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| 9 | '\" |
| 10 | '\" The definitions below are for supplemental macros used in Tcl/Tk |
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| 73 | '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. |
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| 208 | .SH "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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| 245 | .. |
| 246 | .TH Tcl_AddErrorInfo 3 8.0 Tcl "Tcl Library Procedures" |
| 247 | .BS |
| 248 | .SH NAME |
| 249 | Tcl_AddObjErrorInfo, Tcl_AddErrorInfo, Tcl_SetObjErrorCode, Tcl_SetErrorCode, Tcl_SetErrorCodeVA, Tcl_PosixError, Tcl_LogCommandInfo \- record information about errors |
| 250 | .SH SYNOPSIS |
| 251 | .nf |
| 252 | \fB#include <tcl.h>\fR |
| 253 | .sp |
| 254 | \fBTcl_AddObjErrorInfo\fR(\fIinterp, message, length\fR) |
| 255 | .sp |
| 256 | \fBTcl_AddErrorInfo\fR(\fIinterp, message\fR) |
| 257 | .sp |
| 258 | \fBTcl_SetObjErrorCode\fR(\fIinterp, errorObjPtr\fR) |
| 259 | .sp |
| 260 | \fBTcl_SetErrorCode\fR(\fIinterp, element, element, ... \fB(char *) NULL\fR) |
| 261 | .sp |
| 262 | \fBTcl_SetErrorCodeVA\fR(\fIinterp, argList\fR) |
| 263 | .sp |
| 264 | CONST char * |
| 265 | \fBTcl_PosixError\fR(\fIinterp\fR) |
| 266 | .sp |
| 267 | void |
| 268 | \fBTcl_LogCommandInfo\fR(\fIinterp, script, command, commandLength\fR) |
| 269 | .SH ARGUMENTS |
| 270 | .AS Tcl_Interp *message |
| 271 | .AP Tcl_Interp *interp in |
| 272 | Interpreter in which to record information. |
| 273 | .AP char *message in |
| 274 | For \fBTcl_AddObjErrorInfo\fR, |
| 275 | this points to the first byte of an array of bytes |
| 276 | containing a string to record in the \fBerrorInfo\fR variable. |
| 277 | This byte array may contain embedded null bytes |
| 278 | unless \fIlength\fR is negative. |
| 279 | For \fBTcl_AddErrorInfo\fR, |
| 280 | this is a conventional C string to record in the \fBerrorInfo\fR variable. |
| 281 | .AP int length in |
| 282 | The number of bytes to copy from \fImessage\fR when |
| 283 | setting the \fBerrorInfo\fR variable. |
| 284 | If negative, all bytes up to the first null byte are used. |
| 285 | .AP Tcl_Obj *errorObjPtr in |
| 286 | This variable \fBerrorCode\fR will be set to this value. |
| 287 | .AP char *element in |
| 288 | String to record as one element of \fBerrorCode\fR variable. |
| 289 | Last \fIelement\fR argument must be NULL. |
| 290 | .AP va_list argList in |
| 291 | An argument list which must have been initialized using |
| 292 | \fBTCL_VARARGS_START\fR, and cleared using \fBva_end\fR. |
| 293 | .AP "CONST char" *script in |
| 294 | Pointer to first character in script containing command (must be <= command) |
| 295 | .AP "CONST char" *command in |
| 296 | Pointer to first character in command that generated the error |
| 297 | .AP int commandLength in |
| 298 | Number of bytes in command; -1 means use all bytes up to first null byte |
| 299 | .BE |
| 300 | |
| 301 | .SH DESCRIPTION |
| 302 | .PP |
| 303 | These procedures are used to manipulate two Tcl global variables |
| 304 | that hold information about errors. |
| 305 | The variable \fBerrorInfo\fR holds a stack trace of the |
| 306 | operations that were in progress when an error occurred, |
| 307 | and is intended to be human-readable. |
| 308 | The variable \fBerrorCode\fR holds a list of items that |
