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Diffstat (limited to 'doc')
| -rw-r--r-- | doc/interp.n | 158 |
1 files changed, 79 insertions, 79 deletions
diff --git a/doc/interp.n b/doc/interp.n index 8b32ee0..618233c 100644 --- a/doc/interp.n +++ b/doc/interp.n @@ -5,7 +5,7 @@ '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" -'\" RCS: @(#) $Id: interp.n,v 1.27 2007/02/18 18:42:54 dkf Exp $ +'\" RCS: @(#) $Id: interp.n,v 1.28 2007/08/19 10:26:01 dkf Exp $ '\" .so man.macros .TH interp n 7.6 Tcl "Tcl Built-In Commands" @@ -660,97 +660,97 @@ command, by making the current namespace be different from the global one. .SH "RESOURCE LIMITS" .VS 8.5 .PP -Every interpreter has two kinds of resource limits that may be imposed -by any master interpreter upon its slaves. Command limits (of type -\fBcommand\fR) restrict the total number of Tcl commands that may be -executed by an interpreter (as can be inspected via the \fBinfo -cmdcount\fR command), and time limits (of type \fBtime\fR) place a -limit by which execution within the interpreter must complete. -.PP -When a limit is exceeded for an interpreter, first any handler -callbacks defined by master interpreters are called. If those -callbacks increase or remove the limit, execution within the -(previously) limited interpreter continues. If the limit is still in -force, an error is generated at that point and normal processing of -errors within the interpreter (by the \fBcatch\fR command) is -disabled, so the error propagates outwards (building a stack-trace as -it goes) to the point where the limited interpreter was invoked -(e.g. by \fBinterp eval\fR) where it becomes the responsibility of the -calling code to catch and handle. -.PP -Every limit has a number of options associated with it, some of which -are common across all kinds of limits, and others of which are -particular to the kind of limit. +Every interpreter has two kinds of resource limits that may be imposed by any +master interpreter upon its slaves. Command limits (of type \fBcommand\fR) +restrict the total number of Tcl commands that may be executed by an +interpreter (as can be inspected via the \fBinfo cmdcount\fR command), and +time limits (of type \fBtime\fR) place a limit by which execution within the +interpreter must complete. Note that time limits are expressed as +\fIabsolute\fR times (as in \fBclock seconds\fR) and not relative times (as in +\fBafter\fR) because they may be modified after creation. +.PP +When a limit is exceeded for an interpreter, first any handler callbacks +defined by master interpreters are called. If those callbacks increase or +remove the limit, execution within the (previously) limited interpreter +continues. If the limit is still in force, an error is generated at that point +and normal processing of errors within the interpreter (by the \fBcatch\fR +command) is disabled, so the error propagates outwards (building a stack-trace +as it goes) to the point where the limited interpreter was invoked (e.g. by +\fBinterp eval\fR) where it becomes the responsibility of the calling code to +catch and handle. +.SS "LIMIT OPTIONS" +.PP +Every limit has a number of options associated with it, some of which are +common across all kinds of limits, and others of which are particular to the +kind of limit. .TP \fB\-command\fR -This option (common for all limit types) specifies (if non-empty) a -Tcl script to be executed in the global namespace of the interpreter -reading and writing the option when the particular limit in the -limited interpreter is exceeded. The callback may modify the limit on -the interpreter if it wishes the limited interpreter to continue -executing. If the callback generates an error, it is reported through -the background error mechanism (see \fBBACKGROUND ERROR HANDLING\fR). -Note that the -callbacks defined by one interpreter are completely isolated from the -callbacks defined by another, and that the order in which those -callbacks are called is undefined. +. +This option (common for all limit types) specifies (if non-empty) a Tcl script +to be executed in the global namespace of the interpreter reading and writing +the option when the particular limit in the limited interpreter is exceeded. +The callback may modify the limit on the interpreter if it wishes the limited +interpreter to continue executing. If the callback generates an error, it is +reported through the background error mechanism (see \fBBACKGROUND ERROR +HANDLING\fR). Note that the callbacks defined by one interpreter are +completely isolated from the callbacks defined by another, and that the order +in which those callbacks are called is undefined. .TP \fB\-granularity\fR -This option (common for all limit types) specifies how frequently (out -of the points when the Tcl interpreter is in a consistent state where -limit checking is possible) that the limit is actually checked. This -allows the tuning of how frequently a limit is checked, and hence how -often the limit-checking overhead (which may be substantial in the -case of time limits) is incurred. +. +This option (common for all limit types) specifies how frequently (out of the +points when the Tcl interpreter is in a consistent state where limit checking +is