2013-06-12  Tobias Burnus  <burnus@net-b.de>

	* gfortran.h (gfc_option_t): Add flag_underflow_warning.
	* gfortran.texi (_gfortran_set_options): Update.
	* invoke.texi (-funderflow-warning): Add doc.
	* lang.opt (fno-underflow-warning): Add flag.
	* options.c (gfc_init_options, gfc_handle_option): Handle it.
	* trans-decl.c (create_main_function): Update
	_gfortran_set_options call.

2013-06-12  Tobias Burnus  <burnus@net-b.de>

	* libgfortran.h (compile_options_t) Add underflow_warning.
	(get_fpu_except_flags): New prototype.
	* runtime/compile_options.c (set_options, init_compile_options):
	Handle underflow_warning.
	* runtime/stop.c (report_exception): New function.
	(stop_numeric, stop_numeric_f08, stop_string, error_stop_string,
	error_stop_numeric): Call it.
	* config/fpu-387.h (get_fpu_except_flags): New function.
	* config/fpu-aix.h (get_fpu_except_flags): New function.
	* config/fpu-generic.h (get_fpu_except_flags): New function.
	* config/fpu-glibc.h (get_fpu_except_flags): New function.
	* config/fpu-glibc.h (get_fpu_except_flags): New function.
	* configure.ac: Check for fpxcp.h.
	* configure: Regenerate.
	* config.h.in: Regenerate.

diff --git a/gcc/fortran/gfortran.h b/gcc/fortran/gfortran.h
index 14da0af..28b47ac 100644
--- a/gcc/fortran/gfortran.h
+++ b/gcc/fortran/gfortran.h
@@ -2299,6 +2299,7 @@ typedef struct
   int flag_align_commons;
   int flag_protect_parens;
   int flag_realloc_lhs;
+  int flag_underflow_warning;
   int flag_aggressive_function_elimination;
   int flag_frontend_optimize;
 
diff --git a/gcc/fortran/gfortran.texi b/gcc/fortran/gfortran.texi
index 4a31a77..d8ed562 100644
--- a/gcc/fortran/gfortran.texi
+++ b/gcc/fortran/gfortran.texi
@@ -2855,13 +2855,16 @@ Default: enabled.
 are (bitwise or-ed): GFC_RTCHECK_BOUNDS (1), GFC_RTCHECK_ARRAY_TEMPS (2),
 GFC_RTCHECK_RECURSION (4), GFC_RTCHECK_DO (16), GFC_RTCHECK_POINTER (32).
 Default: disabled.
+@item @var{option}[7] @tab Unused.
+@item @var{option}[8] @tab Show a warning when invoking @code{STOP} and
+@code{ERROR STOP} if a floating-point underflow occurred.
 @end multitable
 
 @item @emph{Example}:
 @smallexample
-  /* Use gfortran 4.8 default options.  */
-  static int options[] = @{68, 511, 0, 0, 1, 1, 0@};
-  _gfortran_set_options (7, &options);
+  /* Use gfortran 4.9 default options.  */
+  static int options[] = @{68, 511, 0, 0, 1, 1, 0, 0, 1@};
+  _gfortran_set_options (9, &options);
 @end smallexample
 @end table
 
diff --git a/gcc/fortran/invoke.texi b/gcc/fortran/invoke.texi
index 12c200e..63a1ffb 100644
--- a/gcc/fortran/invoke.texi
+++ b/gcc/fortran/invoke.texi
@@ -1157,8 +1157,17 @@ negative in the @code{SIGN} intrinsic.  @option{-fno-sign-zero} does not
 print the negative sign of zero values (or values rounded to zero for I/O)
 and regards zero as positive number in the @code{SIGN} intrinsic for
 compatibility with Fortran 77. The default is @option{-fsign-zero}.
+
+@item -fno-underflow-warning
+@opindex @code{funderflow-warning}
+When @code{STOP} and @code{ERROR STOP} is invoked, a warning is printed to
+@code{ERROR_UNIT} if a floating-point status flag is set (other than inexact).
+When @option{-fno-underflow-warning} is set, no warning is shown if a
+floating-point underflow occurred.  The default is
+@option{-funderflow-warning}.
 @end table
 
