Mercurial > gnulib
view m4/log2.m4 @ 37246:5cfb3a67238d
regex: avoid glibc deadlock during configure
glibc has a known bug where certain corruptions of the heap can
cause malloc to default to printing a debug message that includes
a backtrace, but the act of getting the backtrace uses dlopen
which in turn calls into malloc, causing a recursive lock ending
in deadlock. Thus, when configure is probing for a known glibc
heap corruption bug, the overall configure would hang.
The solution suggested by glibc developers is to force malloc
to quit printing debug messages, which avoids recursive malloc.
* m4/regex.m4 (gl_REGEX): Avoid recursive malloc deadlock when
glibc bug 15078 in turn triggers bug 16159.
Reported by Michal Privoznik.
Signed-off-by: Eric Blake <eblake@redhat.com>
author | Eric Blake <eblake@redhat.com> |
---|---|
date | Tue, 03 Dec 2013 10:34:13 -0700 |
parents | c741bc27922a |
children | 344018b6e5d7 |
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# log2.m4 serial 3 dnl Copyright (C) 2010-2013 Free Software Foundation, Inc. dnl This file is free software; the Free Software Foundation dnl gives unlimited permission to copy and/or distribute it, dnl with or without modifications, as long as this notice is preserved. AC_DEFUN([gl_FUNC_LOG2], [ m4_divert_text([DEFAULTS], [gl_log2_required=plain]) AC_REQUIRE([gl_MATH_H_DEFAULTS]) dnl Persuade glibc <math.h> to declare log2(). AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS]) dnl Determine LOG2_LIBM. gl_COMMON_DOUBLE_MATHFUNC([log2]) dnl Test whether log2() exists. save_LIBS="$LIBS" LIBS="$LIBS $LOG2_LIBM" AC_CHECK_FUNCS([log2]) LIBS="$save_LIBS" if test $ac_cv_func_log2 = yes; then HAVE_LOG2=1 dnl Also check whether it's declared. dnl IRIX 6.5 has log2() in libm but doesn't declare it in <math.h>. AC_CHECK_DECL([log2], , [HAVE_DECL_LOG2=0], [[#include <math.h>]]) save_LIBS="$LIBS" LIBS="$LIBS $LOG2_LIBM" gl_FUNC_LOG2_WORKS LIBS="$save_LIBS" case "$gl_cv_func_log2_works" in *yes) ;; *) REPLACE_LOG2=1 ;; esac m4_ifdef([gl_FUNC_LOG2_IEEE], [ if test $gl_log2_required = ieee && test $REPLACE_LOG2 = 0; then AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles AC_CACHE_CHECK([whether log2 works according to ISO C 99 with IEC 60559], [gl_cv_func_log2_ieee], [ save_LIBS="$LIBS" LIBS="$LIBS $LOG2_LIBM" AC_RUN_IFELSE( [AC_LANG_SOURCE([[ #ifndef __NO_MATH_INLINES # define __NO_MATH_INLINES 1 /* for glibc */ #endif #include <math.h> #ifndef log2 /* for Cygwin 1.7.x */ extern #ifdef __cplusplus "C" #endif double log2 (double); #endif /* Compare two numbers with ==. This is a separate function because IRIX 6.5 "cc -O" miscompiles an 'x == x' test. */ static int numeric_equal (double x, double y) { return x == y; } static double dummy (double x) { return 0; } int main (int argc, char *argv[]) { double (*my_log2) (double) = argc ? log2 : dummy; /* Test log2(negative). This test fails on NetBSD 5.1 and Solaris 11 2011-11. */ double y = my_log2 (-1.0); if (numeric_equal (y, y)) return 1; return 0; } ]])], [gl_cv_func_log2_ieee=yes], [gl_cv_func_log2_ieee=no], [case "$host_os" in # Guess yes on glibc systems. *-gnu*) gl_cv_func_log2_ieee="guessing yes" ;; # If we don't know, assume the worst. *) gl_cv_func_log2_ieee="guessing no" ;; esac ]) LIBS="$save_LIBS" ]) case "$gl_cv_func_log2_ieee" in *yes) ;; *) REPLACE_LOG2=1 ;; esac fi ]) else HAVE_LOG2=0 HAVE_DECL_LOG2=0 fi if test $HAVE_LOG2 = 0 || test $REPLACE_LOG2 = 1; then dnl Find libraries needed to link lib/log2.c. AC_REQUIRE([gl_FUNC_ISNAND]) AC_REQUIRE([gl_FUNC_FREXP]) AC_REQUIRE([gl_FUNC_LOG]) LOG2_LIBM= dnl Append $ISNAND_LIBM to LOG2_LIBM, avoiding gratuitous duplicates. case " $LOG2_LIBM " in *" $ISNAND_LIBM "*) ;; *) LOG2_LIBM="$LOG2_LIBM $ISNAND_LIBM" ;; esac dnl Append $FREXP_LIBM to LOG2_LIBM, avoiding gratuitous duplicates. case " $LOG2_LIBM " in *" $FREXP_LIBM "*) ;; *) LOG2_LIBM="$LOG2_LIBM $FREXP_LIBM" ;; esac dnl Append $LOG_LIBM to LOG2_LIBM, avoiding gratuitous duplicates. case " $LOG2_LIBM " in *" $LOG_LIBM "*) ;; *) LOG2_LIBM="$LOG2_LIBM $LOG_LIBM" ;; esac fi ]) dnl Test whether log2() works. dnl On OSF/1 5.1, log2(-0.0) is NaN. dnl On Cygwin 1.7.9, log2(2^29) is not exactly 29. AC_DEFUN([gl_FUNC_LOG2_WORKS], [ AC_REQUIRE([AC_PROG_CC]) AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles AC_CACHE_CHECK([whether log2 works], [gl_cv_func_log2_works], [ AC_RUN_IFELSE( [AC_LANG_SOURCE([[ #include <math.h> #ifndef log2 /* for Cygwin 1.7.x */ extern #ifdef __cplusplus "C" #endif double log2 (double); #endif volatile double x; volatile double y; int main () { int result = 0; /* This test fails on OSF/1 5.1. */ x = -0.0; y = log2 (x); if (!(y + y == y)) result |= 1; /* This test fails on Cygwin 1.7.9. */ x = 536870912.0; y = log2 (x); if (!(y == 29.0)) result |= 2; return result; } ]])], [gl_cv_func_log2_works=yes], [gl_cv_func_log2_works=no], [case "$host_os" in cygwin* | osf*) gl_cv_func_log2_works="guessing no";; *) gl_cv_func_log2_works="guessing yes";; esac ]) ]) ])