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Overview
Comment:Make defaults work even when [upvar]ed to just a non-existent element.
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Timelines: family | ancestors | descendants | both | tip-508
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SHA3-256: 6faaafb4019cf50b9fd541a0741c826e2f0eca9b7f08f67ba24667c04da2479b
User & Date: dkf 2018-09-26 13:08:46
Context
2018-09-26
13:09
Improved comment. Closed-Leaf check-in: f0dd67ee95 user: dkf tags: tip-508
13:08
Make defaults work even when [upvar]ed to just a non-existent element. check-in: 6faaafb401 user: dkf tags: tip-508
09:47
merge core-8-branch check-in: 4c46bf91dd user: dkf tags: tip-508
Changes
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Changes to generic/tclInt.h.

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			    Tcl_Obj **errorObjPtr);

/*
 * TIP #508: [array default]
 */

MODULE_SCOPE void	TclInitArrayVar(Var *arrayPtr);


/*
 * Utility routines for encoding index values as integers. Used by both
 * some of the command compilers and by [lsort] and [lsearch].
 */

MODULE_SCOPE int	TclIndexEncode(Tcl_Interp *interp, Tcl_Obj *objPtr,






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			    Tcl_Obj **errorObjPtr);

/*
 * TIP #508: [array default]
 */

MODULE_SCOPE void	TclInitArrayVar(Var *arrayPtr);
MODULE_SCOPE Tcl_Obj *	TclGetArrayDefault(Var *arrayPtr);

/*
 * Utility routines for encoding index values as integers. Used by both
 * some of the command compilers and by [lsort] and [lsearch].
 */

MODULE_SCOPE int	TclIndexEncode(Tcl_Interp *interp, Tcl_Obj *objPtr,

Changes to generic/tclVar.c.

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				 * Tcl_NextHashEntry to get value to
				 * return. */
    struct ArraySearch *nextPtr;/* Next in list of all active searches for
				 * this variable, or NULL if this is the last
				 * one. */
} ArraySearch;













/*
 * Forward references to functions defined later in this file:
 */

static void		AppendLocals(Tcl_Interp *interp, Tcl_Obj *listPtr,
			    Tcl_Obj *patternPtr, int includeLinks);
static void		ArrayPopulateSearch(Tcl_Interp *interp,
................................................................................
 * TIP #508: [array default]
 */

static int		ArrayDefaultCmd(ClientData clientData,
			    Tcl_Interp *interp, int objc,
			    Tcl_Obj *const objv[]);
static void		DeleteArrayVar(Var *arrayPtr);
static Tcl_Obj *	GetArrayDefault(Var *arrayPtr);
static void		SetArrayDefault(Var *arrayPtr, Tcl_Obj *defaultObj);

/*
 * Functions defined in this file that may be exported in the future for use
 * by the bytecode compiler and engine or to the public interface.
 */

................................................................................
    if (TclIsVarScalar(varPtr) && !TclIsVarUndefined(varPtr)) {
	return varPtr->value.objPtr;
    }

    /*
     * Return the array default value if any.
     */

    if (arrayPtr && TclIsVarArray(arrayPtr) && GetArrayDefault(arrayPtr)) {
	return GetArrayDefault(arrayPtr);












    }

    if (flags & TCL_LEAVE_ERR_MSG) {
	if (TclIsVarUndefined(varPtr) && arrayPtr
		&& !TclIsVarUndefined(arrayPtr)) {
	    msg = noSuchElement;
	} else if (TclIsVarArray(varPtr)) {
................................................................................
    if (oldValuePtr == NULL) {
	/*
	 * No previous value. Check for defaults if there's an array we can
	 * ask this of.
	 */

	if (arrayPtr) {
	    Tcl_Obj *defValuePtr = GetArrayDefault(arrayPtr);

	    if (defValuePtr) {
		oldValuePtr = Tcl_DuplicateObj(defValuePtr);
	    }
	}

	if (oldValuePtr == NULL) {
................................................................................
     * If there was no previous value, either we use the array's default (if
     * this is an array with a default at all) or we treat this as a simple
     * set.
     */

