313 lines
14 KiB
Groff
313 lines
14 KiB
Groff
'\"
|
|
'\" Copyright (c) 1989-1993 The Regents of the University of California.
|
|
'\" Copyright (c) 1994-1997 Sun Microsystems, Inc.
|
|
'\"
|
|
'\" See the file "license.terms" for information on usage and redistribution
|
|
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
|
|
'\"
|
|
.TH Tcl_AddErrorInfo 3 8.5 Tcl "Tcl Library Procedures"
|
|
.so man.macros
|
|
.BS
|
|
.SH NAME
|
|
Tcl_GetReturnOptions, Tcl_SetReturnOptions, Tcl_AddErrorInfo, Tcl_AppendObjToErrorInfo, Tcl_AddObjErrorInfo, Tcl_SetObjErrorCode, Tcl_SetErrorCode, Tcl_SetErrorCodeVA, Tcl_SetErrorLine, Tcl_GetErrorLine, Tcl_PosixError, Tcl_LogCommandInfo \- retrieve or record information about errors and other return options
|
|
.SH SYNOPSIS
|
|
.nf
|
|
\fB#include <tcl.h>\fR
|
|
.sp
|
|
Tcl_Obj *
|
|
\fBTcl_GetReturnOptions\fR(\fIinterp, code\fR)
|
|
.sp
|
|
int
|
|
\fBTcl_SetReturnOptions\fR(\fIinterp, options\fR)
|
|
.sp
|
|
\fBTcl_AddErrorInfo\fR(\fIinterp, message\fR)
|
|
.sp
|
|
\fBTcl_AppendObjToErrorInfo\fR(\fIinterp, objPtr\fR)
|
|
.sp
|
|
\fBTcl_AddObjErrorInfo\fR(\fIinterp, message, length\fR)
|
|
.sp
|
|
\fBTcl_SetObjErrorCode\fR(\fIinterp, errorObjPtr\fR)
|
|
.sp
|
|
\fBTcl_SetErrorCode\fR(\fIinterp, element, element, ... \fB(char *) NULL\fR)
|
|
.sp
|
|
\fBTcl_SetErrorCodeVA\fR(\fIinterp, argList\fR)
|
|
.sp
|
|
\fBTcl_GetErrorLine\fR(\fIinterp\fR)
|
|
.sp
|
|
\fBTcl_SetErrorLine\fR(\fIinterp, lineNum\fR)
|
|
.sp
|
|
const char *
|
|
\fBTcl_PosixError\fR(\fIinterp\fR)
|
|
.sp
|
|
void
|
|
\fBTcl_LogCommandInfo\fR(\fIinterp, script, command, commandLength\fR)
|
|
.SH ARGUMENTS
|
|
.AS Tcl_Interp commandLength
|
|
.AP Tcl_Interp *interp in
|
|
Interpreter in which to record information.
|
|
.AP int code
|
|
The code returned from script evaluation.
|
|
.AP Tcl_Obj *options
|
|
A dictionary of return options.
|
|
.AP "const char" *message in
|
|
For \fBTcl_AddErrorInfo\fR,
|
|
this is a conventional C string to append to the \fB\-errorinfo\fR return option.
|
|
For \fBTcl_AddObjErrorInfo\fR,
|
|
this points to the first byte of an array of \fIlength\fR bytes
|
|
containing a string to append to the \fB\-errorinfo\fR return option.
|
|
This byte array may contain embedded null bytes
|
|
unless \fIlength\fR is negative.
|
|
.AP Tcl_Obj *objPtr in
|
|
A message to be appended to the \fB\-errorinfo\fR return option
|
|
in the form of a Tcl_Obj value.
|
|
.AP int length in
|
|
The number of bytes to copy from \fImessage\fR when
|
|
appending to the \fB\-errorinfo\fR return option.
|
|
If negative, all bytes up to the first null byte are used.
|
|
.AP Tcl_Obj *errorObjPtr in
|
|
The \fB\-errorcode\fR return option will be set to this value.
|
|
.AP "const char" *element in
|
|
String to record as one element of the \fB\-errorcode\fR return option.
|
|
Last \fIelement\fR argument must be NULL.
|
|
.AP va_list argList in
|
|
An argument list which must have been initialized using
|
|
\fBva_start\fR, and cleared using \fBva_end\fR.
|
|
.AP int lineNum
|
|
The line number of a script where an error occurred.
