Mailing-List:	contact cygwin-help AT sourceware DOT cygnus DOT com; run by ezmlm
List-Subscribe:	<mailto:cygwin-subscribe AT sources DOT redhat DOT com>
List-Archive:	<http://sources.redhat.com/ml/cygwin/>
List-Post:	<mailto:cygwin AT sources DOT redhat DOT com>
List-Help:	<mailto:cygwin-help AT sources DOT redhat DOT com>, <http://sources.redhat.com/ml/#faqs>
Sender:	cygwin-owner AT sources DOT redhat DOT com
Delivered-To:	mailing list cygwin AT sources DOT redhat DOT com
From:	steve DOT snyder AT philips DOT com
To:	<cygwin AT cygwin DOT com>
Subject:	Cygwin libs broken by "-fomit-frame-pointer" switch
Message-ID:	<0056910011738630000002L102*@MHS>
Date:	Mon, 30 Apr 2001 17:47:24 -0500
MIME-Version:	1.0
X-MIME-Autoconverted:	from quoted-printable to 8bit by delorie.com id SAA19384

Hello.

I have noticed that building the Cygwin libraries with the 
"-fomit-frame-pointer" compiler switch breaks the libraries.  No errors 
are seen in compiling/linking, but an attempt to use a program that relies 
on the library (bash, for instance) always causes a stack fault.  This is 
with v1.3.1-1 of the Cygwin code and v2.95.3-4 of the compiler.  

(Some background for those who don't know what I'm talking about: By 
default GCC dedicates one of the precious few x86 registers, EBP, as a 
base pointer for local variables.  However the stack pointer, ESP, can 
just as easily be used for this task, freeing EBP for other uses.  The 
"-fomit-frame-pointer" switch tells the compiler to do just that.) 

The error always looks similar.  Here is an attempt to use sh.exe:

  handle_exceptions: Exception: STATUS_ACCESS_VIOLATION
  stackdump: Dumping stack trace to sh.exe.stackdump
  sync_with_child: child 151(0x6C) died before initialization with status code 0xC0000005
  sync_with_child: *** child state waiting for longjmp

Then the dump itself:

  Exception: STATUS_ACCESS_VIOLATION at eip=610245E3
  eax=00000001 ebx=FFFFFFFF ecx=6108E74C edx=02A50000 esi=0A011304 edi=00000000
  ebp=0241F614 esp=0241F8BC program=C:\unix\bin\sh.exe
  cs=001B ds=0023 es=0023 fs=003B gs=0000 ss=0023
  Stack trace:
  Frame     Function  Args
  0241F614  610245E3  (00000000, 00000000, 00000000, 00000000)
  0241FA34  610245E3  (00000000, 0241FA34, 77F6CD00, 0241FD9C)
  02420000  02423348  (EEFFEEFF, 00000002, 00000000, 0000FE00)
    31464 [main] sh 294 handle_exceptions: Exception: STATUS_ACCESS_VIOLATION
    32081 [main] sh 294 handle_exceptions: Error while dumping state (probably corrupted stack)

Does the Cygwin Unix-on-Win32 code depend on a frame pointer distinct from 
the stack pointer, or is this a bug?

Thanks.

--
Want to unsubscribe from this list?
Check out: http://cygwin.com/ml/#unsubscribe-simple

- Raw text -