+
 @node Code Gen Options
 @section Options for code generation conventions
 @cindex code generation, conventions
diff --git a/gcc/fortran/lang.opt b/gcc/fortran/lang.opt
index dbc3f6b..e0e71b4 100644
--- a/gcc/fortran/lang.opt
+++ b/gcc/fortran/lang.opt
@@ -585,6 +585,10 @@ fshort-enums
 Fortran Var(flag_short_enums)
 ; Documented in C
 
+funderflow-warning
+Fortran
+On run-time exit, show a warning if an underflow occurred
+
 fsign-zero
 Fortran
 Apply negative sign to zero values
diff --git a/gcc/fortran/options.c b/gcc/fortran/options.c
index 3f5de03..34d066d 100644
--- a/gcc/fortran/options.c
+++ b/gcc/fortran/options.c
@@ -157,6 +157,7 @@ gfc_init_options (unsigned int decoded_options_count,
   gfc_option.flag_align_commons = 1;
   gfc_option.flag_protect_parens = -1;
   gfc_option.flag_realloc_lhs = -1;
+  gfc_option.flag_underflow_warning = 1;
   gfc_option.flag_aggressive_function_elimination = 0;
   gfc_option.flag_frontend_optimize = -1;
   
@@ -980,6 +981,10 @@ gfc_handle_option (size_t scode, const char *arg, int value,
       gfc_option.flag_sign_zero = value;
       break;
 
+    case OPT_funderflow_warning:
+      gfc_option.flag_underflow_warning = value;
+      break;
+
     case OPT_ffpe_trap_:
       gfc_handle_fpe_trap_option (arg);
       break;
diff --git a/gcc/fortran/trans-decl.c b/gcc/fortran/trans-decl.c
index 87652ba..06a299f 100644
--- a/gcc/fortran/trans-decl.c
+++ b/gcc/fortran/trans-decl.c
@@ -5171,14 +5239,15 @@ create_main_function (tree fndecl)
     /* TODO: This is the -frange-check option, which no longer affects
        library behavior; when bumping the library ABI this slot can be
        reused for something else. As it is the last element in the
-       array, we can instead leave it out altogether.
+       array, we can instead leave it out altogether. */
+    CONSTRUCTOR_APPEND_ELT (v, NULL_TREE,
+                            build_int_cst (integer_type_node, 0));
     CONSTRUCTOR_APPEND_ELT (v, NULL_TREE,
                             build_int_cst (integer_type_node,
-                                           gfc_option.flag_range_check));
-    */
+                                           gfc_option.flag_underflow_warning));
 
     array_type = build_array_type (integer_type_node,
-				   build_index_type (size_int (6)));
+				   build_index_type (size_int (8)));
     array = build_constructor (array_type, v);
     TREE_CONSTANT (array) = 1;
     TREE_STATIC (array) = 1;
@@ -5193,7 +5262,7 @@ create_main_function (tree fndecl)
 
     tmp = build_call_expr_loc (input_location,
 			   gfor_fndecl_set_options, 2,
-			   build_int_cst (integer_type_node, 7), var);
+			   build_int_cst (integer_type_node, 9), var);
     gfc_add_expr_to_block (&body, tmp);
   }
 
