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Tcl Throw Error


If it reaches the top level of script evaluation in tclsh, it will be printed on the console before, in the non-interactive case, causing an exit (the behavior in other programs return is usually considered to mean, "return from the current call", but what it actually means is "return to the interpreter some information about a level, which in the common case Description editGenerates an error with the specified message. The mechanism by which these options work is described in more detail below. -options options The value options must be a valid dictionary. have a peek here

The stack will be unwound until the error is trapped by a suitable catch or try command. When in doubt, just use error.Show discussionDKF: I find that it is best to use error (or throw) when it is an internal problem of the code, and return -code error The level value must be a non-negative integer representing a number of levels on the call stack. Procedure invocation provides special treatment when evaluation of the procedure body returns the return code TCL_RETURN.

Tcl Error Handling

Tcl's initial error stack will include only the call to the procedure, and stack unwinding will append information about higher stack levels, but there will be no information about the context If the info argument is provided and is non-empty, it is used to initialize the global variable errorInfo. It is certainly better to fix problems the first time they appear, but tinkering with the code on a live system is rather poor practice.Most users would rather not have the

The caller of catch may then use this information, including values such as -code and -level in $optionsVarname, for its own purposes. return can be considered a sort of restricted uplevel that provides a flexible mechanism for expressing various runtime conditions. The catch command may be used to capture all of this information -- the return code, the result, and the return options dictionary -- that arise from evaluation of a script. Tcl Error Code If the problem is in your caller (e.g., because they gave you bad arguments) then use return -code error.

So in C, you have to add checks for everything that might go wrong; in Tcl, you only need to treat errors if you can express it better than Tcl already Tcl Throw Example At most one handler clause will selected. Each element is a list, with the * last element being the most current one. */ typedef struct { Tcl_Obj * errorCodeStack; Tcl_Obj * errorInfoStack; Tcl_Obj * errorMsgStack; Tcl_Obj * errorCodeName; pop over to these guys EXAMPLES The following produces an error that is identical to that produced by expr when trying to divide a value by zero.

Join 80 other followers Categories Admin (2) Cool (26) Family (4) Finance (1) Food (1) Gadget (8) Humor (2) Internet (25) Interview (7) IOS (3) Journal (11) Misc (1) Opinion (10) Tcl Warning This feature is most useful in conjunction with the catch command: if a caught error cannot be handled successfully, info can be used to return a stack trace reflecting the original If no -errorinfo option is provided to return when the -code error option is provided, Tcl will provide its own initial stack trace value in the entry for -errorinfo. RETURN OPTIONS In addition to a result and a return code, evaluation of a command in Tcl also produces a dictionary of return options.

Tcl Throw Example

If an error is rethrown within a catch block, the existing stack trace will be preserved with the rethrown error. http://www.tcl.tk/cgi-bin/tct/tip/89.html The syntax for each of these commands is shown below. Tcl Error Handling Send to Email Address Your Name Your Email Address Cancel Post was not sent - check your email addresses! Tcl Error Command If one or more catch blocks are specified, each corresponding body represents a required block of code that is evaluated if the resulting errorCode matches the type condition.

All Rights Reserved. http://colinmeldrum.com/tcl-error/tcl-error-f5.html The return -code command acts similarly within script files that are evaluated by the source command. In the usual case where the -code option is not specified the procedure will return normally. break (or 3) The return code of the procedure is 3 (TCL_BREAK). Tcl Return Error

What is Tk? It is also evaluated if a throw statement occurs within the catch clause. The error created is described by the type and message arguments: type must contain a list of words describing the error in a form that is machine-readable (and which will form http://colinmeldrum.com/tcl-error/tcl-last-error.html In Tcl, they're like "little friends" - helpful (explaining the problem), not messing up everything (as a Segmentation Fault/Bus Error/Divide by Zero would do).

Some of Tcl's built-in commands evaluate scripts as part of their functioning. Tcl Catch Example Documentation edithttp://www.tcl.tk/man/tcl/TclCmd/catch.htmOfficial reference.TIP 90, Enable return -code in Control Structure ProcsIncludes a good description of the operation of catch. try body ?catch {{type_list} ?ecvar? ?msgvar? ?infovar?} body ...? ?finally body?

This is the mechanism by which errors during script evaluation cause an interruption and unwinding of the call stack.

Note, catch {*}, if specified, will catch all remaining errors. I'm now leaning towards replacing the above idiom with the following:if {1 == [catch { #somescript } result_or_errormsg]} { #handle error } else { #normal processing }This suffers from the problem An example for simple error handling is shown below − #!/usr/bin/tclsh proc Div {a b} { if {$b == 0} { error "Error generated by error" "Info String for error" 401 Tcl Try Catch Example proc myBreak {} { return -code break } With the -level 0 option, return itself can serve as a replacement for break, with the help of interp alias.

These commands, if implemented into the core, will be useful for any script currently using the catch construct. config -cursor arrow } try - catch - catch try { ;# Some code that will cause an error } catch {{POSIX *} eCode eMessage} { ;# Statements to handle POSIX return ?-code code? ?result? http://colinmeldrum.com/tcl-error/tcl-tk-error.html Reference Implementation /* * Implementation of try/catch and throw commands according to TIP 89 */ #include /* * We keep a stack of contexts; whenever we have to handle an