[PATCH v3] libio: use PTR_MANGLE/PTR_DEMANGLE for FILE vtables

[Florian Weimer]

On 05/25/2016 07:52 PM, Mike Frysinger wrote:
> On 25 May 2016 10:29, Florian Weimer wrote:
>> I think we need a follow-up patch which removes the symbols which are
>> now incompatible from the ABI, so that programs which are broken by this
>> configuration receive an explicit error message.
>
> you mean all of the _IO_* symbols ?

There are exceptions which are part of the API.  At least _IO_putc and 
_IO_getc are, and _IO_stdin_used is interposed from the application. 
(We can maybe get rid of the latter because it does not work anyway 
because nothing ensures that the program is compiled against a 
consistent set of libio definitions.)

> my familiarity here is like 0,

Sadly, I don't know if we can pick anyone's brain who is more familiar 
with these details.

> but are there any reasons to keep exporting those for new ABIs ?

For most symbols, no, there is no reason to keep them for new ABIs.

My understanding of symbol versioning is still limited, and I have no 
clear picture of the minimal libio ABI we can export, otherwise I'd have 
sent some patches long ago.

A first step would involve cutting down the contents of the installed 
<libio.h> header file to the absolute minimum needed by <stdio.h>.  But 
even that is quite a bit of work.

Florian