frexpf: Work around problems on IRIX and mingw.

[gnulib.git] / m4 / frexpf.m4

diff --git a/m4/frexpf.m4 b/m4/frexpf.m4
index 3aa648b..d8f58cd 100644 (file)
--- a/m4/frexpf.m4
+++ b/m4/frexpf.m4
@@ -1,4 +1,4 @@
-# frexpf.m4 serial 2
+# frexpf.m4 serial 3
 dnl Copyright (C) 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,
@@ -13,10 +13,81 @@ AC_DEFUN([gl_FUNC_FREXPF],
   dnl exists, is defined in the same library as frexp(). This is not the case
   dnl on NetBSD, OpenBSD.
   gl_MATHFUNC([frexpf], [float], [(float, int *)])
-  if test $gl_cv_func_frexpf_no_libm = no \
-     && test $gl_cv_func_frexpf_in_libm = no; then
+  if test $gl_cv_func_frexpf_no_libm = yes \
+     || test $gl_cv_func_frexpf_in_libm = yes; then
+    save_LIBS="$LIBS"
+    LIBS="$LIBS $FREXPF_LIBM"
+    gl_FUNC_FREXPF_WORKS
+    LIBS="$save_LIBS"
+    case "$gl_cv_func_frexpf_works" in
+      *yes) ;;
+      *)    REPLACE_FREXPF=1 ;;
+    esac
+  else
     HAVE_FREXPF=0
+  fi
+  if test $HAVE_FREXPF = 0 || test $REPLACE_FREXPF = 1; then
     FREXPF_LIBM="$FREXP_LIBM"
   fi
   AC_SUBST([FREXPF_LIBM])
 ])
+
+dnl Test whether frexpf() works also on infinite numbers (this fails e.g. on
+dnl IRIX 6.5 and mingw) and on negative zero (this fails e.g. on mingw).
+AC_DEFUN([gl_FUNC_FREXPF_WORKS],
+[
+  AC_REQUIRE([AC_PROG_CC])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  AC_CACHE_CHECK([whether frexpf works], [gl_cv_func_frexpf_works],
+    [
+      AC_RUN_IFELSE(
+        [AC_LANG_SOURCE([[
+#include <float.h>
+#include <math.h>
+#include <string.h>
+/* HP cc on HP-UX 10.20 has a bug with the constant expression -0.0.
+   ICC 10.0 has a bug when optimizing the expression -zero.
+   The expression -FLT_MIN * FLT_MIN does not work when cross-compiling
+   to PowerPC on MacOS X 10.5.  */
+#if defined __hpux || defined __sgi || defined __ICC
+static float
+compute_minus_zero (void)
+{
+  return -FLT_MIN * FLT_MIN;
+}
+# define minus_zero compute_minus_zero ()
+#else
+float minus_zero = -0.0f;
+#endif
+int main()
+{
+  int result = 0;
+  volatile float x;
+  float zero = 0.0f;
+  /* Test on infinite numbers.  */
+  x = 1.0f / zero;
+  {
+    int exp;
+    float y = frexpf (x, &exp);
+    if (y != x)
+      result |= 1;
+  }
+  /* Test on negative zero.  */
+  x = minus_zero;
+  {
+    int exp;
+    float y = frexpf (x, &exp);
+    if (memcmp (&y, &x, sizeof x))
+      result |= 2;
+  }
+  return result;
+}]])],
+        [gl_cv_func_frexpf_works=yes],
+        [gl_cv_func_frexpf_works=no],
+        [case "$host_os" in
+           irix* | mingw*) gl_cv_func_frexpf_works="guessing no";;
+           *)              gl_cv_func_frexpf_works="guessing yes";;
+         esac
+        ])
+    ])
+])