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*From*: Joseph Myers <joseph at codesourcery dot com>*To*: <libc-alpha at sourceware dot org>*Date*: Wed, 23 Nov 2016 00:30:26 +0000*Subject*: Fix default float_t definition (bug 20855)*Authentication-results*: sourceware.org; auth=none

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 <https://sourceware.org/ml/libc-alpha/2015-01/msg00499.html>, 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 #include this test but compile it with other options.) 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 <https://sourceware.org/ml/libc-alpha/2016-11/msg00745.html>, which will create as few header variants as possible for each group of definitions. Tested (compilation only) with build-many-glibcs.py. 2016-11-23 Joseph Myers <joseph@codesourcery.com> [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. diff --git a/NEWS b/NEWS index b99fc69..6e256ae 100644 --- a/NEWS +++ b/NEWS @@ -65,6 +65,11 @@ Version 2.25 - NaN functions: getpayload, getpayloadf, getpayloadl, setpayload, setpayloadf, setpayloadl. +* On ColdFire, MicroBlaze, Nios II and SH3, the float_t type is now defined + to float instead of double. This does not affect the ABI of any libraries + that are part of the GNU C Library, but may affect the ABI of other + libraries that use this type in their interfaces. + * The functions strfromd, strfromf, and strfroml, from ISO/IEC TS 18661-1:2014, are added to libc. They convert a floating-point number into string. diff --git a/bits/mathdef.h b/bits/mathdef.h index c5d5f8c..d557d08 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'. */ diff --git a/math/Makefile b/math/Makefile index a5b11e9..fe910ef 100644 --- a/math/Makefile +++ b/math/Makefile @@ -158,7 +158,7 @@ tests = test-matherr test-fenv atest-exp atest-sincos atest-exp2 basic-test \ test-fexcept test-fexcept-traps test-fesetexcept \ test-fesetexcept-traps test-fetestexceptflag test-femode \ test-femode-traps test-iszero-excess-precision \ - test-iseqsig-excess-precision $(tests-static) + test-iseqsig-excess-precision test-flt-eval-method $(tests-static) tests-static = test-fpucw-static test-fpucw-ieee-static \ test-signgam-uchar-static test-signgam-uchar-init-static \ test-signgam-uint-static test-signgam-uint-init-static \ @@ -271,6 +271,7 @@ CFLAGS-test-math-iszero.cc = -std=gnu++11 CFLAGS-test-iszero-excess-precision.c = -fexcess-precision=standard CFLAGS-test-iseqsig-excess-precision.c = -fexcess-precision=standard +CFLAGS-test-flt-eval-method.c = -fexcess-precision=standard # The -lieee module sets the _LIB_VERSION_ switch to IEEE mode # for error handling in the -lm functions. diff --git a/math/test-flt-eval-method.c b/math/test-flt-eval-method.c new file mode 100644 index 0000000..84706a5 --- /dev/null +++ b/math/test-flt-eval-method.c @@ -0,0 +1,65 @@ +/* Test evaluation method typedefs match FLT_EVAL_METHOD. + Copyright (C) 2016 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#include <float.h> +#include <math.h> + +#if FLT_EVAL_METHOD == -1 +/* Cannot test. */ +typedef float_t my_float_t; +typedef double_t my_double_t; +#elif FLT_EVAL_METHOD == 0 || FLT_EVAL_METHOD == 16 +typedef float my_float_t; +typedef double my_double_t; +#elif FLT_EVAL_METHOD == 1 +typedef double my_float_t; +typedef double my_double_t; +#elif FLT_EVAL_METHOD == 2 +typedef long double my_float_t; +typedef long double my_double_t; +#elif FLT_EVAL_METHOD == 32 +typedef _Float32 my_float_t; +typedef double my_double_t; +#elif FLT_EVAL_METHOD == 33 +typedef _Float32x my_float_t; +typedef _Float32x my_double_t; +#elif FLT_EVAL_METHOD == 64 +typedef _Float64 my_float_t; +typedef _Float64 my_double_t; +#elif FLT_EVAL_METHOD == 65 +typedef _Float64x my_float_t; +typedef _Float64x my_double_t; +#elif FLT_EVAL_METHOD == 128 +typedef _Float128 my_float_t; +typedef _Float128 my_double_t; +#elif FLT_EVAL_METHOD == 129 +typedef _Float128x my_float_t; +typedef _Float128x my_double_t; +#else +# error "Unknown FLT_EVAL_METHOD" +#endif + +extern float_t test_float_t; +extern my_float_t test_float_t; + +extern double_t test_double_t; +extern my_double_t test_double_t; + +/* This is a compilation test. */ +#define TEST_FUNCTION 0 +#include "../test-skeleton.c" -- Joseph S. Myers joseph@codesourcery.com

**Follow-Ups**:**Re: Fix default float_t definition (bug 20855)***From:*Joseph Myers

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