| 309 | are intended to be machine-readable. |
| 310 | The first item in \fBerrorCode\fR identifies the class of |
| 311 | error that occurred |
| 312 | (e.g. POSIX means an error occurred in a POSIX system call) |
| 313 | and additional elements in \fBerrorCode\fR hold additional pieces |
| 314 | of information that depend on the class. |
| 315 | See the Tcl overview manual entry for details on the various |
| 316 | formats for \fBerrorCode\fR. |
| 317 | .PP |
| 318 | The \fBerrorInfo\fR variable is gradually built up as an |
| 319 | error unwinds through the nested operations. |
| 320 | Each time an error code is returned to \fBTcl_EvalObjEx\fR |
| 321 | (or \fBTcl_Eval\fR, which calls \fBTcl_EvalObjEx\fR) |
| 322 | it calls the procedure \fBTcl_AddObjErrorInfo\fR to add |
| 323 | additional text to \fBerrorInfo\fR describing the |
| 324 | command that was being executed when the error occurred. |
| 325 | By the time the error has been passed all the way back |
| 326 | to the application, it will contain a complete trace |
| 327 | of the activity in progress when the error occurred. |
| 328 | .PP |
| 329 | It is sometimes useful to add additional information to |
| 330 | \fBerrorInfo\fR beyond what can be supplied automatically |
| 331 | by \fBTcl_EvalObjEx\fR. |
| 332 | \fBTcl_AddObjErrorInfo\fR may be used for this purpose: |
| 333 | its \fImessage\fR and \fIlength\fR arguments describe an additional |
| 334 | string to be appended to \fBerrorInfo\fR. |
| 335 | For example, the \fBsource\fR command calls \fBTcl_AddObjErrorInfo\fR |
| 336 | to record the name of the file being processed and the |
| 337 | line number on which the error occurred; |
| 338 | for Tcl procedures, the procedure name and line number |
| 339 | within the procedure are recorded, and so on. |
| 340 | The best time to call \fBTcl_AddObjErrorInfo\fR is just after |
| 341 | \fBTcl_EvalObjEx\fR has returned \fBTCL_ERROR\fR. |
| 342 | In calling \fBTcl_AddObjErrorInfo\fR, you may find it useful to |
| 343 | use the \fBerrorLine\fR field of the interpreter (see the |
| 344 | \fBTcl_Interp\fR manual entry for details). |
| 345 | .PP |
| 346 | \fBTcl_AddErrorInfo\fR resembles \fBTcl_AddObjErrorInfo\fR |
| 347 | but differs in initializing \fBerrorInfo\fR from the string |
| 348 | value of the interpreter's result |
| 349 | if the error is just starting to be logged. |
| 350 | It does not use the result as a Tcl object |
| 351 | so any embedded null characters in the result |
| 352 | will cause information to be lost. |
| 353 | It also takes a conventional C string in \fImessage\fR |
| 354 | instead of \fBTcl_AddObjErrorInfo\fR's counted string. |
| 355 | .PP |
| 356 | The procedure \fBTcl_SetObjErrorCode\fR is used to set the |
| 357 | \fBerrorCode\fR variable. \fIerrorObjPtr\fR contains a list object |
| 358 | built up by the caller. \fBerrorCode\fR is set to this |
| 359 | value. \fBTcl_SetObjErrorCode\fR is typically invoked just |
| 360 | before returning an error in an object command. If an error is |
| 361 | returned without calling \fBTcl_SetObjErrorCode\fR or |
| 362 | \fBTcl_SetErrorCode\fR the Tcl interpreter automatically sets |
| 363 | \fBerrorCode\fR to \fBNONE\fR. |
| 364 | .PP |
| 365 | The procedure \fBTcl_SetErrorCode\fR is also used to set the |
| 366 | \fBerrorCode\fR variable. However, it takes one or more strings to |
