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2 | '\" Copyright (c) 1989-1993 The Regents of the University of California. | |
3 | '\" Copyright (c) 1994-1996 Sun Microsystems, Inc. | |
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5 | '\" See the file "license.terms" for information on usage and redistribution | |
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8 | '\" RCS: @(#) $Id: CrtInterp.3,v 1.7 2002/06/26 11:50:52 msofer Exp $ | |
9 | '\" | |
10 | '\" The definitions below are for supplemental macros used in Tcl/Tk | |
11 | '\" manual entries. | |
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71 | '\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $ | |
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73 | '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. | |
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107 | .. | |
108 | .AS Tcl_Interp Tcl_CreateInterp in/out | |
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206 | '\" # SO - start of list of standard options | |
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208 | .SH "STANDARD OPTIONS" | |
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214 | '\" # SE - end of list of standard options | |
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219 | See the \\fBoptions\\fR manual entry for details on the standard options. | |
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226 | Command-Line Name: \\fB\\$1\\fR | |
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244 | \\$1\l'|0\(ul'\\$2 | |
245 | .. | |
246 | .TH Tcl_CreateInterp 3 7.5 Tcl "Tcl Library Procedures" | |
247 | .BS | |
248 | .SH NAME | |
249 | Tcl_CreateInterp, Tcl_DeleteInterp, Tcl_InterpDeleted \- create and delete Tcl command interpreters | |
250 | .SH SYNOPSIS | |
251 | .nf | |
252 | \fB#include <tcl.h>\fR | |
253 | .sp | |
254 | Tcl_Interp * | |
255 | \fBTcl_CreateInterp\fR() | |
256 | .sp | |
257 | \fBTcl_DeleteInterp\fR(\fIinterp\fR) | |
258 | .sp | |
259 | int | |
260 | \fBTcl_InterpDeleted\fR(\fIinterp\fR) | |
261 | .SH ARGUMENTS | |
262 | .AS Tcl_Interp *interp | |
263 | .AP Tcl_Interp *interp in | |
264 | Token for interpreter to be destroyed. | |
265 | .BE | |
266 | ||
267 | .SH DESCRIPTION | |
268 | .PP | |
269 | \fBTcl_CreateInterp\fR creates a new interpreter structure and returns | |
270 | a token for it. The token is required in calls to most other Tcl | |
271 | procedures, such as \fBTcl_CreateCommand\fR, \fBTcl_Eval\fR, and | |
272 | \fBTcl_DeleteInterp\fR. | |
273 | Clients are only allowed to access a few of the fields of | |
274 | Tcl_Interp structures; see the \fBTcl_Interp\fR | |
275 | and \fBTcl_CreateCommand\fR man pages for details. | |
276 | The new interpreter is initialized with the built-in Tcl commands | |
277 | and with the variables documented in tclvars(n). To bind in | |
278 | additional commands, call \fBTcl_CreateCommand\fR. | |
279 | .PP | |
280 | \fBTcl_DeleteInterp\fR marks an interpreter as deleted; the interpreter | |
281 | will eventually be deleted when all calls to \fBTcl_Preserve\fR for it have | |
282 | been matched by calls to \fBTcl_Release\fR. At that time, all of the | |
283 | resources associated with it, including variables, procedures, and | |
284 | application-specific command bindings, will be deleted. After | |
285 | \fBTcl_DeleteInterp\fR returns any attempt to use \fBTcl_Eval\fR on the | |
286 | interpreter will fail and return \fBTCL_ERROR\fR. After the call to | |
287 | \fBTcl_DeleteInterp\fR it is safe to examine the interpreter's result, | |
288 | query or set the values of variables, define, undefine or retrieve | |
289 | procedures, and examine the runtime evaluation stack. See below, in the | |
290 | section \fBINTERPRETERS AND MEMORY MANAGEMENT\fR for details. | |
291 | .PP | |
292 | \fBTcl_InterpDeleted\fR returns nonzero if \fBTcl_DeleteInterp\fR was | |
293 | called with \fIinterp\fR as its argument; this indicates that the | |
294 | interpreter will eventually be deleted, when the last call to | |
295 | \fBTcl_Preserve\fR for it is matched by a call to \fBTcl_Release\fR. If | |
296 | nonzero is returned, further calls to \fBTcl_Eval\fR in this interpreter | |
