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bug#16986: Fw: Re: Crash when idle
From: |
Dmitry Antipov |
Subject: |
bug#16986: Fw: Re: Crash when idle |
Date: |
Fri, 01 Aug 2014 12:17:31 +0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 |
On 07/23/2014 02:09 PM, YAMAMOTO Mitsuharu wrote:
I suspect there are no direct references to the value of `directory'
from stack contents or register values, and thus GC triggered by the
above DECODE_FILE has collected the value of `directory' as a garbage.
If that is the case, %rax at <+730> (i.e., &XSTRING(directory)->data)
would become invalid.
Nice shot.
Clang 3.4 with -O2 -g3 generates:
0x0000000000531c21 <+721>: callq 0x551570 <make_uninit_multibyte_string>
0x0000000000531c26 <+726>: mov %rax,%rbp
0x0000000000531c29 <+729>: mov 0x17(%rbp),%rdi
0x0000000000531c2d <+733>: mov 0x28(%rsp),%rax
0x0000000000531c32 <+738>: mov (%rax),%rsi
0x0000000000531c35 <+741>: mov 0x38(%rsp),%rdx
0x0000000000531c3a <+746>: callq 0x413050 <memcpy@plt>
GCC 4.8.3 with -O2 -g3 generates:
0x0000000000520e0d <+573>: callq 0x5407e0 <make_uninit_multibyte_string>
0x0000000000520e12 <+578>: mov 0x38(%rsp),%rsi
0x0000000000520e17 <+583>: lea -0x1(%rax),%r15
0x0000000000520e1b <+587>: mov 0x20(%rsp),%rdx
0x0000000000520e20 <+592>: mov 0x18(%r15),%rdi
0x0000000000520e24 <+596>: mov %rax,%rbx
0x0000000000520e27 <+599>: mov 0x18(%rsi),%rsi
0x0000000000520e2b <+603>: callq 0x413270 <memcpy@plt>
With an attached patch, clang generates:
0x0000000000531c01 <+689>: callq 0x551560 <make_uninit_multibyte_string>
0x0000000000531c06 <+694>: mov 0x17(%rax),%rdi
0x0000000000531c0a <+698>: mov %rax,%rbp
0x0000000000531c0d <+701>: mov 0x68(%rsp),%rax
0x0000000000531c12 <+706>: mov 0x17(%rax),%rsi
0x0000000000531c16 <+710>: mov 0x50(%rsp),%rdx
0x0000000000531c1b <+715>: callq 0x413050 <memcpy@plt>
I.e. with a displacement to %rsi. OK to install?
Dmitry
bug16986.patch
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