|
|
.AP "const char" *script in
|
|
Pointer to first character in script containing command (must be <= command)
|
|
.AP "const char" *command in
|
|
Pointer to first character in command that generated the error
|
|
.AP int commandLength in
|
|
Number of bytes in command; -1 means use all bytes up to first null byte
|
|
.BE
|
|
.SH DESCRIPTION
|
|
.PP
|
|
The \fBTcl_SetReturnOptions\fR and \fBTcl_GetReturnOptions\fR
|
|
routines expose the same capabilities as the \fBreturn\fR and
|
|
\fBcatch\fR commands, respectively, in the form of a C interface.
|
|
.PP
|
|
\fBTcl_GetReturnOptions\fR retrieves the dictionary of return options
|
|
from an interpreter following a script evaluation.
|
|
Routines such as \fBTcl_Eval\fR are called to evaluate a
|
|
script in an interpreter. These routines return an integer
|
|
completion code. These routines also leave in the interpreter
|
|
both a result and a dictionary of return options generated
|
|
by script evaluation. Just as \fBTcl_GetObjResult\fR retrieves
|
|
the result, \fBTcl_GetReturnOptions\fR retrieves the dictionary
|
|
of return options. The integer completion code should be
|
|
passed as the \fIcode\fR argument to \fBTcl_GetReturnOptions\fR
|
|
so that all required options will be present in the dictionary.
|
|
Specifically, a \fIcode\fR value of \fBTCL_ERROR\fR will
|
|
ensure that entries for the keys \fB\-errorinfo\fR,
|
|
\fB\-errorcode\fR, and \fB\-errorline\fR will appear in the
|
|
dictionary. Also, the entries for the keys \fB\-code\fR
|
|
and \fB\-level\fR will be adjusted if necessary to agree
|
|
with the value of \fIcode\fR. The \fB(Tcl_Obj *)\fR returned
|
|
by \fBTcl_GetReturnOptions\fR points to an unshared
|
|
\fBTcl_Obj\fR with reference count of zero. The dictionary
|
|
may be written to, either adding, removing, or overwriting
|
|
any entries in it, without the need to check for a shared value.
|
|
As with any \fBTcl_Obj\fR with reference count of zero, it is up to
|
|
the caller to arrange for its disposal with \fBTcl_DecrRefCount\fR or
|
|
to a reference to it via \fBTcl_IncrRefCount\fR (or one of the many
|
|
functions that call that, notably including \fBTcl_SetObjResult\fR and
|
|
\fBTcl_SetVar2Ex\fR).
|
|
.PP
|
|
A typical usage for \fBTcl_GetReturnOptions\fR is to
|
|
retrieve the stack trace when script evaluation returns
|
|
\fBTCL_ERROR\fR, like so:
|
|
.PP
|
|
.CS
|
|
int code = Tcl_Eval(interp, script);
|
|
if (code == TCL_ERROR) {
|
|
Tcl_Obj *options = \fBTcl_GetReturnOptions\fR(interp, code);
|
|
Tcl_Obj *key = Tcl_NewStringObj("-errorinfo", -1);
|
|
Tcl_Obj *stackTrace;
|
|
Tcl_IncrRefCount(key);
|
|
Tcl_DictObjGet(NULL, options, key, &stackTrace);
|
|
Tcl_DecrRefCount(key);
|
|
/* Do something with stackTrace */
|
|
Tcl_DecrRefCount(options);
|
|
}
|
|
.CE
|
|
.PP
|
|
\fBTcl_SetReturnOptions\fR sets the return options
|
|
of \fIinterp\fR to be \fIoptions\fR. If \fIoptions\fR
|
|
contains any invalid value for any key, TCL_ERROR will
|
|
be returned, and the interp result will be set to an
|
|
appropriate error message. Otherwise, a completion code
|
|
in agreement with the \fB\-code\fR and \fB\-level\fR
|
|
keys in \fIoptions\fR will be returned.
|
|
.PP
|
|
As an example, Tcl's \fBreturn\fR command itself could
|
|
be implemented in terms of \fBTcl_SetReturnOptions\fR
|
|
like so:
|
|
.PP
|
|
.CS
|
|
if ((objc % 2) == 0) { /* explicit result argument */
|
|
objc--;
|
|
Tcl_SetObjResult(interp, objv[objc]);
|
|
}
|
|
return \fBTcl_SetReturnOptions\fR(interp, Tcl_NewListObj(objc-1, objv+1));
|
|
.CE
|
|
.PP
|
|
(It is not really implemented that way. Internal access
|
|
privileges allow for a more efficient alternative that meshes
|
|
better with the bytecode compiler.)
