log10: Work around OSF/1 5.1 bug.

[gnulib.git] / m4 / log10.m4

diff --git a/m4/log10.m4 b/m4/log10.m4
index 251c1c6..ab066cc 100644 (file)
--- a/m4/log10.m4
+++ b/m4/log10.m4
@@ -1,4 +1,4 @@
-# log10.m4 serial 1
+# log10.m4 serial 2
 dnl Copyright (C) 2011-2012 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,6 +6,49 @@ dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN([gl_FUNC_LOG10],
 [
+  AC_REQUIRE([gl_MATH_H_DEFAULTS])
+
   dnl Determine LOG10_LIBM.
   gl_COMMON_DOUBLE_MATHFUNC([log10])
+
+  save_LIBS="$LIBS"
+  LIBS="$LIBS $LOG10_LIBM"
+  gl_FUNC_LOG10_WORKS
+  LIBS="$save_LIBS"
+  case "$gl_cv_func_log10_works" in
+    *yes) ;;
+    *) REPLACE_LOG10=1 ;;
+  esac
+])
+
+dnl Test whether log10() works.
+dnl On OSF/1 5.1, log10(-0.0) is NaN.
+AC_DEFUN([gl_FUNC_LOG10_WORKS],
+[
+  AC_REQUIRE([AC_PROG_CC])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  AC_CACHE_CHECK([whether log10 works], [gl_cv_func_log10_works],
+    [
+      AC_RUN_IFELSE(
+        [AC_LANG_SOURCE([[
+#include <math.h>
+volatile double x;
+double y;
+int main ()
+{
+  x = -0.0;
+  y = log10 (x);
+  if (!(y + y == y))
+    return 1;
+  return 0;
+}
+]])],
+        [gl_cv_func_log10_works=yes],
+        [gl_cv_func_log10_works=no],
+        [case "$host_os" in
+           osf*) gl_cv_func_log10_works="guessing no";;
+           *)    gl_cv_func_log10_works="guessing yes";;
+         esac
+        ])
+    ])
 ])