possible) that the limit is actually checked. This allows the tuning of how +frequently a limit is checked, and hence how often the limit-checking overhead +(which may be substantial in the case of time limits) is incurred. .TP \fB\-milliseconds\fR -This option specifies the number of milliseconds after the moment -defined in the \fB\-seconds\fR option that the time limit will fire. -It should only ever be specified in conjunction with the -\fB\-seconds\fR option (whether it was set previously or is being set -this invocation.) +. +This option specifies the number of milliseconds after the moment defined in +the \fB\-seconds\fR option that the time limit will fire. It should only ever +be specified in conjunction with the \fB\-seconds\fR option (whether it was +set previously or is being set this invocation.) .TP \fB\-seconds\fR -This option specifies the number of seconds after the epoch (see -\fBclock seconds\fR) that the time limit for the interpreter will be -triggered. The limit will be triggered at the start of the second -unless specified at a sub-second level using the \fB\-milliseconds\fR -option. This option may be the empty string, which indicates that a -time limit is not set for the interpreter. +. +This option specifies the number of seconds after the epoch (see \fBclock +seconds\fR) that the time limit for the interpreter will be triggered. The +limit will be triggered at the start of the second unless specified at a +sub-second level using the \fB\-milliseconds\fR option. This option may be the +empty string, which indicates that a time limit is not set for the +interpreter. .TP \fB\-value\fR -This option specifies the number of commands that the interpreter may -execute before triggering the command limit. This option may be the -empty string, which indicates that a command limit is not set for the -interpreter. +. +This option specifies the number of commands that the interpreter may execute +before triggering the command limit. This option may be the empty string, +which indicates that a command limit is not set for the interpreter. .PP Where an interpreter with a resource limit set on it creates a slave -interpreter, that slave interpreter will have resource limits imposed -on it that are at least as restrictive as the limits on the creating -master interpreter. If the master interpreter of the limited master -wishes to relax these conditions, it should hide the \fBinterp\fR -command in the child and then use aliases and the \fBinterp -invokehidden\fR subcommand to provide such access as it chooses to the -\fBinterp\fR command to the limited master as necessary. -.VE 8.5 +interpreter, that slave interpreter will have resource limits imposed on it +that are at least as restrictive as the limits on the creating master +interpreter. If the master interpreter of the limited master wishes to relax +these conditions, it should hide the \fBinterp\fR command in the child and +then use aliases and the \fBinterp invokehidden\fR subcommand to provide such +access as it chooses to the \fBinterp\fR command to the limited master as +necessary. .SH "BACKGROUND ERROR HANDLING" -.VS 8.5 -When an error happens in a situation where it cannot be reported -directly up the stack (e.g. when processing events in an \fBupdate\fR -or \fBvwait\fR call) the error is instead reported through the -background error handling mechanism. Every interpreter has a -background error handler registered; the default error handler -arranges for the \fBbgerror\fR command in the interpreter's global -namespace to be called, but other error handlers may be installed and -process background errors in substantially different ways. -.PP -A background error handler consists of a non-empty list of words to -which will, at invocation time, be appended two further words. The -first word will be the error message string, and the second will a -dictionary of return options (this is also the sort of information -that can be obtained by trapping a normal error using \fBcatch\fR of -course.) The resulting list will then be executed in the interpreter's -global namespace without further substitutions being performed. +.PP +When an error happens in a situation where it cannot be reported directly up +the stack (e.g. when processing events in an \fBupdate\fR or \fBvwait\fR call) +the error is instead reported through the background error handling mechanism. +Every interpreter has a background error handler registered; the default error +handler arranges for the \fBbgerror\fR command in the interpreter's global +namespace to be called, but other error handlers may be installed and process +background errors in substantially different ways. +.PP +A background error handler consists of a non-empty list of words to which will +be appended two further words at invocation time. The first word will be the +error message string, and the second will a dictionary of return options (this +is also the sort of information that can be obtained by trapping a normal +error using \fBcatch\fR of course.) The resulting list will then be executed +in the interpreter's global namespace without further substitutions being +performed. .VE 8.5 .SH CREDITS This mechanism is based on the Safe-Tcl prototype implemented |