Hi,

this simple bug led me to rethink normal and error termination and
thus the patch changes some other related stuff as well. So the
original problem was that when -fdump-core was enabled, STOP with a
numeric stop code made the program terminate with an incorrect return
code, since the core dump generation is done by the program killing
itself.

The real problem is that previously, we were mixing up normal
termination with a non-zero exit status (e.g. file not found) with
aborting the program (e.g. some serious error detected). The attached
patch reworks this so that normal termination (with a zero or non-zero
exit code) is done with exit(), and no backtrace or core dump is
generated in any circumstance. For serious errors, a backtrace and
core dump are generated.

Since OS'es contain widely used ways to control core dump generation
(e.g. ulimit -c), and we no longer "frivolously" try to generate a
core dump just because we're exiting with non-zero status, there is
IMHO no longer any need for a gfortran-specific option; if we hit a
serious error, we call abort() and a core dump is always generated if
the user environment is so configured (and the system supports core
dumps).

Also, since backtraces and core dumps are now only generated for
serious errors (not e.g. file not found). -fbacktrace is enabled by
default.

Regtested on x86_64-unknown-linux-gnu, Ok for trunk?

frontend ChangeLog:

2011-05-07  Janne Blomqvist  <jb@gcc.gnu.org>

	PR libfortran/48915
	* gfortran.h (gfc_option_t): Remove flag_dump_core.
	* gfortran.texi (GFORTRAN_ERROR_DUMPCORE): Remove section.
	(GFORTRAN_ERROR_BACKTRACE): Document that it's enabled by default.
	* intrinsic.texi (ABORT): Remove explanation of -fdump-core.
	* invoke.texi: Remove -fdump-core, document that -fbacktrace is
	enabled by default.
	* lang.opt: Remove -fdump-core.
	* options.c (gfc_init_options): Make backtrace default to enabled,
	remove dump_core.
	(gfc_handle_option): Remove OPT_fdump-core.
	* trans-decl.c: Pass a 0 to preserve ABI.

library ChangeLog:

2011-05-07  Janne Blomqvist  <jb@gcc.gnu.org>

	PR libfortran/48915
	* intrinsics/abort.c (abort): Call sys_abort().
	* io/unix.c (st_vprintf): Call sys_abort().
	* libgfortran.h (options_t): Remove dump_core member.
	(handler): Rename to backtrace_handler.
	(compile_options_t): Remove dump_core member.
	(sys_exit): Remove.
	(sys_abort): New function.
	* runtime/backtrace.c (show_backtrace): Print a message if
	backtrace is not available on target.
	* runtime/compile_options.c (backtrace_handler): New
	implementation based on example in Glibc manual.
	(set_options): Remove dump_core handling, make signal handler
	handle more signals.
	(init_compile_options): Remove dump_core.
	* runtime/environ.c (variable_table[]): Remove
	GFORTRAN_ERROR_DUMPCORE element.
	(show_variables): Update name, call exit().
	* runtime/error.c (sys_exit): Remove.
	(sys_abort): New function.
	(recursion_check): Call sys_abort().
	(os_error): Call exit().
	(runtime_error): Likewise.
	(runtime_error_at): Likewise.
	(internal_error): Likewise.
	(generate_error): Likewise.
	(notify_std): Likewise.
	* runtime/stop.c (stop_numeric): Call exit().
	(stop_numeric_f08): Likewise.
	(stop_string): Likewise.
	(error_stop_string): Call sys_abort().
	(error_stop_numeric): Print backtrace, exit with provided code.


-- 
Janne Blomqvist