Tcl Library Procedures Tcl_SetResult(3TCL)
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NAME
Tcl_SetObjResult, Tcl_GetObjResult, Tcl_SetResult,
Tcl_GetStringResult, Tcl_AppendResult, Tcl_AppendResultVA,
Tcl_AppendElement, Tcl_ResetResult, Tcl_FreeResult - manipu-
late Tcl resultSYNOPSIS
#include
Tcl_SetObjResult(interp, objPtr)
Tcl_Obj *
Tcl_GetObjResult(interp)
Tcl_SetResult(interp, string, freeProc)
CONST char *Tcl_GetStringResult(interp)
Tcl_AppendResult(interp, string, string, ... , (char *) NULL)
Tcl_AppendResultVA(interp, argList)
Tcl_AppendElement(interp, string)
Tcl_ResetResult(interp)
Tcl_FreeResult(interp)
ARGUMENTSTcl_Interp *interp (out) Interpreter whose result
is to be modified or read.Tcl_Obj *objPtr (in) Object value to become
result for interp. char *string (in) String value to become result for interp or to be appended to the existing result.Tcl_FreeProc *freeProc (in) Address of procedure to
call to release storage at string, orTCL_STATIC, TCL_DYNAMIC,
or TCL_VOLATILE.
va_list argList (in) An argument list which
must have been Tcl Last change: 8.0 1Tcl Library Procedures Tcl_SetResult(3TCL)
initialised usingTCL_VARARGS_START, and
cleared using va_end.
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DESCRIPTION
The procedures described here are utilities for manipulating the result value in a Tcl interpreter. The interpreter result may be either a Tcl object or a string. For example,Tcl_SetObjResult and Tcl_SetResult set the interpreter
result to, respectively, an object and a string. Similarly,Tcl_GetObjResult and Tcl_GetStringResult return the inter-
preter result as an object and as a string. The procedures always keep the string and object forms of the interpreterresult consistent. For example, if Tcl_SetObjResult is
called to set the result to an object, thenTcl_GetStringResult is called, it will return the object's
string value.Tcl_SetObjResult arranges for objPtr to be the result for
interp, replacing any existing result. The result is left pointing to the object referenced by objPtr. objPtr's reference count is incremented since there is now a new reference to it from interp. The reference count for any old result object is decremented and the old result object is freed if no references to it remain.Tcl_GetObjResult returns the result for interp as an object.
The object's reference count is not incremented; if thecaller needs to retain a long-term pointer to the object
they should use Tcl_IncrRefCount to increment its reference
count in order to keep it from being freed too early or accidently changed.Tcl_SetResult arranges for string to be the result for the
current Tcl command in interp, replacing any existing result. The freeProc argument specifies how to manage thestorage for the string argument; it is discussed in the sec-
tion THE TCL_FREEPROC ARGUMENT TO TCL_SETRESULT below. If
string is NULL, then freeProc is ignored and Tcl_SetResult
re-initializes interp's result to point to an empty string.
Tcl_GetStringResult returns the result for interp as an
string. If the result was set to an object by aTcl_SetObjResult call, the object form will be converted to
a string and returned. If the object's string representa-
tion contains null bytes, this conversion will lose informa-
tion. For this reason, programmers are encouraged to write their code to use the new object API procedures and to callTcl_GetObjResult instead.
Tcl Last change: 8.0 2Tcl Library Procedures Tcl_SetResult(3TCL)
Tcl_ResetResult clears the result for interp and leaves the
result in its normal empty initialized state. If the result is an object, its reference count is decremented and the result is left pointing to an unshared object representing an empty string. If the result is a dynamically allocated string, its memory is free*d and the result is left as aempty string. Tcl_ResetResult also clears the error state
managed by Tcl_AddErrorInfo, Tcl_AddObjErrorInfo, and
Tcl_SetErrorCode.