|
|
.PP
|
|
Note that a newly created \fBTcl_Obj\fR may be passed
|
|
in as the \fIoptions\fR argument without the need to tend
|
|
to any reference counting. This is analogous to
|
|
\fBTcl_SetObjResult\fR.
|
|
.PP
|
|
While \fBTcl_SetReturnOptions\fR provides a general interface
|
|
to set any collection of return options, there are a handful
|
|
of return options that are very frequently used. Most
|
|
notably the \fB\-errorinfo\fR and \fB\-errorcode\fR return
|
|
options should be set properly when the command procedure
|
|
of a command returns \fBTCL_ERROR\fR. The \fB\-errorline\fR
|
|
return option is also read by commands that evaluate scripts
|
|
and wish to supply detailed error location information in
|
|
the stack trace text they append to the \fB\-errorinfo\fR option.
|
|
Tcl provides several simpler interfaces to more directly set
|
|
these return options.
|
|
.PP
|
|
The \fB\-errorinfo\fR option holds a stack trace of the
|
|
operations that were in progress when an error occurred,
|
|
and is intended to be human-readable.
|
|
The \fB\-errorcode\fR option holds a Tcl list of items that
|
|
are intended to be machine-readable.
|
|
The first item in the \fB\-errorcode\fR value identifies the class of
|
|
error that occurred
|
|
(e.g., POSIX means an error occurred in a POSIX system call)
|
|
and additional elements hold additional pieces
|
|
of information that depend on the class.
|
|
See the manual entry on the \fBerrorCode\fR variable for details on the
|
|
various formats for the \fB\-errorcode\fR option used by Tcl's built-in
|
|
commands.
|
|
.PP
|
|
The \fB\-errorinfo\fR option value is gradually built up as an
|
|
error unwinds through the nested operations.
|
|
Each time an error code is returned to \fBTcl_Eval\fR, or
|
|
any of the routines that performs script evaluation,
|
|
the procedure \fBTcl_AddErrorInfo\fR is called to add
|
|
additional text to the \fB\-errorinfo\fR value describing the
|
|
command that was being executed when the error occurred.
|
|
By the time the error has been passed all the way back
|
|
to the application, it will contain a complete trace
|
|
of the activity in progress when the error occurred.
|
|
.PP
|
|
It is sometimes useful to add additional information to
|
|
the \fB\-errorinfo\fR value beyond what can be supplied automatically
|
|
by the script evaluation routines.
|
|
\fBTcl_AddErrorInfo\fR may be used for this purpose:
|
|
its \fImessage\fR argument is an additional
|
|
string to be appended to the \fB\-errorinfo\fR option.
|
|
For example, when an error arises during the \fBsource\fR command,
|
|
the procedure \fBTcl_AddErrorInfo\fR is called to
|
|
record the name of the file being processed and the
|
|
line number on which the error occurred.
|
|
Likewise, when an error arises during evaluation of a
|
|
Tcl procedures, the procedure name and line number
|
|
within the procedure are recorded, and so on.
|
|
The best time to call \fBTcl_AddErrorInfo\fR is just after
|
|
a script evaluation routine has returned \fBTCL_ERROR\fR.
|
|
The value of the \fB\-errorline\fR return option (retrieved
|
|
via a call to \fBTcl_GetReturnOptions\fR) often makes up
|
|
a useful part of the \fImessage\fR passed to \fBTcl_AddErrorInfo\fR.
|
|
.PP
|
|
\fBTcl_AppendObjToErrorInfo\fR is an alternative interface to the
|
|
same functionality as \fBTcl_AddErrorInfo\fR. \fBTcl_AppendObjToErrorInfo\fR
|
|
is called when the string value to be appended to the \fB\-errorinfo\fR option
|
|
is available as a \fBTcl_Obj\fR instead of as a \fBchar\fR array.
|
|
.PP
|
|
\fBTcl_AddObjErrorInfo\fR is nearly identical
|
|
to \fBTcl_AddErrorInfo\fR, except that it has an additional \fIlength\fR
|
|
argument. This allows the \fImessage\fR string to contain
|
|
embedded null bytes. This is essentially never a good idea.
|
|
If the \fImessage\fR needs to contain the null character \fBU+0000\fR,
|
|
Tcl's usual internal encoding rules should be used to avoid
|
|
the need for a null byte. If the \fBTcl_AddObjErrorInfo\fR
|
|
interface is used at all, it should be with a negative \fIlength\fR value.
|
|
.PP
|
|
The procedure \fBTcl_SetObjErrorCode\fR is used to set the
|
|
\fB\-errorcode\fR return option to the list value \fIerrorObjPtr\fR
|
|
built up by the caller.
