Friday, November 9, 2007

Deja vu

So I got a report of a crash today that I tracked down to the Perl interpreter memory allocator:


void* VMem::Malloc(size_t size)
{
2808308A  push        esi  
2808308B  mov         esi,ecx 
#ifdef _USE_LINKED_LIST
    GetLock();
2808308D  mov         eax,dword ptr [esi] 
2808308F  push        edi  
28083090  call        dword ptr [eax+0Ch] 
    PMEMORY_BLOCK_HEADER ptr = (PMEMORY_BLOCK_HEADER)m_pmalloc(size+sizeof(MEMORY_BLOCK_HEADER));
28083093  mov         eax,dword ptr [esp+0Ch] 
28083097  add         eax,0Ch 
2808309A  push        eax  
2808309B  call        dword ptr [esi+34h] 
2808309E  mov         edi,eax 
    LinkBlock(ptr);
280830A0  lea         eax,[esi+4] 
280830A3  pop         ecx  
280830A4  mov         ecx,dword ptr [eax] 
280830A6  mov         dword ptr [eax],edi 
280830A8  mov         dword ptr [edi],ecx
280830AA  mov         dword ptr [edi+4],eax 
280830AD  mov         dword ptr [edi+8],esi 
280830B0  mov         dword ptr [ecx+4],edi 
    FreeLock();
280830B3  mov         eax,dword ptr [esi] 
280830B5  mov         ecx,esi 
280830B7  call        dword ptr [eax+10h] 
    return (ptr+1);
280830BA  lea         eax,[edi+0Ch] 
280830BD  pop         edi  
280830BE  pop         esi  
#else
    return m_pmalloc(size);
#endif

}

EAX = 012C18DC EBX = 01FFFFFB ECX = 21264468 EDX = 0000000A 
ESI = 012C18D8 EDI = 00000000 EIP = 280830A8 ESP = 0271DC70 
EBP = 0271DCA4 EFL = 00000246

And as I'm looking at this, I'm thinking to myself, "doesn't this look familiar?". So I did a search, and came up with the following:

http://rt.perl.org/rt3//Public/Bug/Display.html?id=42648

Then it occurred to me, "oh yeah, it's familiar because I ran across this seven months ago and submitted a patch to Perl core for it." It turns up though that I never checked it in to my own company's source code repository.

So as Dan put it, "You fixed it for everyone in the universe except for us."

Doh.
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