log1pl lacks precision on musl libc 1.2.2/arm64, musl libc 1.2.2/s390x. This patch adds a configure test, that enables a gnulib workaround.
2021-01-31 Bruno Haible <br...@clisp.org> log1pl: Work around musl libc bug. * doc/posix-functions/log1pl.texi: Document musl libc bug. * m4/log1pl.m4 (gl_FUNC_LOG1PL_WORKS): New macro. (gl_FUNC_LOG1PL): Invoke it. diff --git a/doc/posix-functions/log1pl.texi b/doc/posix-functions/log1pl.texi index 802c2e6..be81d60 100644 --- a/doc/posix-functions/log1pl.texi +++ b/doc/posix-functions/log1pl.texi @@ -11,6 +11,10 @@ Portability problems fixed by either Gnulib module @code{log1pl} or @code{log1pl @item This function is missing on some platforms: FreeBSD 6.0, NetBSD 9.0, OpenBSD 3.8, Minix 3.1.8, AIX 5.1, HP-UX 11, IRIX 6.5, Solaris 9, Cygwin 1.7.x, MSVC 9, Android 4.4. +@item +This function produces results which are accurate to only 16 digits on some +platforms: +musl libc 1.2.2/arm64, musl libc 1.2.2/s390x. @end itemize Portability problems fixed by Gnulib module @code{log1pl-ieee}: diff --git a/m4/log1pl.m4 b/m4/log1pl.m4 index 7d95aac..bd9d63d 100644 --- a/m4/log1pl.m4 +++ b/m4/log1pl.m4 @@ -1,4 +1,4 @@ -# log1pl.m4 serial 8 +# log1pl.m4 serial 9 dnl Copyright (C) 2012-2021 Free Software Foundation, Inc. dnl This file is free software; the Free Software Foundation dnl gives unlimited permission to copy and/or distribute it, @@ -22,6 +22,16 @@ AC_DEFUN([gl_FUNC_LOG1PL], LIBS="$save_LIBS" if test $ac_cv_func_log1pl = yes; then LOG1PL_LIBM="$LOG1P_LIBM" + + save_LIBS="$LIBS" + LIBS="$LIBS $LOG1PL_LIBM" + gl_FUNC_LOG1PL_WORKS + LIBS="$save_LIBS" + case "$gl_cv_func_log1pl_works" in + *yes) ;; + *) REPLACE_LOG1PL=1 ;; + esac + m4_ifdef([gl_FUNC_LOG1PL_IEEE], [ if test $gl_log1pl_required = ieee && test $REPLACE_LOG1PL = 0; then AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles @@ -99,3 +109,93 @@ int main (int argc, char *argv[]) fi AC_SUBST([LOG1PL_LIBM]) ]) + +dnl Test whether log1pl() works. +dnl On musl 1.2.2/{arm64,s390x}, the result is accurate to only 16 digits. +AC_DEFUN([gl_FUNC_LOG1PL_WORKS], +[ + AC_REQUIRE([AC_PROG_CC]) + AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles + AC_CACHE_CHECK([whether log1pl works], [gl_cv_func_log1pl_works], + [ + AC_RUN_IFELSE( + [AC_LANG_SOURCE([[ +#ifndef __NO_MATH_INLINES +# define __NO_MATH_INLINES 1 /* for glibc */ +#endif +#include <float.h> +#include <math.h> +/* Override the values of <float.h>, like done in float.in.h. */ +#if defined __i386__ && (defined __BEOS__ || defined __OpenBSD__) +# undef LDBL_MANT_DIG +# define LDBL_MANT_DIG 64 +# undef LDBL_MIN_EXP +# define LDBL_MIN_EXP (-16381) +# undef LDBL_MAX_EXP +# define LDBL_MAX_EXP 16384 +#endif +#if defined __i386__ && (defined __FreeBSD__ || defined __DragonFly__) +# undef LDBL_MANT_DIG +# define LDBL_MANT_DIG 64 +# undef LDBL_MIN_EXP +# define LDBL_MIN_EXP (-16381) +# undef LDBL_MAX_EXP +# define LDBL_MAX_EXP 16384 +#endif +#if (defined _ARCH_PPC || defined _POWER) && defined _AIX && (LDBL_MANT_DIG == 106) && defined __GNUC__ +# undef LDBL_MIN_EXP +# define LDBL_MIN_EXP DBL_MIN_EXP +#endif +#if defined __sgi && (LDBL_MANT_DIG >= 106) +# undef LDBL_MANT_DIG +# define LDBL_MANT_DIG 106 +# if defined __GNUC__ +# undef LDBL_MIN_EXP +# define LDBL_MIN_EXP DBL_MIN_EXP +# endif +#endif +#undef log1pl +extern +#ifdef __cplusplus +"C" +#endif +long double log1pl (long double); +static long double dummy (long double x) { return 0; } +int main (int argc, char *argv[]) +{ + long double (* volatile my_log1pl) (long double) = argc ? log1pl : dummy; + int result = 0; + /* This test fails on musl 1.2.2/arm64, musl 1.2.2/s390x. */ + { + const long double TWO_LDBL_MANT_DIG = /* 2^LDBL_MANT_DIG */ + (long double) (1U << ((LDBL_MANT_DIG - 1) / 5)) + * (long double) (1U << ((LDBL_MANT_DIG - 1 + 1) / 5)) + * (long double) (1U << ((LDBL_MANT_DIG - 1 + 2) / 5)) + * (long double) (1U << ((LDBL_MANT_DIG - 1 + 3) / 5)) + * (long double) (1U << ((LDBL_MANT_DIG - 1 + 4) / 5)); + long double x = 11.358L; + long double y = my_log1pl (x); + long double z = my_log1pl (- x / (1.0L + x)); + long double err = (y + z) * TWO_LDBL_MANT_DIG; + if (!(err >= -900.0L && err <= 900.0L)) + result |= 1; + } + + return result; +} +]])], + [gl_cv_func_log1pl_works=yes], + [gl_cv_func_log1pl_works=no], + [case "$host_os" in + # Guess yes on glibc systems. + *-gnu* | gnu*) gl_cv_func_log1pl_works="guessing yes" ;; + # Guess no on musl systems. + *-musl*) gl_cv_func_log1pl_works="guessing no" ;; + # Guess yes on native Windows. + mingw*) gl_cv_func_log1pl_works="guessing yes" ;; + # If we don't know, obey --enable-cross-guesses. + *) gl_cv_func_log1pl_works="$gl_cross_guess_normal" ;; + esac + ]) + ]) +])