|
|
\fBTcl_SetObjErrorCode\fR is typically invoked just
|
|
before returning an error. If an error is
|
|
returned without calling \fBTcl_SetObjErrorCode\fR or
|
|
\fBTcl_SetErrorCode\fR the Tcl interpreter automatically sets
|
|
the \fB\-errorcode\fR return option to \fBNONE\fR.
|
|
.PP
|
|
The procedure \fBTcl_SetErrorCode\fR is also used to set the
|
|
\fB\-errorcode\fR return option. However, it takes one or more strings to
|
|
record instead of a value. Otherwise, it is similar to
|
|
\fBTcl_SetObjErrorCode\fR in behavior.
|
|
.PP
|
|
\fBTcl_SetErrorCodeVA\fR is the same as \fBTcl_SetErrorCode\fR except that
|
|
instead of taking a variable number of arguments it takes an argument list.
|
|
.PP
|
|
The procedure \fBTcl_GetErrorLine\fR is used to read the integer value
|
|
of the \fB\-errorline\fR return option without the overhead of a full
|
|
call to \fBTcl_GetReturnOptions\fR. Likewise, \fBTcl_SetErrorLine\fR
|
|
sets the \fB\-errorline\fR return option value.
|
|
.PP
|
|
\fBTcl_PosixError\fR
|
|
sets the \fB\-errorcode\fR variable after an error in a POSIX kernel call.
|
|
It reads the value of the \fBerrno\fR C variable and calls
|
|
\fBTcl_SetErrorCode\fR to set the \fB\-errorcode\fR return
|
|
option in the \fBPOSIX\fR format.
|
|
The caller must previously have called \fBTcl_SetErrno\fR to set
|
|
\fBerrno\fR; this is necessary on some platforms (e.g. Windows) where Tcl
|
|
is linked into an application as a shared library, or when the error
|
|
occurs in a dynamically loaded extension. See the manual entry for
|
|
\fBTcl_SetErrno\fR for more information.
|
|
.PP
|
|
\fBTcl_PosixError\fR returns a human-readable diagnostic message
|
|
for the error
|
|
(this is the same value that will appear as the third element
|
|
in the \fB\-errorcode\fR value).
|
|
It may be convenient to include this string as part of the
|
|
error message returned to the application in
|
|
the interpreter's result.
|
|
.PP
|
|
\fBTcl_LogCommandInfo\fR is invoked after an error occurs in an
|
|
interpreter. It adds information about the command that was being
|
|
executed when the error occurred to the \fB\-errorinfo\fR value, and
|
|
the line number stored internally in the interpreter is set.
|
|
.PP
|
|
In older releases of Tcl, there was no \fBTcl_GetReturnOptions\fR
|
|
routine. In its place, the global Tcl variables \fBerrorInfo\fR
|
|
and \fBerrorCode\fR were the only place to retrieve the error
|
|
information. Much existing code written for older Tcl releases
|
|
still access this information via those global variables.
|
|
.PP
|
|
It is important to realize that while reading from those
|
|
global variables remains a supported way to access these
|
|
return option values, it is important not to assume that
|
|
writing to those global variables will properly set the
|
|
corresponding return options. It has long been emphasized
|
|
in this manual page that it is important to
|
|
call the procedures described here rather than
|
|
setting \fBerrorInfo\fR or \fBerrorCode\fR directly with
|
|
\fBTcl_ObjSetVar2\fR.
|
|
.PP
|
|
If the procedure \fBTcl_ResetResult\fR is called,
|
|
it clears all of the state of the interpreter associated with
|
|
script evaluation, including the entire return options dictionary.
|
|
In particular, the \fB\-errorinfo\fR and \fB\-errorcode\fR options
|
|
are reset.
|
|
If an error had occurred, the \fBTcl_ResetResult\fR call will
|
|
clear the error state to make it appear as if no error had
|
|
occurred after all.
|
|
The global variables \fBerrorInfo\fR and
|
|
\fBerrorCode\fR are not modified by \fBTcl_ResetResult\fR
|
|
so they continue to hold a record of information about the
|
|
most recent error seen in an interpreter.
|
|
.SH "SEE ALSO"
|
|
Tcl_DecrRefCount(3), Tcl_IncrRefCount(3), Tcl_Interp(3), Tcl_ResetResult(3),
|
|
Tcl_SetErrno(3), errorCode(n), errorInfo(n)
|
|
.SH KEYWORDS
|
|
error, value, value result, stack, trace, variable
|