From b0216d3e4d98a3528bad428c22ff96fcbcc102a4 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Wed, 23 Nov 2016 00:28:30 +0000 Subject: Fix default float_t definition (bug 20855). The default (top-level) version of bits/mathdef.h defines float_t to double. It is used on ColdFire, MicroBlaze, Nios II and SH3, all of which define FLT_EVAL_METHOD to 0, so float_t should be float (and C11 requires a certain correspondence between these typedefs and FLT_EVAL_METHOD values). I proposed fixing this default in , with no objections from architecture maintainers, and this patch makes that fix. As noted in the NEWS entry added, this might affect the ABIs of non-glibc libraries (ImageMagick has been mentioned in gcc-patches discussion of the S/390 case - which is unaffected by this patch), but as noted in my previous message, affected libraries would have problems with -mfpmath=sse anyway on 32-bit x86. A (compilation) testcase is added to verify the required correspondence of typedefs to FLT_EVAL_METHOD values. This test is built with -fexcess-precision=standard to avoid any issues with GCC 7 on S/390 providing a more accurate FLT_EVAL_METHOD definition in the default (no excess precision) mode. (This will also be usable to test a fix for the recently reported bug about these typedefs on x86_64 -mfpmath=387, as architecture-specific tests can be added that It is entirely possible that the fixed default makes some architecture-specific versions of bits/mathdef.h semantically equivalent to the default version and so no longer required. I don't intend to investigate that separately from the refactoring I proposed in , which will create as few header variants as possible for each group of definitions. Tested (compilation only) with build-many-glibcs.py. [BZ #20855] * bits/mathdef.h (float_t): Define to float. * math/test-flt-eval-method.c: New file. * math/Makefile (tests): Add test-flt-eval-method. (CFLAGS-test-flt-eval-method.c): New variable. --- bits/mathdef.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'bits/mathdef.h') diff --git a/bits/mathdef.h b/bits/mathdef.h index c5d5f8c0a8..d557d08582 100644 --- a/bits/mathdef.h +++ b/bits/mathdef.h @@ -22,10 +22,10 @@ #if defined __USE_ISOC99 && defined _MATH_H && !defined _MATH_H_MATHDEF # define _MATH_H_MATHDEF 1 -/* Normally, there is no long double type and the `float' and `double' - expressions are evaluated as `double'. */ -typedef double float_t; /* `float' expressions are evaluated as - `double'. */ +/* Expressions are evaluated with the range and precision of their + type. */ +typedef float float_t; /* `float' expressions are evaluated as + `float'. */ typedef double double_t; /* `double' expressions are evaluated as `double'. */ -- cgit v1.2.1