Use GCC5/DWARF5 DW_AT_noreturn to mark functions that don't return normally.

Add a flag field is_noreturn to struct func_type. Make calling_convention
a small bit field to not increase the size of the struct. Set is_noreturn
if the new GCC5/DWARF5 DW_AT_noreturn is set on a DW_TAG_subprogram.
Use this information to warn the user before doing a finish or return from
a function that does not return normally to its caller.

(gdb) finish
warning: Function endless does not return normally.
Try to finish anyway? (y or n)

(gdb) return
warning: Function does not return normally to caller.
Make endless return now? (y or n)

gdb/ChangeLog

	* dwarf2read.c (read_subroutine_type): Set TYPE_NO_RETURN from
	DW_AT_noreturn.
	* gdbtypes.h (struct func_type): Add is_noreturn field flag. Make
	calling_convention an 8 bit bit field.
	(TYPE_NO_RETURN): New macro.
	* infcmd.c (finish_command): Query if function does not return
	normally.
	* stack.c (return_command): Likewise.

gdb/testsuite/ChangeLog

	* gdb.base/noreturn-return.c: New file.
	* gdb.base/noreturn-return.exp: New file.
	* gdb.base/noreturn-finish.c: New file.
	* gdb.base/noreturn-finish.exp: New file.

include/ChangeLog

	* dwarf2.def (DW_AT_noreturn): New DWARF5 attribute.

The dwarf2.h addition and the code to emit the new attribute is already in
the gcc tree.

gdb/ChangeLog

@@ -1,3 +1,14 @@
+2015-01-15  Mark Wielaard  <mjw@redhat.com>
+
+	* dwarf2read.c (read_subroutine_type): Set TYPE_NO_RETURN from
+	DW_AT_noreturn.
+	* gdbtypes.h (struct func_type): Add is_noreturn field flag. Make
+	calling_convention an 8 bit bit field.
+	(TYPE_NO_RETURN): New macro.
+	* infcmd.c (finish_command): Query if function does not return
+	normally.
+	* stack.c (return_command): Likewise.
+
 2015-01-23  Pedro Alves  <palves@redhat.com>
 
 	* linux-nat.c (linux_is_async_p): New macro.

gdb/dwarf2read.c

@@ -14343,6 +14343,12 @@ read_subroutine_type (struct die_info *die, struct dwarf2_cu *cu)
   else
     TYPE_CALLING_CONVENTION (ftype) = DW_CC_normal;
 
+  /* Record whether the function returns normally to its caller or not
+     if the DWARF producer set that information.  */
+  attr = dwarf2_attr (die, DW_AT_noreturn, cu);
+  if (attr && (DW_UNSND (attr) != 0))
+    TYPE_NO_RETURN (ftype) = 1;
+
   /* We need to add the subroutine type to the die immediately so
      we don't infinitely recurse when dealing with parameters
      declared as the same subroutine type.  */

gdb/gdbtypes.h

@@ -1019,9 +1019,16 @@ struct func_type
   {
     /* * The calling convention for targets supporting multiple ABIs.
        Right now this is only fetched from the Dwarf-2
-       DW_AT_calling_convention attribute.  */
+       DW_AT_calling_convention attribute.  The value is one of the
+       DW_CC enum dwarf_calling_convention constants.  */
 
-    unsigned calling_convention;
+    unsigned calling_convention : 8;
+
+    /* * Whether this function normally returns to its caller.  It is
+       set from the DW_AT_noreturn attribute if set on the
+       DW_TAG_subprogram.  */
+
+    unsigned int is_noreturn : 1;
 
     /* * Only those DW_TAG_GNU_call_site's in this function that have
        DW_AT_GNU_tail_call set are linked in this list.  Function
@@ -1245,6 +1252,7 @@ extern void allocate_gnat_aux_type (struct type *);
 #define TYPE_GNAT_SPECIFIC(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.gnat_stuff
 #define TYPE_DESCRIPTIVE_TYPE(thistype) TYPE_GNAT_SPECIFIC(thistype)->descriptive_type
 #define TYPE_CALLING_CONVENTION(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->calling_convention
+#define TYPE_NO_RETURN(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->is_noreturn
 #define TYPE_TAIL_CALL_LIST(thistype) TYPE_MAIN_TYPE(thistype)->type_specific.func_stuff->tail_call_list
 #define TYPE_BASECLASS(thistype,index) TYPE_FIELD_TYPE(thistype, index)
 #define TYPE_N_BASECLASSES(thistype) TYPE_CPLUS_SPECIFIC(thistype)->n_baseclasses

gdb/infcmd.c

@@ -1872,7 +1872,14 @@ finish_command (char *arg, int from_tty)
       if (execution_direction == EXEC_REVERSE)
 	printf_filtered (_("Run back to call of "));
       else
-	printf_filtered (_("Run till exit from "));
+	{
+	  if (function != NULL && TYPE_NO_RETURN (function->type)
+	      && !query (_("warning: Function %s does not return normally.\n"
+			   "Try to finish anyway? "),
+			 SYMBOL_PRINT_NAME (function)))
+	    error (_("Not confirmed."));
+	  printf_filtered (_("Run till exit from "));
+	}
 
