[H-GEN] Apache segfaulting... how to debug

[Andrae Muys]

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Michael Anthon wrote:
> bash> ldd /usr/lib/php4/20020429/oci8.so
>         libclntsh.so.8.0 => /oracle/as9i/lib/libclntsh.so.8.0 (0x40010000)
>         libc.so.6 => /lib/libc.so.6 (0x405d6000)
>         libwtc8.so => /oracle/as9i/lib/libwtc8.so (0x406e6000)
>         libdl.so.2 => /lib/libdl.so.2 (0x406ee000)
>         libm.so.6 => /lib/libm.so.6 (0x406f1000)
>         libpthread.so.0 => /lib/libpthread.so.0 (0x40712000)
>         /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x80000000)
> 
> If I understand the gist of what Andrae is saying then you are 
> suggesting that something is allocating some memory but not cleaning up 
> after itself?
> 

The memory allocator keeps various records about allocated memory that 
allow it to manage allocations, reallocations, and deallocations.  If 
this data gets clobbered for whatever reason your application can crash 
at weird places (such as after returning from main, or inside 
malloc/free) as the allocator wanders off in search of some random 
garbage address.

The most common cause for this sort of behaviour I have seen is to free 
the same block of memory twice --- on some allocators this will lead to 
a crash in some indeterminate malloc/free later in the program --- 
however heap array overruns/underruns; random pointer fandangos; 
incompatible libc's/allocators; could all conceivably cause the same 
symptoms.

Check apache and make sure it is linked against /lib/libc.so.6.  Other 
than that you could try providing an ltrace, although this would likely 
have security implications if you accessed anything sensitive.  (You 
might also like to check the strace for any sensitive information that 
might need sanitising).

Andrae



-- 
Andrae Muys                       But can it generate *quantum* Haiku
<andrae.muys at braintree.com.au>    error messages, in Latin, where each
Engineer                          line of the error message is a
Braintree Communications          palindrome? -- Mike Vanier on perl



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