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Manual Pages for UNIX Operating System command usage for man Tcl_AddErrorInfo

Tcl Library Procedures Tcl_AddErrorInfo(3TCL)

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NAME

Tcl_AddObjErrorInfo, Tcl_AddErrorInfo, Tcl_SetObjErrorCode,

Tcl_SetErrorCode, Tcl_SetErrorCodeVA, Tcl_PosixError,

Tcl_LogCommandInfo - record information about errors

SYNOPSIS

#include

Tcl_AddObjErrorInfo(interp, message, length)

Tcl_AddErrorInfo(interp, message)

Tcl_SetObjErrorCode(interp, errorObjPtr)

Tcl_SetErrorCode(interp, element, element, ... (char *) NULL)

Tcl_SetErrorCodeVA(interp, argList)

CONST char *

Tcl_PosixError(interp)

void

Tcl_LogCommandInfo(interp, script, command, commandLength)

ARGUMENTS

Tcl_Interp *interp (in) Interpreter in which to

record information.

char *message (in) For Tcl_AddObjErrorInfo,

this points to the first byte of an array of bytes containing a string to record in the errorInfo variable. This byte array may contain embedded null bytes unless length is negative. For

Tcl_AddErrorInfo, this is

a conventional C string to record in the errorInfo variable. int length (in) The number of bytes to copy from message when setting the errorInfo variable. If negative, all bytes up to the first null byte are used.

Tcl_Obj *errorObjPtr(in) This variable errorCode

Tcl Last change: 8.0 1

Tcl Library Procedures Tcl_AddErrorInfo(3TCL)

will be set to this value. char *element (in) String to record as one

element of errorCode vari-

able. Last element argu-

ment must be NULL.

va_list argList (in) An argument list which

must have been initialized

using TCL_VARARGS_START,

and cleared using va_end.

CONST char *script (in) Pointer to first character

in script containing com-

mand (must be <= command) CONST char *command (in) Pointer to first character in command that generated the error

int commandLength(in) Number of bytes in com-

mand; -1 means use all

bytes up to first null byte

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DESCRIPTION

These procedures are used to manipulate two Tcl global vari-

ables that hold information about errors. The variable errorInfo holds a stack trace of the operations that were in progress when an error occurred, and is intended to be

human-readable. The variable errorCode holds a list of

items that are intended to be machine-readable. The first

item in errorCode identifies the class of error that

occurred (e.g. POSIX means an error occurred in a POSIX sys-

tem call) and additional elements in errorCode hold addi-

tional pieces of information that depend on the class. See the Tcl overview manual entry for details on the various formats for errorCode. The errorInfo variable is gradually built up as an error unwinds through the nested operations. Each time an error

code is returned to Tcl_EvalObjEx (or Tcl_Eval, which calls

Tcl_EvalObjEx) it calls the procedure Tcl_AddObjErrorInfo to

add additional text to errorInfo 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. Tcl Last change: 8.0 2

Tcl Library Procedures Tcl_AddErrorInfo(3TCL)

It is sometimes useful to add additional information to errorInfo beyond what can be supplied automatically by

Tcl_EvalObjEx. Tcl_AddObjErrorInfo may be used for this

purpose: its message and length arguments describe an addi-

tional string to be appended to errorInfo. For example, the

source command calls Tcl_AddObjErrorInfo to record the name

of the file being processed and the line number on which the error occurred; for Tcl procedures, the procedure name and line number within the procedure are recorded, and so on.

The best time to call Tcl_AddObjErrorInfo is just after

Tcl_EvalObjEx has returned TCL_ERROR. In calling

Tcl_AddObjErrorInfo, you may find it useful to use the

errorLine field of the interpreter (see the Tcl_Interp

manual entry for details).

Tcl_AddErrorInfo resembles Tcl_AddObjErrorInfo but differs

in initializing errorInfo from the string value of the interpreter's result if the error is just starting to be logged. It does not use the result as a Tcl object so any

embedded null characters in the result will cause informa-

tion to be lost. It also takes a conventional C string in

message instead of Tcl_AddObjErrorInfo's counted string.