    if (oldValuePtr == NULL) {
	if (arrayPtr) {
	    Tcl_Obj *defValuePtr = GetArrayDefault(arrayPtr);

	    if (defValuePtr) {
		/*
		 * This is *almost* the same as the shared path below, except
		 * that the original value reference in defValuePtr is not
		 * decremented.
		 */
................................................................................
    /*
     * Only compare string representations of the same length.
     */

    return ((l1 == l2) && !memcmp(p1, p2, l1));
}
 
/*
 * TIP #508: [array default]
 */

/*
 * The following structure extends the regular TclVarHashTable used by array
 * variables to store their optional default value.
 */

typedef struct ArrayVarHashTable {
    TclVarHashTable table;
    Tcl_Obj *defaultObj;
} ArrayVarHashTable;
 
/*----------------------------------------------------------------------
 *
 * ArrayDefaultCmd --
 *
 *	This function implements the 'array default' Tcl command. 
 *	Refer to the user documentation for details on what it does.
 *
 * Results:
 *	Returns a standard Tcl result.
 *
 * Side effects:
 *	See the user documentation.
................................................................................
	    Tcl_WrongNumArgs(interp, 2, objv, "arrayName");
	    return TCL_ERROR;
	}
	if (!varPtr || TclIsVarUndefined(varPtr) || !isArray) {
	    return NotArrayError(interp, arrayNameObj);
	}

	defaultValueObj = GetArrayDefault(varPtr);
	if (!defaultValueObj) {
	    /* Array default must exist. */
	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
		    "array has no default value", -1));
	    Tcl_SetErrorCode(interp, "TCL", "READ", "ARRAY", "DEFAULT", NULL);
	    return TCL_ERROR;
	}
................................................................................
	    return TCL_ERROR;
	}

	/*
	 * Attempt to create array if needed.
	 */
	varPtr = TclObjLookupVarEx(interp, arrayNameObj, NULL,
		/*flags*/ TCL_LEAVE_ERR_MSG, /*msg*/ "array default set", 
		/*createPart1*/ 1, /*createPart2*/ 1, &arrayPtr);
	if (varPtr == NULL) {
	    return TCL_ERROR;
	}
	if (arrayPtr) {
	    /*
	     * Not a valid array name.
	     */
	    
	    CleanupVar(varPtr, arrayPtr);
	    TclObjVarErrMsg(interp, arrayNameObj, NULL, "array default set",
		    needArray, -1);
	    Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "VARNAME",
		    TclGetString(arrayNameObj), NULL);
	    return TCL_ERROR;
	}
................................................................................
	 */

	if (!varPtr || TclIsVarUndefined(varPtr)) {
	    Tcl_SetObjResult(interp, Tcl_NewBooleanObj(0));
	} else if (!isArray) {
	    return NotArrayError(interp, arrayNameObj);
	} else {
	    defaultValueObj = GetArrayDefault(varPtr);
	    Tcl_SetObjResult(interp, Tcl_NewBooleanObj(!!defaultValueObj));
	}
	return TCL_OK;

    case OPT_UNSET:
	if (objc != 3) {
	    Tcl_WrongNumArgs(interp, 2, objv, "arrayName");
................................................................................
 * Initialize array variable.
 */

void
TclInitArrayVar(
    Var *arrayPtr)
{
    ArrayVarHashTable *tablePtr;





    TclSetVarArray(arrayPtr);

    tablePtr = ckalloc(sizeof(ArrayVarHashTable));




    // Regular TclVarHashTable initialization.
    arrayPtr->value.tablePtr = (TclVarHashTable *) tablePtr;
    TclInitVarHashTable(arrayPtr->value.tablePtr, TclGetVarNsPtr(arrayPtr));


    // Default value initialization.


    tablePtr->defaultObj = NULL;
}
 
/*
 * Cleanup array variable.
 */

static void
DeleteArrayVar(
    Var *arrayPtr)
{
    ArrayVarHashTable *tablePtr = (ArrayVarHashTable *) arrayPtr->value.tablePtr;



    // Default value cleanup.