diff --git a/libgfortran/config/fpu-387.h b/libgfortran/config/fpu-387.h
index 913eb60..7492127 100644
--- a/libgfortran/config/fpu-387.h
+++ b/libgfortran/config/fpu-387.h
@@ -134,3 +134,37 @@ void set_fpu (void)
       asm volatile ("%vldmxcsr %0" : : "m" (cw_sse));
     }
 }
+
+
+int
+get_fpu_except_flags (void)
+{
+  int result;
+  unsigned short cw;
+
+  __asm__ ("fnstsw %0" : "=a" (cw));
+
+  if (has_sse())
+    {
+      unsigned int cw_sse;
+      __asm__ ("stmxcsr %0" : "=m" (*&cw_sse));
+      cw |= cw_sse;
+    }
+
+  if (cw & _FPU_MASK_IM)
+    result |= GFC_FPE_INVALID;
+
+  if (cw & _FPU_MASK_ZM)
+    result |= GFC_FPE_ZERO;
+
+  if (cw & _FPU_MASK_OM)
+    result |= GFC_FPE_OVERFLOW;
+
+  if (cw & _FPU_MASK_UM)
+    result |= GFC_FPE_UNDERFLOW;
+
+  if (cw & _FPU_MASK_PM)
+    result |= GFC_FPE_INEXACT;
+
+  return result;
+}
diff --git a/libgfortran/config/fpu-aix.h b/libgfortran/config/fpu-aix.h
index bcb5500..1ba9d4c 100644
--- a/libgfortran/config/fpu-aix.h
+++ b/libgfortran/config/fpu-aix.h
@@ -29,6 +29,10 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #include <fptrap.h>
 #endif
 
+#ifdef HAVE_FPXCP_H
+#include <fpxcp.h>
+#endif
+
 void
 set_fpu (void)
 {
@@ -81,3 +85,34 @@ set_fpu (void)
   fp_trap(FP_TRAP_SYNC);
   fp_enable(mode);
 }
+
+
+int
+get_fpu_except_flags (void)
+{
+  int result, set_excepts;
+
+  result = 0;
+
+#ifdef HAVE_FPXCP_H
+  if (!fp_any_xcp ())
+    return 0;
+
+  if (fp_invalid_op ())
+    result |= GFC_FPE_INVALID;
+
+  if (fp_divbyzero ())
+    result |= GFC_FPE_ZERO;
+
+  if (fp_overflow ())
+    result |= GFC_FPE_OVERFLOW;
+
+  if (fp_underflow ())
+    result |= GFC_FPE_UNDERFLOW;
+
+  if (fp_inexact ())
+    result |= GFC_FPE_INEXACT;
+#endif
+
+  return result;
+}
diff --git a/libgfortran/config/fpu-generic.h b/libgfortran/config/fpu-generic.h
index 23212f8..4223f2e 100644
--- a/libgfortran/config/fpu-generic.h
+++ b/libgfortran/config/fpu-generic.h
@@ -50,3 +50,9 @@ set_fpu (void)
     estr_write ("Fortran runtime warning: IEEE 'inexact' "
 	        "exception not supported.\n");
 }
+
+int
+get_fpu_except_flags (void)
+{
+  return 0;
+}
diff --git a/libgfortran/config/fpu-glibc.h b/libgfortran/config/fpu-glibc.h
index 5c7ad84..b300372 100644
--- a/libgfortran/config/fpu-glibc.h
+++ b/libgfortran/config/fpu-glibc.h
@@ -85,3 +85,40 @@ void set_fpu (void)
 	        "exception not supported.\n");
 #endif
 }
+
+
+int
+get_fpu_except_flags (void)
+{
+  int result, set_excepts;
+
+  result = 0;
+  set_excepts = fetestexcept (FE_ALL_EXCEPT);
+
+#ifdef FE_INVALID
+  if (set_excepts & FE_INVALID)
+    result |= GFC_FPE_INVALID;
+#endif
+
+#ifdef FE_DIVBYZERO
+  if (set_excepts & FE_DIVBYZERO)
+    result |= GFC_FPE_ZERO;
+#endif
+
+#ifdef FE_OVERFLOW
+  if (set_excepts & FE_OVERFLOW)
+    result |= GFC_FPE_OVERFLOW;
+#endif
+
+#ifdef FE_UNDERFLOW
+  if (set_excepts & FE_UNDERFLOW)
+    result |= GFC_FPE_UNDERFLOW;
+#endif
+
+#ifdef FE_INEXACT
+  if (set_excepts & FE_INEXACT)
+    result |= GFC_FPE_INEXACT;
+#endif
+
+  return result;
+}
diff --git a/libgfortran/config/fpu-sysv.h b/libgfortran/config/fpu-sysv.h
index b32702b..160c4b5 100644
--- a/libgfortran/config/fpu-sysv.h
+++ b/libgfortran/config/fpu-sysv.h
@@ -80,3 +80,40 @@ set_fpu (void)
 