       print_stack_frame (get_selected_frame (NULL), 1, LOCATION, 0);
     }

gdb/stack.c

@@ -2462,8 +2462,12 @@ return_command (char *retval_exp, int from_tty)
 	confirmed = query (_("%sMake selected stack frame return now? "),
 			   query_prefix);
       else
-	confirmed = query (_("%sMake %s return now? "), query_prefix,
+	{
-			   SYMBOL_PRINT_NAME (thisfun));
+	  if (TYPE_NO_RETURN (thisfun->type))
+	    warning ("Function does not return normally to caller.");
+	  confirmed = query (_("%sMake %s return now? "), query_prefix,
+			     SYMBOL_PRINT_NAME (thisfun));
+	}
       if (!confirmed)
 	error (_("Not confirmed"));
     }

gdb/testsuite/ChangeLog

@@ -1,3 +1,10 @@
+2015-01-15  Mark Wielaard  <mjw@redhat.com>
+
+	* gdb.base/noreturn-return.c: New file.
+	* gdb.base/noreturn-return.exp: New file.
+	* gdb.base/noreturn-finish.c: New file.
+	* gdb.base/noreturn-finish.exp: New file.
+
 2015-01-23  Pedro Alves  <palves@redhat.com>
 
 	* gdb.threads/continue-pending-after-query.c: New file.

gdb/testsuite/gdb.base/noreturn-finish.c

@@ -0,0 +1,31 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2015 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <stdlib.h>
+
+void __attribute__((noreturn))
+noreturn_func (void)
+{
+  abort ();
+}
+
+int
+main (void)
+{
+  noreturn_func ();
+  return 0;
+}

gdb/testsuite/gdb.base/noreturn-finish.exp

@@ -0,0 +1,51 @@
+# Copyright 2015 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+standard_testfile
+
+if [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} {debug}] {
+    return -1
+}
+
+proc noreturn_finish_test { } {
+    global gdb_prompt
+
+    if { ! [ runto_main ] } then {
+	untested ${testfile}.exp
+	return -1
+    }
+
+    gdb_breakpoint "noreturn_func"
+    gdb_continue_to_breakpoint "noreturn_func"
+
+    set test "cancel finish from noreturn_func"
+    gdb_test_multiple "finish" $test {
+	-re "warning: Function noreturn_func does not return normally" {
+	    verbose -log "saw warning"
+	    exp_continue
+	}
+	-re "Try to finish anyway.*y or n.* $" {
+	    send_gdb "n\n"
+	    exp_continue
+	}
+	-re ".*$gdb_prompt $" {
+	    pass $test
+	}
+   }
+}
+
+clean_restart ${binfile}
+
+noreturn_finish_test

gdb/testsuite/gdb.base/noreturn-return.c

@@ -0,0 +1,31 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2015 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <stdlib.h>
+
+void __attribute__((noreturn))
+noreturn_func (void)
+{
+  abort ();
+}
+
+int
+main (void)
+{
+  noreturn_func ();
+  return 0;
+}

gdb/testsuite/gdb.base/noreturn-return.exp

@@ -0,0 +1,51 @@
+# Copyright 2015 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+standard_testfile
+
+if [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} {debug}] {
+    return -1
+}
+
+proc noreturn_test { } {
+    global gdb_prompt
+
+    if { ! [ runto_main ] } then {
+	untested ${testfile}.exp
+	return -1
+    }
+
+    gdb_breakpoint "noreturn_func"
+    gdb_continue_to_breakpoint "noreturn_func"
+
+    set test "cancel return from noreturn_func"
+    gdb_test_multiple "return" $test {
+	-re "warning: Function does not return normally to caller" {
+	    verbose -log "saw warning"
+	    exp_continue
+	}
+	-re "Make noreturn_func return now.*y or n. $" {
+	    send_gdb "n\n"
+	    exp_continue
+	}
+	-re "Not confirmed.*$gdb_prompt $" {
+	    pass $test
+	}
+   }
+}
+
+clean_restart ${binfile}
+
+noreturn_test

include/ChangeLog

@@ -1,3 +1,7 @@
+2015-01-15  Mark Wielaard  <mjw@redhat.com>
+
+	* dwarf2.def (DW_AT_noreturn): New DWARF5 attribute.
+
 2015-01-14  Jan-Benedict Glaw  <jbglaw@lug-owl.de>
 
 	* libiberty.h: Merge from GCC.

include/dwarf2.def

@@ -306,6 +306,8 @@ DW_AT (DW_AT_data_bit_offset, 0x6b)
 DW_AT (DW_AT_const_expr, 0x6c)
 DW_AT (DW_AT_enum_class, 0x6d)
 DW_AT (DW_AT_linkage_name, 0x6e)
+/* DWARF 5.  */
+DW_AT (DW_AT_noreturn, 0x87)
 
 DW_AT_DUP (DW_AT_lo_user, 0x2000) /* Implementation-defined range start.  */
 DW_AT_DUP (DW_AT_hi_user, 0x3fff) /* Implementation-defined range end.  */