[LLVMdev] proposal to avoid zlib dependency.

[Yaron Keren]

Hi,

There are very good reasons why packaging an external library is a big
headache in general.
However, for zlib it's not so bad for several reasons.

1 zlib is stable, code and file format. The last release is 1.5 years old.
Manually updating the zlib sources once or twice a  year is trivial.

2 For llvm, there should not be a problem with possible security exploits
forcing quick patch, as long zlib is used to encode debug information
coming from llvm.

3 gdb uses the system zlib library of which there are many outdated copies
around, so gdb can not expect to have the latest zlib. Thus, even if we
miss an update, it's not likely to be a real problem.

Yaron


2014-09-18 10:48 GMT+03:00 Chandler Carruth <chandlerc at google.com>:

> FWIW, I strongly support finding a fully license-compatible way to just
> implement zlib-compatible compression with no external library dependencies.
>
> There are a myriad of reasons, some already raised:
>
> - Means that functionality isn't universally available, for example, on
> Windows
> - Means that we have to debug performance problems or other issues with
> different source code depending on the nature of specific libraries used
>
> If the cost is low (and it seems low for miniz or zlib or whatever) why go
> through the hassle of using a system library....
>
> On Tue, Sep 16, 2014 at 7:11 PM, Saleem Abdulrasool <compnerd at compnerd.org
> > wrote:
>
>> On Tue, Sep 16, 2014 at 4:48 PM, Bob Wilson <bob.wilson at apple.com> wrote:
>>
>>> If you build with configure+make, just run configure with --disable-zlib.
>>> We do this routinely, so I'm pretty sure it works.
>>>
>>
>> It "works" as in it builds.  However, the support for it is disabled
>> since zlib::compress will always return StatusUnsupported, so the debug
>> information will just not be compressed.  Effectively, compressed DWARF is
>> unsupported on Windows.
>>
>>
>>> On Sep 16, 2014, at 3:42 PM, Reid Kleckner <rnk at google.com> wrote:
>>>
>>> It might not be available, so all codepaths have to recover from zlib
>>> unavailability. For example, I don't think compressed DWARF works on
>>> Windows.
>>>
>>> On Tue, Sep 16, 2014 at 3:21 PM, Filip Pizlo <fpizlo at apple.com> wrote:
>>>
>>>> What is the downside of Zlib dependency?  I'm curious! :-)
>>>>
>>>> -Filip
>>>>
>>>> On Sep 16, 2014, at 2:45 PM, Christophe Duvernois <
>>>> christophe.duvernois at gmail.com> wrote:
>>>>
>>>> Hi
>>>>
>>>> Miniz (https://code.google.com/p/miniz/ ) is very small and performant
>>>> implementation of zlib compression with api compatibility and it is public
>>>> domain...
>>>> Miniz can be integrated directly into the llvm source code.
>>>> So it could be a good replacement or alternative to avoid zlib
>>>> dependency...
>>>>
>>>> If someone is interested i can provide a patch.
>>>>
>>>> Regards
>>>> Christophe
>>>>
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>>
>>
>> --
>> Saleem Abdulrasool
>> compnerd (at) compnerd (dot) org
>>
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>>
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