Re: [HACKERS] Win32 WEXITSTATUS too - Mailing list pgsql-patches

From: "Bruce Momjian" <bruce@momjian.us>
 Yes, you are 100% correct that I had exceptions and errors confused.
I
> have backed out the patch that used FormatMessage(), and instead of
> using a URL, the message is now:
>
> child process was terminated by exception %X
> See /include/ntstatus.h for a description of the hex value.
>
> When I search for /include/ntstatus.h, I get the Wine page first, so
> hopefully we can mark this item as completed.

Thank you, Bruce-san.  I agree.


----- Original Message -----
From: "Bruce Momjian" <bruce@momjian.us>
To: "Takayuki Tsunakawa" <tsunakawa.takay@jp.fujitsu.com>
Cc: "PostgreSQL-patches" <pgsql-patches@postgresql.org>; "Tom Lane"
<tgl@sss.pgh.pa.us>; "Alvaro Herrera" <alvherre@commandprompt.com>;
"Magnus Hagander" <magnus@hagander.net>; "ITAGAKI Takahiro"
<itagaki.takahiro@oss.ntt.co.jp>
Sent: Tuesday, January 23, 2007 12:35 PM
Subject: Re: [pgsql-patches] [HACKERS] Win32 WEXITSTATUS too


> Takayuki Tsunakawa wrote:
>> From: "Bruce Momjian" <bruce@momjian.us>
>> > OK, I have tested on MinGW and found I can use FormatMessage() to
>> print
>> > a description for all ERROR* system() failures, rather than print
a
>> hex
>> > value.  This removes the need for a URL or lookup of hex values.
>> > Attached and applied.
>>
>> Excuse me if I'm misunderstanding, but I'm afraid you are mixing up
>> Win32 error codes and exception codes.  I saw the following
fragment
>> in your patch:
>>
>> !  * On MinGW, system() returns STATUS_* values.  MSVC might be
>> !  * different.  To test, create a binary that does *(NULL), and
>> !  * then create a second binary that calls it via system(),
>> !  * and check the return value of system().  On MinGW, it is
>> !  * 0xC0000005 == STATUS_ACCESS_VIOLATION, and 0x5 is a value
>> !  * FormatMessage() can look up.  GetLastError() does not work;
>> !  * always zero.
>>
>> Exception codes and error codes are different and not related.  In
the
>> above test, 0xC0000005 is an "exception code". On the other hand,
what
>> FormatMessage() accepts is an error code.  Error codes can't
derived
>> from exception codes.  Stripping off 0xC bit from an exception code
>> does not convert it to an error code.
>> I suspect the reason why you misunderstood is that the descriptions
>> are similar:
>> the description for exception 0xC0000005 (STATUS_ACCESS_VIOLATION)
is
>> "access violation" (though the text can't be obtained).  This is
>> caused by an illegal memory access.  This is a program bug.
>> The description for 0x5 (ERROR_ACCESS_DENIED) is "Access is
denied."
>> This is caused by permission checks.  This is not a bug, and can
>> happen normally.
>>
>> Try "1.0 / 0.0" (devide by zero) instead of (*NULL).  What would
your
>> patch display?  The exception would be 0xC000008E
>> (STATUS_FLOAT_DIVIDE_BY_ZERO), I think.  0x8E is ERROR_BUSY_DRIVE.
>
> Yes, you are 100% correct that I had exceptions and errors confused.
I
> have backed out the patch that used FormatMessage(), and instead of
> using a URL, the message is now:
>
> child process was terminated by exception %X
> See /include/ntstatus.h for a description of the hex value.
>
> When I search for /include/ntstatus.h, I get the Wine page first, so
> hopefully we can mark this item as completed.
>
> --
>  Bruce Momjian   bruce@momjian.us
>  EnterpriseDB    http://www.enterprisedb.com
>
>  + If your life is a hard drive, Christ can be your backup. +
>
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