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.

1 files changed, 6 insertions, 2 deletions

diff --git a/gdb/stack.c b/gdb/stack.c
index 0201d0a..5f2a3dc 100644
--- a/gdb/stack.c
+++ b/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"));
     }