X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=m4%2Ftrunc.m4;h=62311015b75136d401386c80c39d26e8f07cb581;hb=ee595ffa35986a68e78718000cc31cfd971c319c;hp=1d003c3e2e453d94c50702f43e5d3c2839db3c6c;hpb=b2e2010c7c902235b5efb5bd3c6529f61b093aa4;p=gnulib.git

diff --git a/m4/trunc.m4 b/m4/trunc.m4
index 1d003c3e2..62311015b 100644
--- a/m4/trunc.m4
+++ b/m4/trunc.m4
@@ -1,11 +1,12 @@
-# trunc.m4 serial 2
-dnl Copyright (C) 2007, 2009, 2010 Free Software Foundation, Inc.
+# trunc.m4 serial 7
+dnl Copyright (C) 2007, 2010-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN([gl_FUNC_TRUNC],
 [
+  m4_divert_text([DEFAULTS], [gl_trunc_required=plain])
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   dnl Persuade glibc <math.h> to declare trunc().
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
@@ -14,35 +15,74 @@ AC_DEFUN([gl_FUNC_TRUNC],
   if test "$ac_cv_have_decl_trunc" = yes; then
     dnl Test whether trunc() can be used without libm.
     TRUNC_LIBM=?
-    AC_TRY_LINK([
-       #ifndef __NO_MATH_INLINES
-       # define __NO_MATH_INLINES 1 /* for glibc */
-       #endif
-       #include <math.h>
-       double x;],
-      [x = trunc(x);],
+    AC_LINK_IFELSE(
+      [AC_LANG_PROGRAM(
+         [[#ifndef __NO_MATH_INLINES
+           # define __NO_MATH_INLINES 1 /* for glibc */
+           #endif
+           #include <math.h>
+           double x;]],
+         [[x = trunc(x);]])],
       [TRUNC_LIBM=])
     if test "$TRUNC_LIBM" = "?"; then
       save_LIBS="$LIBS"
       LIBS="$LIBS -lm"
-      AC_TRY_LINK([
-         #ifndef __NO_MATH_INLINES
-         # define __NO_MATH_INLINES 1 /* for glibc */
-         #endif
-         #include <math.h>
-         double x;],
-        [x = trunc(x);],
+      AC_LINK_IFELSE(
+        [AC_LANG_PROGRAM(
+           [[#ifndef __NO_MATH_INLINES
+             # define __NO_MATH_INLINES 1 /* for glibc */
+             #endif
+             #include <math.h>
+             double x;]],
+           [[x = trunc(x);]])],
         [TRUNC_LIBM="-lm"])
       LIBS="$save_LIBS"
     fi
     if test "$TRUNC_LIBM" = "?"; then
       TRUNC_LIBM=
     fi
+    m4_ifdef([gl_FUNC_TRUNC_IEEE], [
+      if test $gl_trunc_required = ieee && test $REPLACE_TRUNC = 0; then
+        AC_CACHE_CHECK([whether trunc works according to ISO C 99 with IEC 60559],
+          [gl_cv_func_trunc_ieee],
+          [
+            save_LIBS="$LIBS"
+            LIBS="$LIBS $TRUNC_LIBM"
+            AC_RUN_IFELSE(
+              [AC_LANG_SOURCE([[
+#ifndef __NO_MATH_INLINES
+# define __NO_MATH_INLINES 1 /* for glibc */
+#endif
+#include <math.h>
+]gl_DOUBLE_MINUS_ZERO_CODE[
+]gl_DOUBLE_SIGNBIT_CODE[
+static double dummy (double f) { return 0; }
+int main (int argc, char *argv[])
+{
+  double (*my_trunc) (double) = argc ? trunc : dummy;
+  /* Test whether trunc (-0.0) is -0.0.  */
+  if (signbitd (minus_zerod) && !signbitd (my_trunc (minus_zerod)))
+    return 1;
+  return 0;
+}
+              ]])],
+              [gl_cv_func_trunc_ieee=yes],
+              [gl_cv_func_trunc_ieee=no],
+              [gl_cv_func_trunc_ieee="guessing no"])
+            LIBS="$save_LIBS"
+          ])
+        case "$gl_cv_func_trunc_ieee" in
+          *yes) ;;
+          *) REPLACE_TRUNC=1 ;;
+        esac
+      fi
+    ])
   else
     HAVE_DECL_TRUNC=0
-    AC_LIBOBJ([trunc])
+  fi
+  if test $HAVE_DECL_TRUNC = 0 || test $REPLACE_TRUNC = 1; then
+    dnl No libraries are needed to link lib/trunc.c.
     TRUNC_LIBM=
   fi
-  AC_SUBST([HAVE_DECL_TRUNC])
   AC_SUBST([TRUNC_LIBM])
 ])