   fpsetmask(cw);
 }
+
+int
+get_fpu_except_flags (void)
+{
+  int result;
+  fp_except_t set_excepts;
+
+  result = 0;
+  set_excepts = fpgetsticky ();
+
+#ifdef FP_X_INV
+  if (set_excepts & FP_X_INV)
+    result |= GFC_FPE_INVALID;
+#endif
+
+#ifdef FP_X_DZ
+  if (set_excepts & FP_X_DZ)
+    result |= GFC_FPE_ZERO;
+#endif
+
+#ifdef FP_X_OFL
+  if (set_excepts & FP_X_OFL)
+    result |= GFC_FPE_OVERFLOW;
+#endif
+
+#ifdef FP_X_UFL
+  if (set_excepts & FP_X_UFL)
+    result |= GFC_FPE_UNDERFLOW;
+#endif
+
+#ifdef FP_X_IMP
+  if (set_excepts & FP_X_IMP)
+    result |= GFC_FPE_INEXACT;
+#endif
+
+  return result;
+}
diff --git a/libgfortran/configure.ac b/libgfortran/configure.ac
index 7d97fed..ba14f1f 100644
--- a/libgfortran/configure.ac
+++ b/libgfortran/configure.ac
@@ -254,7 +254,7 @@ AC_CHECK_TYPES([ptrdiff_t])
 # check header files (we assume C89 is available, so don't check for that)
 AC_CHECK_HEADERS_ONCE(unistd.h sys/time.h sys/times.h sys/resource.h \
 sys/types.h sys/stat.h sys/wait.h floatingpoint.h ieeefp.h fenv.h fptrap.h \
-pwd.h complex.h) 
+fpxcp.h pwd.h complex.h) 
 
 GCC_HEADER_STDINT(gstdint.h)
 
diff --git a/libgfortran/libgfortran.h b/libgfortran/libgfortran.h
index 56c9871..cc759ac 100644
--- a/libgfortran/libgfortran.h
+++ b/libgfortran/libgfortran.h
@@ -534,6 +534,7 @@ typedef struct
   size_t record_marker;
   int max_subrecord_length;
   int bounds_check;
+  int underflow_warning;
 }
 compile_options_t;
 
@@ -742,6 +743,8 @@ internal_proto(gf_strerror);
 
 extern void set_fpu (void);
 internal_proto(set_fpu);
+extern int get_fpu_except_flags (void);
+internal_proto(get_fpu_except_flags);
 
 /* memory.c */
 
diff --git a/libgfortran/runtime/compile_options.c b/libgfortran/runtime/compile_options.c
index a49514c..8246606 100644
--- a/libgfortran/runtime/compile_options.c
+++ b/libgfortran/runtime/compile_options.c
@@ -173,6 +173,8 @@ set_options (int num, int options[])
      the library behavior; range checking is now always done when
      parsing integers. It's place in the options array is retained due
      to ABI compatibility. Remove when bumping the library ABI.  */
+  if (num >= 9)
+    compile_options.underflow_warning = options[8];
 