| 367 | record instead of an object. Otherwise, it is similar to |
| 368 | \fBTcl_SetObjErrorCode\fR in behavior. |
| 369 | .PP |
| 370 | \fBTcl_SetErrorCodeVA\fR is the same as \fBTcl_SetErrorCode\fR except that |
| 371 | instead of taking a variable number of arguments it takes an argument list. |
| 372 | .PP |
| 373 | \fBTcl_PosixError\fR |
| 374 | sets the \fBerrorCode\fR variable after an error in a POSIX kernel call. |
| 375 | It reads the value of the \fBerrno\fR C variable and calls |
| 376 | \fBTcl_SetErrorCode\fR to set \fBerrorCode\fR in the \fBPOSIX\fR format. |
| 377 | The caller must previously have called \fBTcl_SetErrno\fR to set |
| 378 | \fBerrno\fR; this is necessary on some platforms (e.g. Windows) where Tcl |
| 379 | is linked into an application as a shared library, or when the error |
| 380 | occurs in a dynamically loaded extension. See the manual entry for |
| 381 | \fBTcl_SetErrno\fR for more information. |
| 382 | .PP |
| 383 | \fBTcl_PosixError\fR returns a human-readable diagnostic message |
| 384 | for the error |
| 385 | (this is the same value that will appear as the third element |
| 386 | in \fBerrorCode\fR). |
| 387 | It may be convenient to include this string as part of the |
| 388 | error message returned to the application in |
| 389 | the interpreter's result. |
| 390 | .PP |
| 391 | \fBTcl_LogCommandInfo\fR is invoked after an error occurs in an |
| 392 | interpreter. It adds information about the command that was being |
| 393 | executed when the error occurred to the \fBerrorInfo\fR variable, and |
| 394 | the line number stored internally in the interpreter is set. On the |
| 395 | first call to \fBTcl_LogCommandInfo\fR or \fBTcl_AddObjErrorInfo\fR |
| 396 | since an error occurred, the old information in \fBerrorInfo\fR is |
| 397 | deleted. |
| 398 | .PP |
| 399 | It is important to call the procedures described here rather than |
| 400 | setting \fBerrorInfo\fR or \fBerrorCode\fR directly with |
| 401 | \fBTcl_ObjSetVar2\fR. |
| 402 | The reason for this is that the Tcl interpreter keeps information |
| 403 | about whether these procedures have been called. |
| 404 | For example, the first time \fBTcl_AddObjErrorInfo\fR is called |
| 405 | for an error, it clears the existing value of \fBerrorInfo\fR |
| 406 | and adds the error message in the interpreter's result to the variable |
| 407 | before appending \fImessage\fR; |
| 408 | in subsequent calls, it just appends the new \fImessage\fR. |
| 409 | When \fBTcl_SetErrorCode\fR is called, it sets a flag indicating |
| 410 | that \fBerrorCode\fR has been set; |
| 411 | this allows the Tcl interpreter to set \fBerrorCode\fR to \fBNONE\fR |
| 412 | if it receives an error return |
| 413 | when \fBTcl_SetErrorCode\fR hasn't been called. |
| 414 | .PP |
| 415 | If the procedure \fBTcl_ResetResult\fR is called, |
| 416 | it clears all of the state associated with |
| 417 | \fBerrorInfo\fR and \fBerrorCode\fR |
| 418 | (but it doesn't actually modify the variables). |
| 419 | If an error had occurred, this will clear the error state to |
| 420 | make it appear as if no error had occurred after all. |
| 421 | |
| 422 | .SH "SEE ALSO" |
| 423 | Tcl_DecrRefCount, Tcl_IncrRefCount, Tcl_Interp, Tcl_ResetResult, Tcl_SetErrno |
| 424 | |
| 425 | .SH KEYWORDS |
| 426 | error, object, object result, stack, trace, variable |