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Description of problem:
Using -re appears to lead to memory leaks in expect, its memory usage keeps going up indefinitely:

Example:
---------------------------------
#!/usr/bin/expect

spawn yes
log_user 0

while 1 {
   expect {
       -re ".+?\n" {
	   #
       }
   }
}
---------------------------------

Running script above for couple seconds leads to:
PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+ COMMAND
19334 root      20   0 1075m 606m  688 R 93.4 69.8   1:44.81 expect

Version-Release number of selected component (if applicable):
expect-5.44.1.15-4.el6.x86_64

How reproducible:
100%

Steps to Reproduce:
1. run attached reproducer

Actual results:
expect memory usage keeps going up

Expected results:
expect memory usage should be stable

Additional info:
Reported also here: http://sourceforge.net/p/expect/patches/13/

The patch from page linked in comment 0 makes the issue go away:

diff --git a/expect.c b/expect.c
index 65e6e04..185f9f3 100644
--- a/expect.c
+++ b/expect.c
@@ -185,9 +185,9 @@ free_ecase(
 {
     if (ec->i_list->duration == EXP_PERMANENT) {
        if (ec->pat)  { Tcl_DecrRefCount(ec->pat); }
-       if (ec->gate) { Tcl_DecrRefCount(ec->gate); }
        if (ec->body) { Tcl_DecrRefCount(ec->body); }
     }
+    if (ec->gate) { Tcl_DecrRefCount(ec->gate); }
 
     if (free_ilist) {
        ec->i_list->ecount--;

Used memory is holding stable at:
PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
31889 root      20   0  112m 2308 1796 R 94.5  0.3   1:43.09 expect

Thank you for bug report and investigation.