297 | will return \fBTCL_ERROR\fR. | |
298 | .PP | |
299 | \fBTcl_InterpDeleted\fR is useful in deletion callbacks to distinguish | |
300 | between when only the memory the callback is responsible for is being | |
301 | deleted and when the whole interpreter is being deleted. In the former case | |
302 | the callback may recreate the data being deleted, but this would lead to an | |
303 | infinite loop if the interpreter were being deleted. | |
304 | ||
305 | .SH "INTERPRETERS AND MEMORY MANAGEMENT" | |
306 | .PP | |
307 | \fBTcl_DeleteInterp\fR can be called at any time on an interpreter that may | |
308 | be used by nested evaluations and C code in various extensions. Tcl | |
309 | implements a simple mechanism that allows callers to use interpreters | |
310 | without worrying about the interpreter being deleted in a nested call, and | |
311 | without requiring special code to protect the interpreter, in most cases. | |
312 | This mechanism ensures that nested uses of an interpreter can safely | |
313 | continue using it even after \fBTcl_DeleteInterp\fR is called. | |
314 | .PP | |
315 | The mechanism relies on matching up calls to \fBTcl_Preserve\fR with calls | |
316 | to \fBTcl_Release\fR. If \fBTcl_DeleteInterp\fR has been called, only when | |
317 | the last call to \fBTcl_Preserve\fR is matched by a call to | |
318 | \fBTcl_Release\fR, will the interpreter be freed. See the manual entry for | |
319 | \fBTcl_Preserve\fR for a description of these functions. | |
320 | .PP | |
321 | The rules for when the user of an interpreter must call \fBTcl_Preserve\fR | |
322 | and \fBTcl_Release\fR are simple: | |
323 | .TP | |
324 | Interpreters Passed As Arguments | |
325 | Functions that are passed an interpreter as an argument can safely use the | |
326 | interpreter without any special protection. Thus, when you write an | |
327 | extension consisting of new Tcl commands, no special code is needed to | |
328 | protect interpreters received as arguments. This covers the majority of all | |
329 | uses. | |
330 | .TP | |
331 | Interpreter Creation And Deletion | |
332 | When a new interpreter is created and used in a call to \fBTcl_Eval\fR, | |
333 | \fBTcl_VarEval\fR, \fBTcl_GlobalEval\fR, \fBTcl_SetVar\fR, or | |
334 | \fBTcl_GetVar\fR, a pair of calls to \fBTcl_Preserve\fR and | |
335 | \fBTcl_Release\fR should be wrapped around all uses of the interpreter. | |
336 | Remember that it is unsafe to use the interpreter once \fBTcl_Release\fR | |
337 | has been called. To ensure that the interpreter is properly deleted when | |
338 | it is no longer needed, call \fBTcl_InterpDeleted\fR to test if some other | |
339 | code already called \fBTcl_DeleteInterp\fR; if not, call | |
340 | \fBTcl_DeleteInterp\fR before calling \fBTcl_Release\fR in your own code. | |
341 | .TP | |
342 | Retrieving An Interpreter From A Data Structure | |
343 | When an interpreter is retrieved from a data structure (e.g. the client | |
344 | data of a callback) for use in \fBTcl_Eval\fR, \fBTcl_VarEval\fR, | |
345 | \fBTcl_GlobalEval\fR, \fBTcl_SetVar\fR, or \fBTcl_GetVar\fR, a pair of | |
346 | calls to \fBTcl_Preserve\fR and \fBTcl_Release\fR should be wrapped around | |
347 | all uses of the interpreter; it is unsafe to reuse the interpreter once | |
348 | \fBTcl_Release\fR has been called. If an interpreter is stored inside a | |
349 | callback data structure, an appropriate deletion cleanup mechanism should | |
350 | be set up by the code that creates the data structure so that the | |
351 | interpreter is removed from the data structure (e.g. by setting the field | |
352 | to NULL) when the interpreter is deleted. Otherwise, you may be using an | |
353 | interpreter that has been freed and whose memory may already have been | |
354 | reused. | |
355 | .PP | |
356 | All uses of interpreters in Tcl and Tk have already been protected. | |
357 | Extension writers should ensure that their code also properly protects any | |
358 | additional interpreters used, as described above. | |
359 | ||
360 | .SH "SEE ALSO" | |
361 | Tcl_Preserve(3), Tcl_Release(3) | |
362 | ||
363 | .SH KEYWORDS | |
364 | command, create, delete, interpreter |