Port Bug Report: psql can't work correctly

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POSTGRESQL BUG REPORT TEMPLATE
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Your name : Zhuo Gong
Your email address : gongzhuo(at)163(dot)net

Category : runtime: front-end
Severity : non-critical

Summary: psql can't work correctly

System Configuration
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Operating System : AIX4.1.5.0

PostgreSQL version : 6.4.2

Compiler used : gcc 2.8.1

Hardware:
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mvme 2600

Versions of other tools:
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gmake 3.77
flex 2.5.4
Bison A2.6

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Problem Description:
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When PostgreSQL is compiled with -O option , there is a bug in psql.
When command \dT or \df is used, the psql will exit .

All the situation just as this:
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$ psql
Welcome to the POSTGRESQL interactive sql monitor:
Please read the file COPYRIGHT for copyright terms of POSTGRESQL

type \? for help on slash commands
type \q to quit
type \g or terminate with semicolon to execute query
You are currently connected to the database: postgres

postgres=> \dt
Couldn't find any tables!
postgres=> \dT
pqReadData() -- backend closed the channel unexpectedly.
This probably means the backend terminated abnormally before or while pr
ocessing the request.
We have lost the connection to the backend, so further processing is impossible.
Terminating.
$

$ psql
Welcome to the POSTGRESQL interactive sql monitor:
Please read the file COPYRIGHT for copyright terms of POSTGRESQL

type \? for help on slash commands
type \q to quit
type \g or terminate with semicolon to execute query
You are currently connected to the database: postgres

postgres=> \df
pqReadData() -- backend closed the channel unexpectedly.
This probably means the backend terminated abnormally before or while pr
ocessing the request.
We have lost the connection to the backend, so further processing is impossible.
Terminating.
$
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When it is compiled with -g option , no problem of psql has
been found .

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Test Case:
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Solution:
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