString := AString;
s2 := capturedString;
WriteLn('Local : ' + capturedString);
nested;
LTask := TTask.Create(
procedure
procedure Anonnested;
begin
WriteLn(s2); { Capture another variable }
end;
begin
end);
end;