OLD STRING PROCEDURES Use of the following procedures is deprecated since they manipulate the Tcl result as a string. Procedures such asTcl_SetObjResult that manipulate the result as an object can
be significantly more efficient.Tcl_AppendResult makes it easy to build up Tcl results in
pieces. It takes each of its string arguments and appends them in order to the current result associated with interp.If the result is in its initialized empty state (e.g. a com-
mand procedure was just invoked or Tcl_ResetResult was just
called), then Tcl_AppendResult sets the result to the con-
catenation of its string arguments. Tcl_AppendResult may be
called repeatedly as additional pieces of the result areproduced. Tcl_AppendResult takes care of all the storage
management issues associated with managing interp's result, such as allocating a larger result area if necessary. It also converts the current interpreter result from an object to a string, if necessary, before appending the argument strings. Any number of string arguments may be passed in a single call; the last argument in the list must be a NULL pointer.Tcl_AppendResultVA is the same as Tcl_AppendResult except
that instead of taking a variable number of arguments it takes an argument list.Tcl_AppendElement is similar to Tcl_AppendResult in that it
allows results to be built up in pieces. However,Tcl_AppendElement takes only a single string argument and it
appends that argument to the current result as a proper Tcllist element. Tcl_AppendElement adds backslashes or braces
if necessary to ensure that interp's result can be parsed asa list and that string will be extracted as a single ele-
ment. Under normal conditions, Tcl_AppendElement will add a
space character to interp's result just before adding the new list element, so that the list elements in the result are properly separated. However if the new list element isthe first in a list or sub-list (i.e. interp's current
result is empty, or consists of the single character ``{'', or ends in the characters `` {'') then no space is added. Tcl Last change: 8.0 3Tcl Library Procedures Tcl_SetResult(3TCL)
Tcl_FreeResult performs part of the work of Tcl_ResetResult.
It frees up the memory associated with interp's result. Italso sets interp->freeProc to zero, but doesn't change
interp->result or clear error state. Tcl_FreeResult is most
commonly used when a procedure is about to replace one result value with another.DIRECT ACCESS TO INTERP->RESULT IS DEPRECATED
It used to be legal for programs to directly read and writeinterp->result to manipulate the interpreter result. Direct
access to interp->result is now strongly deprecated because
it can make the result's string and object forms incon-
sistent. Programs should always read the result using theprocedures Tcl_GetObjResult or Tcl_GetStringResult, and
write the result using Tcl_SetObjResult or Tcl_SetResult.
THE TCL_FREEPROC ARGUMENT TO TCL_SETRESULT
Tcl_SetResult's freeProc argument specifies how the Tcl sys-
tem is to manage the storage for the string argument. IfTcl_SetResult or Tcl_SetObjResult are called at a time when
interp holds a string result, they do whatever is necessaryto dispose of the old string result (see the Tcl_Interp
manual entry for details on this).If freeProc is TCL_STATIC it means that string refers to an
area of static storage that is guaranteed not to be modifieduntil at least the next call to Tcl_Eval. If freeProc is
TCL_DYNAMIC it means that string was allocated with a call
to Tcl_Alloc and is now the property of the Tcl system.
Tcl_SetResult will arrange for the string's storage to be
released by calling Tcl_Free when it is no longer needed.
If freeProc is TCL_VOLATILE it means that string points to
an area of memory that is likely to be overwritten whenTcl_SetResult returns (e.g. it points to something in a
stack frame). In this case Tcl_SetResult will make a copy
of the string in dynamically allocated storage and arrange for the copy to be the result for the current Tcl command.If freeProc isn't one of the values TCL_STATIC, TCL_DYNAMIC,
and TCL_VOLATILE, then it is the address of a procedure that
Tcl should call to free the string. This allows applica-
tions to use non-standard storage allocators. When Tcl no
longer needs the storage for the string, it will call freeProc. FreeProc should have arguments and result thatmatch the type Tcl_FreeProc:
typedef void Tcl_FreeProc(char *blockPtr);
When freeProc is called, its blockPtr will be set to thevalue of string passed to Tcl_SetResult.
Tcl Last change: 8.0 4Tcl Library Procedures Tcl_SetResult(3TCL)
SEE ALSO
Tcl_AddErrorInfo, Tcl_CreateObjCommand, Tcl_SetErrorCode,
Tcl_Interp
KEYWORDS append, command, element, list, object, result, return value, interpreterATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:_______________________________________
| 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