diff options
Diffstat (limited to 'configure.in')
| -rw-r--r-- | configure.in | 41 |
1 files changed, 40 insertions, 1 deletions
diff --git a/configure.in b/configure.in index 394c804..d80e7a7 100644 --- a/configure.in +++ b/configure.in @@ -3056,6 +3056,44 @@ fi], LIBS_SAVE=$LIBS LIBS="$LIBS $LIBM" +# Detect whether system arithmetic is subject to x87-style double +# rounding issues. The result of this test has little meaning on non +# IEEE 754 platforms. On IEEE 754, test should return 1 if rounding +# mode is round-to-nearest and double rounding issues are present, and +# 0 otherwise. See http://bugs.python.org/issue2937 for more info. +AC_MSG_CHECKING(for x87-style double rounding) +AC_CACHE_VAL(ac_cv_x87_double_rounding, [ +AC_TRY_RUN([ +#include <stdlib.h> +#include <math.h> +int main() { + volatile double x, y, z; + /* 1./(1-2**-53) -> 1+2**-52 (correct), 1.0 (double rounding) */ + x = 0.99999999999999989; /* 1-2**-53 */ + y = 1./x; + if (y != 1.) + exit(0); + /* 1e16+2.99999 -> 1e16+2. (correct), 1e16+4. (double rounding) */ + x = 1e16; + y = 2.99999; + z = x + y; + if (z != 1e16+4.) + exit(0); + /* both tests show evidence of double rounding */ + exit(1); +} +], +ac_cv_x87_double_rounding=no, +ac_cv_x87_double_rounding=yes, +ac_cv_x87_double_rounding=no)]) +AC_MSG_RESULT($ac_cv_x87_double_rounding) +if test "$ac_cv_x87_double_rounding" = yes +then + AC_DEFINE(X87_DOUBLE_ROUNDING, 1, + [Define if arithmetic is subject to x87-style double rounding issue]) +fi + + # On FreeBSD 6.2, it appears that tanh(-0.) returns 0. instead of # -0. on some architectures. AC_MSG_CHECKING(whether tanh preserves the sign of zero) @@ -3084,7 +3122,8 @@ fi AC_REPLACE_FUNCS(hypot) -AC_CHECK_FUNCS(acosh asinh atanh copysign expm1 finite isinf isnan log1p) +AC_CHECK_FUNCS([acosh asinh atanh copysign expm1 finite log1p]) +AC_CHECK_DECLS([isinf, isnan, isfinite], [], [], [[#include <math.h>]]) LIBS=$LIBS_SAVE |