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Mike Frysinger wrote:
> On Friday 17 July 2009 01:36:37 Carmelo AMOROSO wrote:
>> I've recently added for testing hidden_proto in {m,re,c}alloc functions to
>> ensure that from within the libc we always called the hidden __GI_xxx
>> symbols.
>>
>> Using this uClibc with firefox and bash I found a problem.
>> Both bash and firefox provide a their own implementation of memory
>> allocation functions (bash internally, firefox by libejmalloc.so).
>>
>> Because the dynamic linker will search undefined symbols firstly in the
>> application, any reference to malloc/free functions will be resolved by the
>> application's symbols.
>>
>> If we use the hidden_protos, calls to malloc/free from libc are resolved
>> inside libc itslef at it is expected.
>>
>> Now we have getcwd and strdup that use malloc for allocate memory and
>> return the pointer to the caller. This memory is after freed by the
>> application, calling free(), that is not the libc one implementation,
>> leading to error, sigbus and so on.
>>
>> Do you think it is wrong to use the hidden_protos for this class of
>> functions, or we should think better at how internal symbols are actually
>> used by uClibc ?
>
Hi Mike,
> i didnt quite understand this e-mail originally. i thought you were saying
> you added tests only, not that you also added the hidden aliases to the
> allocation functions.
I added them indeed,
> if you want to make a new config option ("Allow malloc
> to be overridden dynamically"), that's fine.
No, I don't.
> but the default should be what
> we have today -- the malloc symbols can be resolved dynamically at runtime.
> this is how many debugging libraries work in the first place -- they provide
> the malloc() and related symbols.
>
this is the answer I was looking for. I thought to remove the relocation for
malloc too,
but I was wrong.
> i dont know what you mean by "think better" as the current stuff should be
> correct already. the number of relocs in the C library is very small for
> functions which is the point of these hidden aliases.
> looking at latest git i
> see one or two missing, but those should be easy to fix.
> -mike
Thanks a lot.
Carmelo
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