    SetArrayDefault(arrayPtr, NULL);


    // Regular TclVarHashTable cleanup.
    VarHashDeleteTable(arrayPtr->value.tablePtr);



    ckfree(tablePtr);
}
 
/*
 * Get array default value if any.
 */

static Tcl_Obj *
GetArrayDefault(
    Var *arrayPtr)
{
    ArrayVarHashTable *tablePtr = (ArrayVarHashTable *) arrayPtr->value.tablePtr;


    return tablePtr->defaultObj;
}
 
/*
 * Set/replace/unset array default value.
 */

static void
SetArrayDefault(
    Var *arrayPtr,
    Tcl_Obj *defaultObj)
{
    ArrayVarHashTable *tablePtr = (ArrayVarHashTable *) arrayPtr->value.tablePtr;

    
    /*
     * Increment/decrement refcount twice to ensure that the object is shared,
     * so that it doesn't get modified accidentally by the folling code:
     * 
     *      array default set v 1
     *      lappend v(a) 2; # returns a new object {1 2}
     *      set v(b); # returns the original default object "1"
     */

    if (tablePtr->defaultObj) {
        Tcl_DecrRefCount(tablePtr->defaultObj);
        Tcl_DecrRefCount(tablePtr->defaultObj);
    }
    tablePtr->defaultObj = defaultObj;
    if (tablePtr->defaultObj) {
        Tcl_IncrRefCount(tablePtr->defaultObj);






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				 * Tcl_NextHashEntry to get value to
				 * return. */
    struct ArraySearch *nextPtr;/* Next in list of all active searches for
				 * this variable, or NULL if this is the last
				 * one. */
} ArraySearch;

/*
 * TIP #508: [array default]
 *
 * The following structure extends the regular TclVarHashTable used by array
 * variables to store their optional default value.
 */

typedef struct ArrayVarHashTable {
    TclVarHashTable table;
    Tcl_Obj *defaultObj;
} ArrayVarHashTable;

/*
 * Forward references to functions defined later in this file:
 */

static void		AppendLocals(Tcl_Interp *interp, Tcl_Obj *listPtr,
			    Tcl_Obj *patternPtr, int includeLinks);
static void		ArrayPopulateSearch(Tcl_Interp *interp,
................................................................................
 * TIP #508: [array default]
 */

static int		ArrayDefaultCmd(ClientData clientData,
			    Tcl_Interp *interp, int objc,
			    Tcl_Obj *const objv[]);
static void		DeleteArrayVar(Var *arrayPtr);

static void		SetArrayDefault(Var *arrayPtr, Tcl_Obj *defaultObj);

/*
 * Functions defined in this file that may be exported in the future for use
 * by the bytecode compiler and engine or to the public interface.
 */

................................................................................
    if (TclIsVarScalar(varPtr) && !TclIsVarUndefined(varPtr)) {
	return varPtr->value.objPtr;
    }

    /*
     * Return the array default value if any.
     */

    if (arrayPtr && TclIsVarArray(arrayPtr) && TclGetArrayDefault(arrayPtr)) {
	return TclGetArrayDefault(arrayPtr);
    }
    if (TclIsVarArrayElement(varPtr) && !arrayPtr) {
	/*
	 * UGLY! Peek inside the implementation of things.
	 */

	ArrayVarHashTable *avhtPtr = (ArrayVarHashTable *)
		((VarInHash *) varPtr)->entry.tablePtr;

	if (avhtPtr->defaultObj) {
	    return avhtPtr->defaultObj;
	}
    }

    if (flags & TCL_LEAVE_ERR_MSG) {
	if (TclIsVarUndefined(varPtr) && arrayPtr
		&& !TclIsVarUndefined(arrayPtr)) {
	    msg = noSuchElement;
	} else if (TclIsVarArray(varPtr)) {
................................................................................
    if (oldValuePtr == NULL) {
	/*
	 * No previous value. Check for defaults if there's an array we can
	 * ask this of.
	 */

	if (arrayPtr) {
	    Tcl_Obj *defValuePtr = TclGetArrayDefault(arrayPtr);

