[Tcl-bugs] [ tcl-Bugs-2874678 ] dict incr leaks

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Bugs item #2874678, was opened at 2009-10-08 14:35
Message generated for change (Comment added) made by wastl-nagel
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Category: 15. Dict Object
Group: current: 8.5.7
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Sebastian Nagel (wastl-nagel)
Assigned to: Donal K. Fellows (dkf)
Summary: dict incr leaks

Initial Comment:
If a dict is created and filled via "dict incr" with a bigger set of keys it seems to leak. If the dict is destroyed (unset or overwritten) a lot of memory still keeps allocated. 

The following code consumes approx. 500MB memory on my machine (Linux, 64-bit):

set chars {a b c d e f g h i j k l m n o p q r s t u v w x y z
	A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
	0 1 2 3 4 5 6 7 8 9}

for {set i 0} {$i < 1000} {incr i} {
	append prefix [lindex $chars [expr int([tcl::mathfunc::rand]*62)]]
	set dictionary [dict create]
	foreach char $chars {
		foreach c $chars {
			dict incr dictionary $prefix$char$c $i
		}
	}
}

I've tested Tcl 8.5.2 (OpenSuSE 11.0, x86_64), 8.5.7, 8.6b1 (both built from source), 
all three leak, cf. attached valgrind log files for same code but only 100 cycles.

For 8.5.2 TclBN_mp_init_size according to valgrind seems to be reason.

% uname -mrvs
Linux 2.6.25.20-0.5-default #1 SMP 2009-08-14 01:48:11 +0200 x86_64

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>Comment By: Sebastian Nagel (wastl-nagel)
Date: 2009-10-08 15:26

Message:
May the patch below fix the problem?

--- ./generic/tclDictObj.c~     2009-01-06 17:07:17.000000000 +0100
+++ ./generic/tclDictObj.c      2009-10-08 15:00:29.000000000 +0200
@@ -2148,6 +2148,7 @@
            mp_int increment;

            code = Tcl_GetBignumFromObj(interp, objv[3], &increment);
+            mp_clear(&increment);
            if (code != TCL_OK) {
                Tcl_AddErrorInfo(interp, "\n    (reading increment)");
            } else {


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