Itcl：$this变量不一致

Question

当我的项目从Tcl8.5.9/ITCL3.4迁移到Tcl8.6.6/ITCL4.0.5时，我遇到了$this变量不一致的问题，这取决于它的访问方式。下面是最小化的测试用例：

puts "Tcl  version : $tcl_patchLevel"
puts "Itcl version : [package require Itcl]"

itcl::class Base {
    public {
        method base_process {script} {
            uplevel $m_main main_process [list $script]
        }
        method set_main {main} {
          set m_main $main
        }
    }
    protected {
        variable m_main
    }
}

itcl::class Main {
  inherit Base
    public {
        method main_process {script} {
            uplevel $script
        }
    }
}

itcl::class Worker {
  inherit Base
    public {
        method worker_process_direct {} {
            puts "Direct query: this = $this"
        }
        method worker_process_inderect {} {
            base_process {puts "Indirect query: this = $this"}
        }
        method worker_process_both {} {
            puts "Direct query: this = $this"
            base_process {puts "Indirect query: this = $this"}
        }
    }
}

Main main

Worker worker
worker set_main main

puts "\n==== worker_process_direct   ===="
worker worker_process_direct

puts "\n==== worker_process_indirect ===="
worker worker_process_inderect

puts "\n==== worker_process_both     ===="
worker worker_process_both

worker_process_direct和worker_process_both函数总是提供正确的结果。但是worker_process_inderect只有在旧版本的Tcl/Itcl上才能正常工作。对于Tcl8.6.6/ITCL4.0.5，$this变量奇怪地更改为Main类的实例，而不是Worker。

下面是上面两个版本的Tcl/Itcl的脚本输出。

Tcl  version : 8.5.9
Itcl version : 3.4

==== worker_process_direct   ====
Direct query: this = ::worker

==== worker_process_indirect ====
Indirect query: this = ::worker          <<<<<<<<<<<< CORRECT

==== worker_process_both     ====
Direct query: this = ::worker
Indirect query: this = ::worker

Tcl  version : 8.6.6
Itcl version : 4.0.5

==== worker_process_direct   ====
Direct query: this = ::worker

==== worker_process_indirect ====
Indirect query: this = ::main            <<<<<<<<<< INCORRECT

==== worker_process_both     ====
Direct query: this = ::worker
Indirect query: this = ::worker

我是不是遗漏了什么，Tcl/Itcl中有一些我没有注意到的重大变化？

Answer 1

这是非常奇怪的！我将您的脚本扩充为如下定义Main：

itcl::class Main {
    inherit Base
    public {
        method main_process {script} {
            uplevel $script
            # Print what is actually going on!
            puts >>[tcl::unsupported::disassemble script $script]<<
        }
    }
}

使用8.5/3.4时，我得到以下输出：

Tcl  version : 8.5.9
Itcl version : 3.4

==== worker_process_direct   ====
Direct query: this = ::worker

==== worker_process_indirect ====
Indirect query: this = ::worker
>>ByteCode 0x0x7fedea044c10, refCt 1, epoch 3, interp 0x0x7fedea033010 (epoch 3)
  Source "puts \"Indirect query: this = $this\""
  Cmds 1, src 35, inst 12, litObjs 3, aux 0, stkDepth 3, code/src 0.00
  Commands 1:
      1: pc 0-10, src 0-34
  Command 1: "puts \"Indirect query: this = $this\""
    (0) push1 0     # "puts"
    (2) push1 1     # "Indirect query: this = "
    (4) push1 2     # "this"
    (6) loadScalarStk 
    (7) concat1 2 
    (9) invokeStk1 2 
    (11) done 
<<

==== worker_process_both     ====
Direct query: this = ::worker
Indirect query: this = ::worker
>>ByteCode 0x0x7fedea044c10, refCt 1, epoch 3, interp 0x0x7fedea033010 (epoch 3)
  Source "puts \"Indirect query: this = $this\""
  Cmds 1, src 35, inst 12, litObjs 3, aux 0, stkDepth 3, code/src 0.00
  Commands 1:
      1: pc 0-10, src 0-34
  Command 1: "puts \"Indirect query: this = $this\""
    (0) push1 0     # "puts"
    (2) push1 1     # "Indirect query: this = "
    (4) push1 2     # "this"
    (6) loadScalarStk 
    (7) concat1 2 
    (9) invokeStk1 2 
    (11) done 
<<

在8.6/4.0版本中，我得到的结果是：

Tcl  version : 8.6.3
Itcl version : 4.0.2

==== worker_process_direct   ====
Direct query: this = ::worker

==== worker_process_indirect ====
Indirect query: this = ::main
>>ByteCode 0x0x1009af010, refCt 1, epoch 136, interp 0x0x100829a10 (epoch 136)
  Source "puts \"Indirect query: this = $this"...
  Cmds 1, src 35, inst 12, litObjs 3, aux 0, stkDepth 3, code/src 0.00
  Commands 1:
      1: pc 0-10, src 0-34
  Command 1: "puts \"Indirect query: this = $this"...
    (0) push1 0     # "puts"
    (2) push1 1     # "Indirect query: this = "
    (4) push1 2     # "this"
    (6) loadStk 
    (7) strcat 2 
    (9) invokeStk1 2 
    (11) done 
<<

==== worker_process_both     ====
Direct query: this = ::worker
Indirect query: this = ::worker
>>ByteCode 0x0x1009b0210, refCt 1, epoch 136, interp 0x0x100829a10 (epoch 136)
  Source "puts \"Indirect query: this = $this"...
  Cmds 1, src 35, inst 11, litObjs 2, aux 0, stkDepth 3, code/src 0.00
  Commands 1:
      1: pc 0-9, src 0-34
  Command 1: "puts \"Indirect query: this = $this"...
    (0) push1 0     # "puts"
    (2) push1 1     # "Indirect query: this = "
    (4) loadScalar1 %v0 
    (6) strcat 2 
    (8) invokeStk1 2 
    (10) done 
<<

因此，8.5在两种(间接)情况下都使用loadScalarStk指令读取变量，而8.6在这两种情况下使用loadStk和loadScalar1来加载变量。这非常奇怪；我不希望loadScalar1出现在脚本片段中(它需要一个局部变量表)，但至少它选取了期望值，而loadStk只是选取了完全错误的值。我还尝试在两个地方使用完全相同的值-脚本保存在一个共享变量- but中，该变量产生相同的输出；它看起来像是在一个地方计算，但选择了错误的值(可能是变量解析器的问题？)而在另一种情况下，它选择了正确的值，但原因是错误的(因为LVT不应该在脚本片段中使用；这只适用于完整的过程/方法)。不管怎样，这都是个坏消息。

请在http://core.tcl-lang.org/tcl/tktnew上提交错误报告，因为这闻起来像是几种错误的行为混合在一起。