	    if (defValuePtr) {
		oldValuePtr = Tcl_DuplicateObj(defValuePtr);
	    }
	}

	if (oldValuePtr == NULL) {
................................................................................
     * If there was no previous value, either we use the array's default (if
     * this is an array with a default at all) or we treat this as a simple
     * set.
     */

    if (oldValuePtr == NULL) {
	if (arrayPtr) {
	    Tcl_Obj *defValuePtr = TclGetArrayDefault(arrayPtr);

	    if (defValuePtr) {
		/*
		 * This is *almost* the same as the shared path below, except
		 * that the original value reference in defValuePtr is not
		 * decremented.
		 */
................................................................................
    /*
     * Only compare string representations of the same length.
     */

    return ((l1 == l2) && !memcmp(p1, p2, l1));
}
 














/*----------------------------------------------------------------------
 *
 * ArrayDefaultCmd --
 *
 *	This function implements the 'array default' Tcl command.
 *	Refer to the user documentation for details on what it does.
 *
 * Results:
 *	Returns a standard Tcl result.
 *
 * Side effects:
 *	See the user documentation.
................................................................................
	    Tcl_WrongNumArgs(interp, 2, objv, "arrayName");
	    return TCL_ERROR;
	}
	if (!varPtr || TclIsVarUndefined(varPtr) || !isArray) {
	    return NotArrayError(interp, arrayNameObj);
	}

	defaultValueObj = TclGetArrayDefault(varPtr);
	if (!defaultValueObj) {
	    /* Array default must exist. */
	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
		    "array has no default value", -1));
	    Tcl_SetErrorCode(interp, "TCL", "READ", "ARRAY", "DEFAULT", NULL);
	    return TCL_ERROR;
	}
................................................................................
	    return TCL_ERROR;
	}

	/*
	 * Attempt to create array if needed.
	 */
	varPtr = TclObjLookupVarEx(interp, arrayNameObj, NULL,
		/*flags*/ TCL_LEAVE_ERR_MSG, /*msg*/ "array default set",
		/*createPart1*/ 1, /*createPart2*/ 1, &arrayPtr);
	if (varPtr == NULL) {
	    return TCL_ERROR;
	}
	if (arrayPtr) {
	    /*
	     * Not a valid array name.
	     */

	    CleanupVar(varPtr, arrayPtr);
	    TclObjVarErrMsg(interp, arrayNameObj, NULL, "array default set",
		    needArray, -1);
	    Tcl_SetErrorCode(interp, "TCL", "LOOKUP", "VARNAME",
		    TclGetString(arrayNameObj), NULL);
	    return TCL_ERROR;
	}
................................................................................
	 */

	if (!varPtr || TclIsVarUndefined(varPtr)) {
	    Tcl_SetObjResult(interp, Tcl_NewBooleanObj(0));
	} else if (!isArray) {
	    return NotArrayError(interp, arrayNameObj);
	} else {
	    defaultValueObj = TclGetArrayDefault(varPtr);
	    Tcl_SetObjResult(interp, Tcl_NewBooleanObj(!!defaultValueObj));
	}
	return TCL_OK;

    case OPT_UNSET:
	if (objc != 3) {
	    Tcl_WrongNumArgs(interp, 2, objv, "arrayName");
................................................................................
 * Initialize array variable.
 */

void
TclInitArrayVar(
    Var *arrayPtr)
{
    ArrayVarHashTable *tablePtr = ckalloc(sizeof(ArrayVarHashTable));

    /*
     * Mark the variable as an array.
     */

    TclSetVarArray(arrayPtr);


    /*
     * Regular TclVarHashTable initialization.
     */


    arrayPtr->value.tablePtr = (TclVarHashTable *) tablePtr;
    TclInitVarHashTable(arrayPtr->value.tablePtr, TclGetVarNsPtr(arrayPtr));

    /*
     * Default value initialization.
     */

    tablePtr->defaultObj = NULL;
}
 
/*
 * Cleanup array variable.
 */

static void
DeleteArrayVar(
    Var *arrayPtr)
{
    ArrayVarHashTable *tablePtr = (ArrayVarHashTable *)
	    arrayPtr->value.tablePtr;

    /*
     * Default value cleanup.
     */

    SetArrayDefault(arrayPtr, NULL);

    /*
     * Regular TclVarHashTable cleanup.

