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.)


client/mysqltest.c:
  Add "let" to the list of mysqltest commands that evaluates its arguments (only
  the right-hand-side of the equals-sign expression).
mysql-test/r/mysqltest.result:
  Added test to show that mysqltest "let" will evaluate the RHS correctly (and 
  expand the backslash test).
mysql-test/t/mysqltest.test:
  Added test to show that mysqltest "let" will evaluate the RHS correctly (and 
  expand the backslash test).
sql/mysql_priv.h:
  Increase the amount we require to be available for the stack, since 
  experience told us that the previous amount was too little by at least
  1044 bytes.
mysql-test/r/execution_constants.result:
  New BitKeeper file ``mysql-test/r/execution_constants.result''
mysql-test/t/execution_constants.test:
  New BitKeeper file ``mysql-test/t/execution_constants.test''

1 files changed, 12 insertions, 1 deletions

diff --git a/sql/mysql_priv.h b/sql/mysql_priv.h
index f293c769d75..5bf37d6b5f7 100644
--- a/sql/mysql_priv.h
+++ b/sql/mysql_priv.h
@@ -131,7 +131,18 @@ MY_LOCALE *my_locale_by_name(const char *name);
 #define MAX_ACCEPT_RETRY	10	// Test accept this many times
 #define MAX_FIELDS_BEFORE_HASH	32
 #define USER_VARS_HASH_SIZE     16
-#define STACK_MIN_SIZE		8192	// Abort if less stack during eval.
+
+/* 
+ Value of 9236 discovered through binary search 2006-09-26 on Ubuntu Dapper
+ Drake, libc6 2.3.6-0ubuntu2, Linux kernel 2.6.15-27-686, on x86.  (Added 
+ 100 bytes as reasonable buffer against growth and other environments'
+ requirements.)
+
+ Feel free to raise this by the smallest amount you can to get the
+ "execution_constants" test to pass.
+ */
+#define STACK_MIN_SIZE		9336	// Abort if less stack during eval.  
+
 #define STACK_MIN_SIZE_FOR_OPEN 1024*80
 #define STACK_BUFF_ALLOC	256	// For stack overrun checks
 #ifndef MYSQLD_NET_RETRY_COUNT