Itcl：$this 变量不一致

Question

在将我的项目从 Tcl 8.5.9/Itcl 3.4 迁移到 Tcl 8.6.6/Itcl 4.0.5 时，我遇到了 $this 变量的不一致问题，具体取决于它的访问方式。这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 函数始终提供正确的结果。但worker_process_inderect 仅适用于旧版本的 Tcl/Itcl。对于 Tcl 8.6.6/Itcl 4.0.5，$this 变量奇怪地更改为 Main 类的实例，而不是 Worker。

这是上面两个版本的 Tcl/Itcl 脚本的输出。

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

我是否遗漏了什么，并且 Tcl/Itcl 发生了我没有注意到的重大变化？

Answer 1

现在这非常很好奇！我扩充了你的脚本来定义Main，如下所示：

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

在 8.5/3.4 中，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 
<<

使用 8.6/4.0 我得到了这个：

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 使用loadScalarStk 指令在两种（间接）情况下读取变量，而 8.6 使用loadStk 和loadScalar1 在两种情况下加载变量。这很奇怪；我不希望 loadScalar1 出现在脚本片段中（它需要一个局部变量表），但至少它正在获取预期值，而 loadStk 只是完全获取了错误的值。我也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中——但这会产生相同的输出；看起来在一个地方它正在评估但选择了错误的值（可能是变量解析器问题？），而在另一个地方它正在选择正确的值但出于错误的原因（因为 LVT 不应该用于脚本片段；这仅适用于完整的过程/方法）。不管怎样，这都是坏消息。

请在http://core.tcl-lang.org/tcl/tktnew 提交错误报告，因为这听起来像是多种错误行为的混合。