Bug#21476: (Thread stack overrun not caught, causing SEGV)

The STACK_MIN_SIZE is currently set to 8192, when we actually need 
(emperically discovered) 9236 bytes to raise an fatal error, on Ubuntu 
Dapper Drake, libc6 2.3.6-0ubuntu2, Linux kernel 2.6.15-27-686, on x86.

I'm taking that as a new lower bound, plus 100B of wiggle-room for sundry
word sizes and stack behaviors.

The added test verifies in a cross-platform way that there are no gaps 
between the space that we think we need and what we actually need to report 
an error.

DOCUMENTERS:  This also adds "let" to the mysqltest commands that evaluate
an argument to expand variables therein.  (Only right of the "=", of course.)

1 files changed, 9 insertions, 3 deletions

diff --git a/client/mysqltest.c b/client/mysqltest.c
index 0f0abe682b5..ca588b7ba24 100644
--- a/client/mysqltest.c
+++ b/client/mysqltest.c
@@ -1609,7 +1609,10 @@ int do_save_master_pos()
 int do_let(struct st_query *query)
 {
   char *p= query->first_argument;
-  char *var_name, *var_name_end, *var_val_start;
+  char *var_name, *var_name_end;
+  DYNAMIC_STRING let_rhs_expr;
+
+  init_dynamic_string(&let_rhs_expr, "", 512, 2048);
 
   /* Find <var_name> */
   if (!*p)
@@ -1628,10 +1631,13 @@ int do_let(struct st_query *query)
   /* Find start of <var_val> */
   while (*p && my_isspace(charset_info,*p))
     p++;
-  var_val_start= p;
+
+  do_eval(&let_rhs_expr, p, FALSE);
+
   query->last_argument= query->end;
   /* Assign var_val to var_name */
-  return var_set(var_name, var_name_end, var_val_start, query->end);
+  return var_set(var_name, var_name_end, let_rhs_expr.str, 
+                 (let_rhs_expr.str + let_rhs_expr.length));
 }