It started as a test failure on Linux/SPARC64: test-logl.c:42: assertion failed FAIL: test-logl
I tried to fix it by activating the gnulib replacement code for logl(). But the bug persisted. Debugging it in detail, it turned out to be a bug in the 'int' to 'long double' conversion. The glibc provided function, that is invoked by the GCC generated code, actually performs an 'unsigned int' to 'long double' conversion. I've reported it at <http://sources.redhat.com/bugzilla/show_bug.cgi?id=13240>. Here's the workaround for gnulib. 2011-09-30 Bruno Haible <br...@clisp.org> float, math: Fix 'int' to 'long double' conversion on Linux/SPARC64. * m4/float_h.m4 (gl_FLOAT_H): Test conversion from 'int' to 'long double'. Set REPLACE_ITOLD. * lib/float.in.h (_Qp_itoq, _gl_float_fix_itold): New declarations. * lib/math.in.h (_Qp_itoq, _gl_math_fix_itold): New declarations. * lib/itold.c: New file. * modules/float (Files): Add lib/itold.c. (configure.ac): When REPLACE_ITOLD is 1, arrange to compile itold.c. (Makefile.am): Substitute REPLACE_ITOLD. * modules/math (Depends-on): Add float. (Makefile.am): Substitute REPLACE_ITOLD. * doc/posix-headers/float.texi: Mention problem on Linux/SPARC64. * doc/posix-headers/math.texi: Likewise. * doc/posix-functions/logl.texi: Likewise. ================================= lib/itold.c ================================= /* Replacement for 'int' to 'long double' conversion routine. Copyright (C) 2011 Free Software Foundation, Inc. Written by Bruno Haible <br...@clisp.org>, 2011. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. This program 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 General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ #include <config.h> /* Specification. */ #include <float.h> void _Qp_itoq (long double *result, int a) { /* Convert from 'int' to 'double', then from 'double' to 'long double'. */ *result = (double) a; } =============================================================================== --- doc/posix-functions/logl.texi.orig Fri Sep 30 20:59:36 2011 +++ doc/posix-functions/logl.texi Fri Sep 30 20:19:22 2011 @@ -17,6 +17,9 @@ @item This function is not declared on some platforms: MacOS X 10.3. +@item +This function returns wrong results on some platforms: +glibc 2.7 on Linux/SPARC64. @end itemize Portability problems not fixed by Gnulib: --- doc/posix-headers/float.texi.orig Fri Sep 30 20:59:36 2011 +++ doc/posix-headers/float.texi Fri Sep 30 20:47:24 2011 @@ -8,6 +8,10 @@ Portability problems fixed by Gnulib: @itemize @item +The conversion from @code{int} to @code{long double} in incorrect on some +platforms: +glibc 2.7 on Linux/SPARC64. +@item The values of @code{LDBL_*} macros are incorrect on some platforms: On OpenBSD 4.0, MirBSD 10, and BeOS, they are the same as the values of the @code{DBL_*} macros, although @samp{long double} is a larger type than --- doc/posix-headers/math.texi.orig Fri Sep 30 20:59:36 2011 +++ doc/posix-headers/math.texi Fri Sep 30 20:46:58 2011 @@ -8,6 +8,11 @@ Portability problems fixed by Gnulib: @itemize @item +The conversion from @code{int} to @code{long double} in incorrect on some +platforms: +glibc 2.7 on Linux/SPARC64. + +@item The macro @code{NAN} is not defined on some platforms: OpenBSD 4.0, AIX 5.1, IRIX 6.5, OSF/1 5.1. --- lib/float.in.h.orig Fri Sep 30 20:59:36 2011 +++ lib/float.in.h Fri Sep 30 20:51:41 2011 @@ -173,5 +173,16 @@ # endif #endif +#if @REPLACE_ITOLD@ +/* Pull in a function that fixes the 'int' to 'long double' conversion + of glibc 