   /* If backtrace is required, we set signal handlers on the POSIX
      2001 signals with core action.  */
@@ -225,6 +227,7 @@ init_compile_options (void)
   compile_options.pedantic = 0;
   compile_options.backtrace = 0;
   compile_options.sign_zero = 1;
+  compile_options.underflow_warning = 1;
 }
 
 /* Function called by the front-end to tell us the
diff --git a/libgfortran/runtime/stop.c b/libgfortran/runtime/stop.c
index 4805412..00cd717 100644
--- a/libgfortran/runtime/stop.c
+++ b/libgfortran/runtime/stop.c
@@ -32,6 +32,37 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #endif
 
 
+/* Fortran 2008 demands: If any exception (14) is signaling on that image, the
+   processor shall issue a warning indicating which exceptions are signaling;
+   this warning shall be on the unit identified by the named constant
+   ERROR_UNIT (13.8.2.8).  In line with other compilers, we do not report
+   inexact - and we optionally ignore underflow, cf. thread starting at
+   http://mailman.j3-fortran.org/pipermail/j3/2013-June/006452.html.  */
+
+static void
+report_exception (void)
+{
+  int set_excepts = get_fpu_except_flags ();
+  if (!set_excepts)
+    return;
+
+  estr_write ("Note: The following floating-point status flag is signalling:");
+
+  if (set_excepts & GFC_FPE_INVALID)
+    estr_write (" IEEE INVALID FLAG");
+  if (set_excepts & GFC_FPE_ZERO)
+    estr_write (" IEEE_DIVIDE_BY_ZERO");
+  if (set_excepts & GFC_FPE_OVERFLOW)
+    estr_write (" IEEE_OVERFLOW_FLAG");
+  if (compile_options.underflow_warning && (set_excepts & GFC_FPE_UNDERFLOW))
+    estr_write (" IEEE_UNDERFLOW_FLAG");
+  /*  if (set_excepts & GFC_FPE_INEXACT)
+    estr_write (" IEEE_INEXACT_FLAG");  */
+
+  estr_write ("\n");
+}
+
+
 /* A numeric STOP statement.  */
 
 extern void stop_numeric (GFC_INTEGER_4)
@@ -41,6 +72,7 @@ export_proto(stop_numeric);
 void
 stop_numeric (GFC_INTEGER_4 code)
 {
+  report_exception ();
   if (code == -1)
     code = 0;
   else
@@ -59,6 +91,7 @@ export_proto(stop_numeric_f08);
 void
 stop_numeric_f08 (GFC_INTEGER_4 code)
 {
+  report_exception ();
   st_printf ("STOP %d\n", (int)code);
   exit (code);
 }
@@ -69,6 +102,7 @@ stop_numeric_f08 (GFC_INTEGER_4 code)
 void
 stop_string (const char *string, GFC_INTEGER_4 len)
 {
+  report_exception ();
   if (string)
     {
       estr_write ("STOP ");
@@ -91,6 +125,7 @@ export_proto(error_stop_string);
 void
 error_stop_string (const char *string, GFC_INTEGER_4 len)
 {
+  report_exception ();
   estr_write ("ERROR STOP ");
   (void) write (STDERR_FILENO, string, len);
   estr_write ("\n");
@@ -108,6 +143,7 @@ export_proto(error_stop_numeric);
 void
 error_stop_numeric (GFC_INTEGER_4 code)
 {
+  report_exception ();
   st_printf ("ERROR STOP %d\n", (int) code);
   exit (code);
 }
diff --git a/libgfortran/config.h.in b/libgfortran/config.h.in
index fb5026f..0d5d56c 100644
--- a/libgfortran/config.h.in
+++ b/libgfortran/config.h.in
@@ -399,6 +399,9 @@
 /* Define to 1 if you have the <fptrap.h> header file. */
 #undef HAVE_FPTRAP_H
 
