[PATCH v2] elf: Support DT_RELR relative relocation format [BZ #27924]

[Joseph Myers]

On Mon, 18 Oct 2021, H.J. Lu via Libc-alpha wrote:

> Ideally when the new specifiers are used, it should require the new
> glibc version.  Is there a way to do it?

I don't think there's any sensible way to do it.  You'd need new symbol 
versions (aliased to the old ones, not actual separate entry points with 
different addresses) for all the 70 or so printf-like functions (twice 
that number when two long double variants are supported, three times that 
number when three long double variants are supported).  That's not 
something we've done before for new printf/scanf/strftime/strfmon formats.

The scanf changes will get new __isoc23_* entry points because of API 
differences with scanf %i (but someone could still e.g. use scanf %b when 
building for strict C11, and so get a binary using the old entry point 
with a new format that doesn't work with older glibc - there would only be 
the 32 / 44 / 56 new entry points, not new symbol versions for old entry 
points).

-- 
Joseph S. Myers
joseph@codesourcery.com