Tcl Source Code

point to constant strings or may be shared with other parts of the
interpreter.
Note also that the argument strings are encoded in normalized UTF-8 since
version 8.1 of Tcl.
.PP
\fIProc\fR must return an integer code that is expected to be one of
\fBTCL_OK\fR, \fBTCL_ERROR\fR, \fBTCL_RETURN\fR, \fBTCL_BREAK\fR, or
\fBTCL_CONTINUE\fR. See the \fBreturn\fR man page for details on
what these codes mean and the use of extended values for an extension's
private use. Most normal commands will only return \fBTCL_OK\fR
or \fBTCL_ERROR\fR.
.PP
In addition, \fIproc\fR must set
the interpreter result;
in the case of a \fBTCL_OK\fR return code this gives the result
of the command, and in the case of \fBTCL_ERROR\fR it gives an error message.
The \fBTcl_SetResult\fR procedure provides an easy interface for setting
the return value;  for complete details on how the interpreter result
field is managed, see the \fBTcl_Interp\fR man page.
Before invoking a command procedure,

\fBTcl_GetIntFromObj\fR on \fIobjv\fR[\fB2\fR] to obtain the integer
representation of that value; that call may change the type of the value
that \fIobjv\fR[\fB2\fR] points at, but will not change where
\fIobjv\fR[\fB2\fR] points.
.PP
\fIproc\fR must return an integer code that is either \fBTCL_OK\fR,
\fBTCL_ERROR\fR, \fBTCL_RETURN\fR, \fBTCL_BREAK\fR, or \fBTCL_CONTINUE\fR.

See the \fBreturn\fR man page for details on what these codes mean and the
use of extended values for an extension's private use. Most normal commands
will only return \fBTCL_OK\fR or \fBTCL_ERROR\fR.
.PP
In addition, if \fIproc\fR needs to return a non-empty result,
it can call \fBTcl_SetObjResult\fR to set the interpreter's result.
In the case of a \fBTCL_OK\fR return code this gives the result
of the command,
and in the case of \fBTCL_ERROR\fR this gives an error message.
Before invoking a command procedure,
\fBTcl_EvalObjEx\fR sets interpreter's result to

value corresponding to the exceptional return code returned by evaluation
of \fIscript\fR.  Tcl defines the normal return code from script
evaluation to be zero (0), or \fBTCL_OK\fR.  Tcl also defines four exceptional
return codes: 1 (\fBTCL_ERROR\fR), 2 (\fBTCL_RETURN\fR), 3 (\fBTCL_BREAK\fR),
and 4 (\fBTCL_CONTINUE\fR).  Errors during evaluation of a script are indicated
by a return code of \fBTCL_ERROR\fR.  The other exceptional return codes are
returned by the \fBreturn\fR, \fBbreak\fR, and \fBcontinue\fR commands
and in other special situations as documented.
New commands defined by Tcl packages as well as scripts that make
use of the \fBreturn \-code\fR  command can return other integer
values as the return code. These must however lie outside the range
reserved for Tcl as documented for the \fBreturn\fR command.

.PP
If the \fIresultVarName\fR argument is given, then the variable it names is
set to the result of the script evaluation.  When the return code from the
script is 1 (\fBTCL_ERROR\fR), the value stored in \fIresultVarName\fR is an
error message.  When the return code from the script is 0 (\fBTCL_OK\fR), the
value stored in \fIresultVarName\fR is the value returned from \fIscript\fR.
.PP

The return code of the procedure is 4 (\fBTCL_CONTINUE\fR).  The
procedure command behaves in its calling context as if it
were the command \fBcontinue\fR.
.TP 13
\fIvalue\fR
.
\fIValue\fR must be an integer;  it will be returned as the
return code for the current procedure. Applications
and packages should use values in the range 5 to 1073741823 (0x3fffffff)
for their own purposes. Values outside this range are reserved
for use by Tcl.
.LP
When a procedure wants to signal that it has received invalid
arguments from its caller, it may use \fBreturn -code error\fR
with \fIresult\fR set to a suitable error message.  Otherwise
usage of the \fBreturn -code\fR option is mostly limited to
procedures that implement a new control structure.
.PP

 * TCL_RETURN		The command requests that the current function return;
 *			the interpreter's result contains the function's
 *			return value.
 * TCL_BREAK		The command requests that the innermost loop be
 *			exited; the interpreter's result is meaningless.
 * TCL_CONTINUE		Go on to the next iteration of the current loop; the
 *			interpreter's result is meaningless.
 * Integer return codes in the range TCL_CODE_USER_MIN to TCL_CODE_USER_MAX are
 * reserved for the use of packages.
 */

#define TCL_OK			0
#define TCL_ERROR		1
#define TCL_RETURN		2
#define TCL_BREAK		3
#define TCL_CONTINUE		4
#define TCL_CODE_USER_MIN	5
#define TCL_CODE_USER_MAX	0x3fffffff /*  1073741823 */

/*
 *----------------------------------------------------------------------------
 * Flags to control what substitutions are performed by Tcl_SubstObj():
 */

#define TCL_SUBST_COMMANDS	001