+/* Define to 1 if you have the <fpxcp.h> header file. */
+#undef HAVE_FPXCP_H
+
 /* fp_enable is present */
 #undef HAVE_FP_ENABLE

diff --git a/libgfortran/configure b/libgfortran/configure
index 8601d84..c049cdc 100755
--- a/libgfortran/configure
+++ b/libgfortran/configure
@@ -654,7 +654,6 @@ CPP
 am__fastdepCC_FALSE
 am__fastdepCC_TRUE
 CCDEPMODE
-am__nodep
 AMDEPBACKSLASH
 AMDEP_FALSE
 AMDEP_TRUE
@@ -2543,6 +2542,7 @@ as_fn_append ac_header_list " floatingpoint.h"
 as_fn_append ac_header_list " ieeefp.h"
 as_fn_append ac_header_list " fenv.h"
 as_fn_append ac_header_list " fptrap.h"
+as_fn_append ac_header_list " fpxcp.h"
 as_fn_append ac_header_list " pwd.h"
 as_fn_append ac_header_list " complex.h"
 as_fn_append ac_func_list " getrusage"
@@ -3386,11 +3386,11 @@ MAKEINFO=${MAKEINFO-"${am_missing_run}makeinfo"}
 
 # We need awk for the "check" target.  The system "awk" is bad on
 # some platforms.
-# Always define AMTAR for backward compatibility.  Yes, it's still used
-# in the wild :-(  We should find a proper way to deprecate it ...
-AMTAR='$${TAR-tar}'
+# Always define AMTAR for backward compatibility.
 
-am__tar='$${TAR-tar} chof - "$$tardir"' am__untar='$${TAR-tar} xf -'
+AMTAR=${AMTAR-"${am_missing_run}tar"}
+
+am__tar='${AMTAR} chof - "$$tardir"'; am__untar='${AMTAR} xf -'
 
 
 
@@ -3523,7 +3523,6 @@ fi
 if test "x$enable_dependency_tracking" != xno; then
   am_depcomp="$ac_aux_dir/depcomp"
   AMDEPBACKSLASH='\'
-  am__nodep='_no'
 fi
  if test "x$enable_dependency_tracking" != xno; then
   AMDEP_TRUE=
@@ -4341,7 +4340,6 @@ else
   # instance it was reported that on HP-UX the gcc test will end up
   # making a dummy file named `D' -- because `-MD' means `put the output
   # in D'.
-  rm -rf conftest.dir
   mkdir conftest.dir
   # Copy depcomp to subdir because otherwise we won't find it if we're
   # using a relative directory.
@@ -4401,7 +4399,7 @@ else
 	break
       fi
       ;;
-    msvc7 | msvc7msys | msvisualcpp | msvcmsys)
+    msvisualcpp | msvcmsys)
       # This compiler won't grok `-c -o', but also, the minuso test has
       # not run yet.  These depmodes are late enough in the game, and
       # so weak that their functioning should not be impacted.
@@ -5517,7 +5515,6 @@ else
   # instance it was reported that on HP-UX the gcc test will end up
   # making a dummy file named `D' -- because `-MD' means `put the output
   # in D'.
-  rm -rf conftest.dir
   mkdir conftest.dir
   # Copy depcomp to subdir because otherwise we won't find it if we're
   # using a relative directory.
@@ -5577,7 +5574,7 @@ else
 	break
       fi
       ;;
-    msvc7 | msvc7msys | msvisualcpp | msvcmsys)
+    msvisualcpp | msvcmsys)
       # This compiler won't grok `-c -o', but also, the minuso test has
       # not run yet.  These depmodes are late enough in the game, and
       # so weak that their functioning should not be impacted.
@@ -12334,7 +12331,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 12337 "configure"
+#line 12334 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -12440,7 +12437,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 12443 "configure"
+#line 12440 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -16001,6 +15998,8 @@ done
 
 
 
+
+
 inttype_headers=`echo inttypes.h sys/inttypes.h  | sed -e 's/,/ /g'`
 
 acx_cv_header_stdint=stddef.h
