are there any exceptions(cases) that glibc is not strict backward-compatibility?

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are there any exceptions(cases) that glibc is not strict backward-compatibility?

Jason Yang
Dear developers:

I am curious that are there any cases(exceptions) that we need to notice
in terms of glibc backward-compatibility?

I mean glibc is not 100% percentage backward-compatibility, there should
be some cases(exceptions) we need to care about when we use glibc to
implement our own libraries, right?

Where can I find these exceptions?


Regards,

Jason

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Re: are there any exceptions(cases) that glibc is not strict backward-compatibility?

Paul Eggert
On 1/18/20 7:09 AM, Jason Yang wrote:
> are there any cases(exceptions) that we need to notice in
> terms of glibc backward-compatibility?

Every time glibc's behavior changes, there is a potential backward-compatibility
problem. Even if the behavior is just to add a feature that wasn't there before,
it's theoretically possible that old programs assume that the feature is absent
and misbehave if it's present. Plus, old code may depend on buggy glibc behavior
and thus may break when a glibc bug is fixed.

That being said, the glibc developers are quite conscious of
backward-compatibility issues and go to extraordinary lengths to avoid them.

> Where can I find these exceptions?

The source code's top-level NEWS file is a good place to start. Although it
doesn't list *every* backward-compatibility issue, it lists the ones deemed
significant for practical code.
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Re: are there any exceptions(cases) that glibc is not strict backward-compatibility?

Jason Yang
Dear Paul Eggert,

Thank you so much for help!!!

On 2020/01/19 6:52, Paul Eggert wrote:

> On 1/18/20 7:09 AM, Jason Yang wrote:
>> are there any cases(exceptions) that we need to notice in terms of
>> glibc backward-compatibility?
>
> Every time glibc's behavior changes, there is a potential
> backward-compatibility problem. Even if the behavior is just to add a
> feature that wasn't there before, it's theoretically possible that old
> programs assume that the feature is absent and misbehave if it's
> present. Plus, old code may depend on buggy glibc behavior and thus
> may break when a glibc bug is fixed.
>
> That being said, the glibc developers are quite conscious of
> backward-compatibility issues and go to extraordinary lengths to avoid
> them.
>
>> Where can I find these exceptions?
>
> The source code's top-level NEWS file is a good place to start.
> Although it doesn't list *every* backward-compatibility issue, it
> lists the ones deemed significant for practical code.