logf: Work around OSF/1 5.1 bug.

[gnulib.git] / m4 / logf.m4

diff --git a/m4/logf.m4 b/m4/logf.m4
index f4173f0..0e4fa5d 100644 (file)
--- a/m4/logf.m4
+++ b/m4/logf.m4
@@ -1,5 +1,5 @@
-# logf.m4 serial 1
-dnl Copyright (C) 2011 Free Software Foundation, Inc.
+# logf.m4 serial 3
+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,
 dnl with or without modifications, as long as this notice is preserved.
@@ -9,6 +9,9 @@ AC_DEFUN([gl_FUNC_LOGF],
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   AC_REQUIRE([gl_FUNC_LOG])
 
+  dnl Persuade glibc <math.h> to declare logf().
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+
   dnl Test whether logf() exists. Assume that logf(), if it exists, is
   dnl defined in the same library as log().
   save_LIBS="$LIBS"
@@ -17,9 +20,54 @@ AC_DEFUN([gl_FUNC_LOGF],
   LIBS="$save_LIBS"
   if test $ac_cv_func_logf = yes; then
     LOGF_LIBM="$LOG_LIBM"
+    save_LIBS="$LIBS"
+    LIBS="$LIBS $LOGF_LIBM"
+    gl_FUNC_LOGF_WORKS
+    LIBS="$save_LIBS"
+    case "$gl_cv_func_logf_works" in
+      *yes) ;;
+      *) REPLACE_LOGF=1 ;;
+    esac
   else
     HAVE_LOGF=0
-    LOGF_LIBM="$LOG_LIBM"
+  fi
+  if test $HAVE_LOGF = 0 || test $REPLACE_LOGF = 1; then
+    dnl Find libraries needed to link lib/logf.c.
+    if test $HAVE_LOGF = 0; then
+      LOGF_LIBM="$LOG_LIBM"
+    fi
   fi
   AC_SUBST([LOGF_LIBM])
 ])
+
+dnl Test whether logf() works.
+dnl On OSF/1 5.1, logf(-0.0f) is NaN.
+AC_DEFUN([gl_FUNC_LOGF_WORKS],
+[
+  AC_REQUIRE([AC_PROG_CC])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  AC_CACHE_CHECK([whether logf works], [gl_cv_func_logf_works],
+    [
+      AC_RUN_IFELSE(
+        [AC_LANG_SOURCE([[
+#include <math.h>
+volatile float x;
+float y;
+int main ()
+{
+  x = -0.0f;
+  y = logf (x);
+  if (!(y + y == y))
+    return 1;
+  return 0;
+}
+]])],
+        [gl_cv_func_logf_works=yes],
+        [gl_cv_func_logf_works=no],
+        [case "$host_os" in
+           osf*) gl_cv_func_logf_works="guessing no";;
+           *)    gl_cv_func_logf_works="guessing yes";;
+         esac
+        ])
+    ])
+])