在 proc 的局部变量上使用 TCL 跟踪

Question

假设我有这个 TCL 代码（这是一个简单的例子）：

proc foo {} {
   set k {0}
   foreach a { 1 2 3 4 } {
      lappend k [ expr { [lindex $k end ] + $a } ]
   }
}

我想跟踪 proc foo 中的 k 变量，就像我跟踪它一样，它是一个全局变量还是一个命名空间变量。在 TCL 8.5 中我该怎么做？
谢谢。

Answer 1

是的，甚至局部变量也可以被追踪。它不需要是静态/全局或命名空间变量。

proc trackMyVar {name element op} {
    # In case of array variable tracing, the 'element' variable will specify the array index
    # For scalar variables, it will be empty
    if {$element != ""} {
        set name ${name}($element)
    }
    upvar $name x
    if {$op eq "r"} {
        puts "Variable $name is read now. It's value : $x"
    } elseif {$op eq "w"} {
        puts "Variable $name is written now. New value : $x"
    } elseif {$op eq "u"} {
        puts "Variable $name is unset"
    } else {
        # Only remaining possible value is "a" which is for array variables 
        # For array variables, tracing will work only if they have accessed/modified with array commands
    }
}


proc foo {} {
    # Adding tracing for variable 'k'
    trace variable k rwu trackMyVar
    set k {0}
    foreach a { 1 2 3 4 } {
        lappend k [ expr { [lindex $k end ] + $a } ]
    }
    unset k; # Just added this to demonstrate 'unset' operation
}

输出

% foo
Variable k is written now. New value : 0
Variable k is read now. Its's value : 0
Variable k is written now. New value : 0 1
Variable k is read now. Its's value : 0 1
Variable k is written now. New value : 0 1 3
Variable k is read now. Its's value : 0 1 3
Variable k is written now. New value : 0 1 3 6
Variable k is read now. Its's value : 0 1 3 6
Variable k is written now. New value : 0 1 3 6 10
Variable k is unset
%

trace的命令语法如下

跟踪变量名操作命令

这里，“ops”表示感兴趣的操作，是以下一项或多项的列表

• 数组
• 阅读
• 写
• 未设置

应将其首字母指定为arwu。您可以使用任何您感兴趣的跟踪。我用过rwu。如果您只想跟踪读取操作，请在其中单独使用r。

参考：trace