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authordkf <donal.k.fellows@manchester.ac.uk>2001-11-19 14:35:54 (GMT)
committerdkf <donal.k.fellows@manchester.ac.uk>2001-11-19 14:35:54 (GMT)
commitd74ef041362e5b4eeea97da995d6829f2a88b479 (patch)
tree44763cdd57d94ad774bd93b56a8d0d53c0287675 /doc
parentabe43ad4ad63a11db7f9841ed2a9f3991197231f (diff)
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Changes due to TIP#68; memory handling in variable traces is now correct!
Diffstat (limited to 'doc')
-rw-r--r--doc/TraceVar.348
1 files changed, 41 insertions, 7 deletions
diff --git a/doc/TraceVar.3 b/doc/TraceVar.3
index 226a460..b8c5efb 100644
--- a/doc/TraceVar.3
+++ b/doc/TraceVar.3
@@ -5,7 +5,7 @@
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
-'\" RCS: @(#) $Id: TraceVar.3,v 1.4 2000/04/14 23:01:54 hobbs Exp $
+'\" RCS: @(#) $Id: TraceVar.3,v 1.5 2001/11/19 14:35:54 dkf Exp $
'\"
.so man.macros
.TH Tcl_TraceVar 3 7.4 Tcl "Tcl Library Procedures"
@@ -43,8 +43,9 @@ If the name references an element of an array, then it
must be in writable memory: Tcl will make temporary modifications
to it while looking up the name.
.AP int flags in
-OR-ed combination of the values TCL_TRACE_READS, TCL_TRACE_WRITES, and
-TCL_TRACE_UNSETS, TCL_TRACE_ARRAY, and TCL_GLOBAL_ONLY.
+OR-ed combination of the values TCL_TRACE_READS, TCL_TRACE_WRITES,
+TCL_TRACE_UNSETS, TCL_TRACE_ARRAY, TCL_GLOBAL_ONLY, TCL_NAMESPACE_ONLY,
+TCL_TRACE_RESULT_DYNAMIC and TCL_TRACE_RESULT_OBJECT.
Not all flags are used by all
procedures. See below for more information.
.AP Tcl_VarTraceProc *proc in
@@ -84,6 +85,11 @@ Normally, the variable will be looked up at the current level of
procedure call; if this bit is set then the variable will be looked
up at global level, ignoring any active procedures.
.TP
+\fBTCL_NAMESPACE_ONLY\fR
+Normally, the variable will be looked up at the current level of
+procedure call; if this bit is set then the variable will be looked
+up in the current namespace, ignoring any active procedures.
+.TP
\fBTCL_TRACE_READS\fR
Invoke \fIproc\fR whenever an attempt is made to read the variable.
.TP
@@ -102,6 +108,21 @@ Invoke \fIproc\fR whenever the array command is invoked.
This gives the trace procedure a chance to update the array before
array names or array get is called. Note that this is called
before an array set, but that will trigger write traces.
+.VS 8.4
+.TP
+\fBTCL_TRACE_RESULT_DYNAMIC\fR
+The result of invoking the \fIproc\fR is a dynamically allocated
+string that will be released by the Tcl library via a call to
+\fBckfree\fR. Must not be specified at the same time as
+TCL_TRACE_RESULT_OBJECT.
+.TP
+\fBTCL_TRACE_RESULT_OBJECT\fR
+The result of invoking the \fIproc\fR is a Tcl_Obj* (cast to a char*)
+with a reference count of at least one. The ownership of that
+reference will be transferred to the Tcl core for release (when the
+core has finished with it) via a call to \fBTcl_DecrRefCount\fR. Must
+not be specified at the same time as TCL_TRACE_RESULT_DYNAMIC.
+.VE 8.4
.PP
Whenever one of the specified operations occurs on the variable,
\fIproc\fR will be invoked.
@@ -135,6 +156,11 @@ accessed is a global one not accessible from the current level of
procedure call: the trace procedure will need to pass this flag
back to variable-related procedures like \fBTcl_GetVar\fR if it
attempts to access the variable.
+The bit TCL_NAMESPACE_ONLY will be set whenever the variable being
+accessed is a namespace one not accessible from the current level of
+procedure call: the trace procedure will need to pass this flag
+back to variable-related procedures like \fBTcl_GetVar\fR if it
+attempts to access the variable.
The bit TCL_TRACE_DESTROYED will be set in \fIflags\fR if the trace is
about to be destroyed; this information may be useful to \fIproc\fR
so that it can clean up its own internal data structures (see
@@ -159,9 +185,10 @@ traces set on a given variable.
The return value from \fBTcl_VarTraceInfo\fR is the \fIclientData\fR
associated with a particular trace.
The trace must be on the variable specified by the \fIinterp\fR,
-\fIvarName\fR, and \fIflags\fR arguments (only the TCL_GLOBAL_ONLY
-bit from \fIflags\fR is used; other bits are ignored) and its trace procedure
-must the same as the \fIproc\fR argument.
+\fIvarName\fR, and \fIflags\fR arguments (only the TCL_GLOBAL_ONLY and
+TCL_NAMESPACE_ONLY bits from \fIflags\fR is used; other bits are
+ignored) and its trace procedure must the same as the \fIproc\fR
+argument.
If the \fIprevClientData\fR argument is NULL then the return
value corresponds to the first (most recently created) matching
trace, or NULL if there are no matching traces.
@@ -297,7 +324,14 @@ successful completion.
If \fIproc\fR returns a non-NULL value it signifies that an
error occurred.
The return value must be a pointer to a static character string
-containing an error message.
+containing an error message,
+.VS 8.4
+unless (\fIexactly\fR one of) the TCL_TRACE_RESULT_DYNAMIC and
+TCL_TRACE_RESULT_OBJECT flags is set, which specify that the result is
+either a dynamic string (to be released with \fBckfree\fR) or a
+Tcl_Obj* (cast to char* and to be released with
+\fBTcl_DecrRefCount\fR) containing the error message.
+.VE 8.4
If a trace procedure returns an error, no further traces are
invoked for the access and the traced access aborts with the
given message.