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Re: [PATCH 4/4] Use compat_symbol for _finite symbols
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>
- Cc: "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>, nd <nd at arm dot com>
- Date: Wed, 24 Jul 2019 21:02:15 +0000
- Subject: Re: [PATCH 4/4] Use compat_symbol for _finite symbols
- References: <VI1PR0801MB212721B4E319BCD582BF0BFD83E20@VI1PR0801MB2127.eurprd08.prod.outlook.com>
On Wed, 26 Jun 2019, Wilco Dijkstra wrote:
> diff --git a/sysdeps/ieee754/float128/float128_private.h b/sysdeps/ieee754/float128/float128_private.h
> index f3917b463837e9eb19d18c62ba232d9bb077e9a1..c7bb208efb024030f0ae7cc71a01dab1d42c4fa1 100644
> --- a/sysdeps/ieee754/float128/float128_private.h
> +++ b/sysdeps/ieee754/float128/float128_private.h
> @@ -365,3 +365,12 @@ mul_splitf128 (_Float128 *hi, _Float128 *lo, _Float128 x, _Float128 y)
> *lo = (((x1 * y1 - *hi) + x1 * y2) + x2 * y1) + x2 * y2;
> #endif
> }
> +
> +/* Ensure compat_symbol uses GLIBC_2_26 since that was when the
> + __<fn>f128_finite symbols were introduced. */
> +#include <shlib-compat.h>
> +#if SHLIB_COMPAT (libm, GLIBC_2_26, GLIBC_2_30)
> +# undef compat_symbol
> +# define compat_symbol(lib, local, symbol, version) \
> + compat_symbol_reference (lib, local, symbol, GLIBC_2_26)
> +#endif
This is implicitly embedding an action-at-a-distance assumption that the
only case for using compat_symbol in float128 code is for functions added
in 2.26 and obsoleted in 2.30. That seems excessively fragile to me.
How about having
#define FINITE_VERSION GLIBC_2_15
somewhere, with float128_private.h overriding that to GLIBC_2_26, and then
all the relevant SHLIB_COMPAT and compat_symbol calls using FINITE_VERSION
instead of GLIBC_2_15? That way you avoid causing nonobvious problems for
any post-2.26 *f128 symbols that might get obsoleted in future.
--
Joseph S. Myers
joseph@codesourcery.com