The procedure Tcl_SetObjErrorCode is used to set the error-

Code variable. errorObjPtr contains a list object built up by the caller. errorCode is set to this value.

Tcl_SetObjErrorCode is typically invoked just before return-

ing an error in an object command. If an error is returned

without calling Tcl_SetObjErrorCode or Tcl_SetErrorCode the

Tcl interpreter automatically sets errorCode to NONE.

The procedure Tcl_SetErrorCode is also used to set the

errorCode variable. However, it takes one or more strings to record instead of an object. Otherwise, it is similar to

Tcl_SetObjErrorCode in behavior.

Tcl_SetErrorCodeVA is the same as Tcl_SetErrorCode except

that instead of taking a variable number of arguments it takes an argument list.

Tcl_PosixError sets the errorCode variable after an error in

a POSIX kernel call. It reads the value of the errno C

variable and calls Tcl_SetErrorCode to set errorCode in the

POSIX format. The caller must previously have called

Tcl_SetErrno to set errno; this is necessary on some plat-

forms (e.g. Windows) where Tcl is linked into an application

as a shared library, or when the error occurs in a dynami-

cally loaded extension. See the manual entry for

Tcl_SetErrno for more information.

Tcl_PosixError returns a human-readable diagnostic message

for the error (this is the same value that will appear as Tcl Last change: 8.0 3

Tcl Library Procedures Tcl_AddErrorInfo(3TCL)

the third element in errorCode). It may be convenient to include this string as part of the error message returned to the application in the interpreter's result.

Tcl_LogCommandInfo 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 errorInfo variable, and the line number stored internally in the

interpreter is set. On the first call to Tcl_LogCommandInfo

or Tcl_AddObjErrorInfo since an error occurred, the old

information in errorInfo is deleted. It is important to call the procedures described here rather than setting errorInfo or errorCode directly with

Tcl_ObjSetVar2. The reason for this is that the Tcl inter-

preter keeps information about whether these procedures have been called. For example, the first time

Tcl_AddObjErrorInfo is called for an error, it clears the

existing value of errorInfo and adds the error message in the interpreter's result to the variable before appending

message; in subsequent calls, it just appends the new mes-

sage. When Tcl_SetErrorCode is called, it sets a flag indi-

cating that errorCode has been set; this allows the Tcl interpreter to set errorCode to NONE if it receives an error

return when Tcl_SetErrorCode hasn't been called.

If the procedure Tcl_ResetResult is called, it clears all of

the state associated with errorInfo and errorCode (but it doesn't actually modify the variables). If an error had occurred, this will clear the error state to make it appear as if no error had occurred after all.

ATTRIBUTES

See attributes(5) for descriptions of the following attri-

butes: Tcl Last change: 8.0 4

Tcl Library Procedures Tcl_AddErrorInfo(3TCL)

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| ATTRIBUTE TYPE | ATTRIBUTE VALUE|

|____________________|__________________|_

| Availability | runtime/tcl-8 |

|____________________|__________________|_

| Interface Stability| Uncommitted |

|____________________|_________________|

NOTES Source for Tcl is available on http://opensolaris.org. Tcl Last change: 8.0 5

Manual Pages for UNIX Operating System command usage for man Tcl_AddErrorInfo

Tcl Library Procedures Tcl_AddErrorInfo(3TCL)

NAME

Tcl_AddObjErrorInfo, Tcl_AddErrorInfo, Tcl_SetObjErrorCode,

SYNOPSIS

Tcl_AddErrorInfo(interp, message)

Tcl_AddErrorInfo, this is

Tcl Library Procedures Tcl_AddErrorInfo(3TCL)

DESCRIPTION

Tcl Library Procedures Tcl_AddErrorInfo(3TCL)

Tcl_EvalObjEx has returned TCL_ERROR. In calling

Tcl_AddErrorInfo resembles Tcl_AddObjErrorInfo but differs

Tcl Library Procedures Tcl_AddErrorInfo(3TCL)

SEE ALSO

ATTRIBUTES

Tcl Library Procedures Tcl_AddErrorInfo(3TCL)

| ATTRIBUTE TYPE | ATTRIBUTE VALUE|