     */

    VarHashDeleteTable(arrayPtr->value.tablePtr);
    ckfree(tablePtr);
}
 
/*
 * Get array default value if any.
 */

Tcl_Obj *
TclGetArrayDefault(
    Var *arrayPtr)
{
    ArrayVarHashTable *tablePtr = (ArrayVarHashTable *)
	    arrayPtr->value.tablePtr;

    return tablePtr->defaultObj;
}
 
/*
 * Set/replace/unset array default value.
 */

static void
SetArrayDefault(
    Var *arrayPtr,
    Tcl_Obj *defaultObj)
{
    ArrayVarHashTable *tablePtr = (ArrayVarHashTable *)
	    arrayPtr->value.tablePtr;

    /*
     * Increment/decrement refcount twice to ensure that the object is shared,
     * so that it doesn't get modified accidentally by the folling code:
     *
     *      array default set v 1
     *      lappend v(a) 2; # returns a new object {1 2}
     *      set v(b); # returns the original default object "1"
     */

    if (tablePtr->defaultObj) {
        Tcl_DecrRefCount(tablePtr->defaultObj);
        Tcl_DecrRefCount(tablePtr->defaultObj);
    }
    tablePtr->defaultObj = defaultObj;
    if (tablePtr->defaultObj) {
        Tcl_IncrRefCount(tablePtr->defaultObj);

Changes to tests/set-old.test.

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    }
    foo
} {1 {"x" isn't an array}}
test set-old-8.6 {array command} {
    catch {unset a}
    set a(22) 3
    list [catch {array gorp a} msg] $msg
} {1 {unknown or ambiguous subcommand "gorp": must be anymore, donesearch, exists, for, get, names, nextelement, set, size, startsearch, statistics, or unset}}
test set-old-8.7 {array command, anymore option} {
    catch {unset a}
    list [catch {array anymore a x} msg] $msg
} {1 {"a" isn't an array}}
test set-old-8.8 {array command, anymore option, array doesn't exist yet but has compiler-allocated procedure slot} {
    proc foo {x} {
        if {$x==1} {
................................................................................
    }}} msg] $msg
} {1 {list must have an even number of elements}}

test set-old-9.1 {ids for array enumeration} {
    catch {unset a}
    set a(a) 1
    list [array star a] [array star a] [array done a s-1-a; array star a] \
	    [array done a s-2-a; array d a s-3-a; array start a]
} {s-1-a s-2-a s-3-a s-1-a}
test set-old-9.2 {array enumeration} {
    catch {unset a}
    set a(a) 1
    set a(b) 1
    set a(c) 1
    set x [array startsearch a]






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    }
    foo
} {1 {"x" isn't an array}}
test set-old-8.6 {array command} {
    catch {unset a}
    set a(22) 3
    list [catch {array gorp a} msg] $msg
} {1 {unknown or ambiguous subcommand "gorp": must be anymore, default, donesearch, exists, for, get, names, nextelement, set, size, startsearch, statistics, or unset}}
test set-old-8.7 {array command, anymore option} {
    catch {unset a}
    list [catch {array anymore a x} msg] $msg
} {1 {"a" isn't an array}}
test set-old-8.8 {array command, anymore option, array doesn't exist yet but has compiler-allocated procedure slot} {
    proc foo {x} {
        if {$x==1} {
................................................................................
    }}} msg] $msg
} {1 {list must have an even number of elements}}

test set-old-9.1 {ids for array enumeration} {
    catch {unset a}
    set a(a) 1
    list [array star a] [array star a] [array done a s-1-a; array star a] \
	    [array done a s-2-a; array do a s-3-a; array start a]
} {s-1-a s-2-a s-3-a s-1-a}
test set-old-9.2 {array enumeration} {
    catch {unset a}
    set a(a) 1
    set a(b) 1
    set a(c) 1
    set x [array startsearch a]