2.7. */ +extern +# ifdef __cplusplus +"C" +# endif +void _Qp_itoq (long double *, int); +static void (*_gl_float_fix_itold) (long double *, int) = _Qp_itoq; +#endif + #endif /* _@GUARD_PREFIX@_FLOAT_H */ #endif /* _@GUARD_PREFIX@_FLOAT_H */ --- lib/math.in.h.orig Fri Sep 30 20:59:36 2011 +++ lib/math.in.h Fri Sep 30 20:51:32 2011 @@ -67,6 +67,14 @@ : rpl_ ## func ## l (value)) +#if @REPLACE_ITOLD@ +/* Pull in a function that fixes the 'int' to 'long double' conversion + of glibc 2.7. */ +_GL_EXTERN_C void _Qp_itoq (long double *, int); +static void (*_gl_math_fix_itold) (long double *, int) = _Qp_itoq; +#endif + + /* POSIX allows platforms that don't support NAN. But all major machines in the past 15 years have supported something close to IEEE NaN, so we define this unconditionally. We also must define --- m4/float_h.m4.orig Fri Sep 30 20:59:36 2011 +++ m4/float_h.m4 Fri Sep 30 20:59:16 2011 @@ -1,4 +1,4 @@ -# float_h.m4 serial 8 +# float_h.m4 serial 9 dnl Copyright (C) 2007, 2009-2011 Free Software Foundation, Inc. dnl This file is free software; the Free Software Foundation dnl gives unlimited permission to copy and/or distribute it, @@ -48,9 +48,51 @@ fi ;; esac + + dnl Test against glibc-2.7 Linux/SPARC64 bug. + REPLACE_ITOLD=0 + AC_CACHE_CHECK([whether conversion from 'int' to 'long double' works], + [gl_cv_func_itold_works], + [ + AC_RUN_IFELSE( + [AC_LANG_SOURCE([[ +int i = -1; +volatile long double ld; +int main () +{ + ld += i * 1.0L; + if (ld > 0) + return 1; + return 0; +}]])], + [gl_cv_func_itold_works=yes], + [gl_cv_func_itold_works=no], + [case "$host" in + sparc*-*-linux*) + AC_EGREP_CPP([yes], + [#if defined __LP64__ || defined __arch64__ + yes + #endif], + [gl_cv_func_itold_works="guessing no"], + [gl_cv_func_itold_works="guessing yes"]) + ;; + *) gl_cv_func_itold_works="guessing yes" ;; + esac + ]) + ]) + case "$gl_cv_func_itold_works" in + *no) + REPLACE_ITOLD=1 + dnl We add the workaround to <float.h> but also to <math.h>, + dnl to increase the chances that the fix function gets pulled in. + FLOAT_H=float.h + ;; + esac + if test -n "$FLOAT_H"; then gl_NEXT_HEADERS([float.h]) fi AC_SUBST([FLOAT_H]) AM_CONDITIONAL([GL_GENERATE_FLOAT_H], [test -n "$FLOAT_H"]) + AC_SUBST([REPLACE_ITOLD]) ]) --- modules/float.orig Fri Sep 30 20:59:36 2011 +++ modules/float Fri Sep 30 20:52:38 2011 @@ -4,6 +4,7 @@ Files: lib/float.in.h lib/float.c +lib/itold.c m4/float_h.m4 Depends-on: @@ -14,6 +15,9 @@ if test $REPLACE_FLOAT_LDBL = 1; then AC_LIBOBJ([float]) fi +if test $REPLACE_ITOLD = 1; then + AC_LIBOBJ([itold]) +fi Makefile.am: BUILT_SOURCES += $(FLOAT_H) @@ -29,6 +33,7 @@ -e 's|@''PRAGMA_SYSTEM_HEADER''@|@PRAGMA_SYSTEM_HEADER@|g' \ -e 's|@''PRAGMA_COLUMNS''@|@PRAGMA_COLUMNS@|g' \ -e 's|@''NEXT_FLOAT_H''@|$(NEXT_FLOAT_H)|g' \ + -e 's|@''REPLACE_ITOLD''@|$(REPLACE_ITOLD)|g' \ < $(srcdir)/float.in.h; \ } > $@-t && \ mv $@-t $@ --- modules/math.orig Fri Sep 30 20:59:36 2011 +++ modules/math Fri Sep 30 20:52:41 2011 @@ -10,6 +10,7 @@ snippet/arg-nonnull snippet/c++defs snippet/warn-on-use +float configure.ac: gl_MATH_H @@ -107,6 +108,7 @@ -e 's|@''REPLACE_ISFINITE''@|$(REPLACE_ISFINITE)|g' \ -e 's|@''REPLACE_ISINF''@|$(REPLACE_ISINF)|g' \ -e 's|@''REPLACE_ISNAN''@|$(REPLACE_ISNAN)|g' \ + -e 's|@''REPLACE_ITOLD''@|$(REPLACE_ITOLD)|g' \ -e 's|@''REPLACE_LDEXPL''@|$(REPLACE_LDEXPL)|g' \ -e 's|@''REPLACE_NAN''@|$(REPLACE_NAN)|g' \ -e 's|@''REPLACE_ROUND''@|$(REPLACE_ROUND)|g' \ -- In memoriam Kelsang Namtso <http://en.wikipedia.org/wiki/Nangpa_La_shooting_incident>
