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Re: [rfa] catch_exceptions()
- To: Andrew Cagney <ac131313 at cygnus dot com>
- Subject: Re: [rfa] catch_exceptions()
- From: Elena Zannoni <ezannoni at cygnus dot com>
- Date: Thu, 6 Sep 2001 10:52:20 -0400
- Cc: gdb-patches at sources dot redhat dot com
- References: <3B7B1A0E.7040900@cygnus.com>
Andrew Cagney writes:
> Hello,
>
> Following up on my last e-mail, here is a tested patch that adds
> catch_exceptions() to top.c
>
> If this is approved, I think I'll add catch_errors() to the ARI (under
> warnings).
>
> Andrew
Sure, approved. (there is a typo in a comment, see below).
Thanks
Elena
> 2001-08-13 Andrew Cagney <ac131313@redhat.com>
>
> * defs.h (enum return_reason): Renumber so that all values are
> negative.
> (RETURN_MASK): Negate reason.
> (catch_exception_ftype): Declare.
> (catch_exceptions): Declare.
> * top.c (catcher): New function, based on catch_errors. Add in
> parameter func_uiout and out parameters func_val, func_caught and
> func_cleanup. Change type of func to catch_exceptions_ftype.
> Save/restore uiout.
> (struct catch_errors_args): Define.
> (do_catch_errors): New function.
> (catch_errors): Rewrite, use do_catch_errors and catcher.
> (catch_exceptions): New function, use catcher.
>
> Index: defs.h
> ===================================================================
> RCS file: /cvs/src/src/gdb/defs.h,v
> retrieving revision 1.62
> diff -p -r1.62 defs.h
> *** defs.h 2001/08/02 20:57:19 1.62
> --- defs.h 2001/08/15 17:49:33
> *************** extern NORETURN void internal_error (con
> *** 1084,1104 ****
>
> extern NORETURN void nomem (long) ATTR_NORETURN;
>
> ! /* Reasons for calling return_to_top_level. Note: enum value 0 is
> ! reserved for internal use as the return value from an initial
> ! setjmp(). */
>
> enum return_reason
> {
> /* User interrupt. */
> ! RETURN_QUIT = 1,
> /* Any other error. */
> RETURN_ERROR
> };
>
> #define ALL_CLEANUPS ((struct cleanup *)0)
>
> ! #define RETURN_MASK(reason) (1 << (int)(reason))
> #define RETURN_MASK_QUIT RETURN_MASK (RETURN_QUIT)
> #define RETURN_MASK_ERROR RETURN_MASK (RETURN_ERROR)
> #define RETURN_MASK_ALL (RETURN_MASK_QUIT | RETURN_MASK_ERROR)
> --- 1084,1106 ----
>
> extern NORETURN void nomem (long) ATTR_NORETURN;
>
> ! /* Reasons for calling return_to_top_level. NOTE: all reason values
> ! must be less than zero. enum value 0 is reserved for internal use
> ! as the return value from an initial setjmp(). The functioin
^^^^^^^^^
> ! catch_exceptions() reserves values >= 0 as legal results from its
> ! wrapped function. */
>
> enum return_reason
> {
> /* User interrupt. */
> ! RETURN_QUIT = -2,
> /* Any other error. */
> RETURN_ERROR
> };
>
> #define ALL_CLEANUPS ((struct cleanup *)0)
>
> ! #define RETURN_MASK(reason) (1 << (int)(-reason))
> #define RETURN_MASK_QUIT RETURN_MASK (RETURN_QUIT)
> #define RETURN_MASK_ERROR RETURN_MASK (RETURN_ERROR)
> #define RETURN_MASK_ALL (RETURN_MASK_QUIT | RETURN_MASK_ERROR)
> *************** typedef int return_mask;
> *** 1106,1117 ****
>
> extern NORETURN void return_to_top_level (enum return_reason) ATTR_NORETURN;
>
> /* If CATCH_ERRORS_FTYPE throws an error, catch_errors() returns zero
> otherwize the result from CATCH_ERRORS_FTYPE is returned. It is
> probably useful for CATCH_ERRORS_FTYPE to always return a non-zero
> value. It's unfortunate that, catch_errors() does not return an
> indication of the exact exception that it caught - quit_flag might
> ! help. */
>
> typedef int (catch_errors_ftype) (PTR);
> extern int catch_errors (catch_errors_ftype *, PTR, char *, return_mask);
> --- 1108,1148 ----
>
> extern NORETURN void return_to_top_level (enum return_reason) ATTR_NORETURN;
>
> + /* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
> + handler. If an exception (enum return_reason) is thrown using
> + return_to_top_level() than all cleanups installed since
> + catch_exceptions() was entered are invoked, the (-ve) exception
> + value is then returned by catch_exceptions. If FUNC() returns
> + normally (with a postive or zero return value) then that value is
> + returned by catch_exceptions(). It is an internal_error() for
> + FUNC() to return a negative value.
> +
> + For the period of the FUNC() call: UIOUT is installed as the output
> + builder; ERRSTRING is installed as the error/quit message; and a
> + new cleanup_chain is established. The old values are restored
> + before catch_exceptions() returns.
> +
> + FIXME; cagney/2001-08-13: The need to override the global UIOUT
> + builder variable should just go away.
> +
> + This function superseeds catch_errors().
> +
> + This function uses SETJMP() and LONGJUMP(). */
> +
> + struct ui_out;
> + typedef int (catch_exceptions_ftype) (struct ui_out *ui_out, void *args);
> + extern int catch_exceptions (struct ui_out *uiout,
> + catch_exceptions_ftype *func, void *func_args,
> + char *errstring, return_mask mask);
> +
> /* If CATCH_ERRORS_FTYPE throws an error, catch_errors() returns zero
> otherwize the result from CATCH_ERRORS_FTYPE is returned. It is
> probably useful for CATCH_ERRORS_FTYPE to always return a non-zero
> value. It's unfortunate that, catch_errors() does not return an
> indication of the exact exception that it caught - quit_flag might
> ! help.
> !
> ! This function is superseeded by catch_exceptions(). */
>
> typedef int (catch_errors_ftype) (PTR);
> extern int catch_errors (catch_errors_ftype *, PTR, char *, return_mask);
> Index: top.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/top.c,v
> retrieving revision 1.42
> diff -p -r1.42 top.c
> *** top.c 2001/08/01 18:39:23 1.42
> --- top.c 2001/08/15 17:49:40
> ***************
> *** 41,46 ****
> --- 41,47 ----
> #include "version.h"
> #include "serial.h"
> #include "doublest.h"
> + #include "gdb_assert.h"
>
> /* readline include files */
> #include <readline/readline.h>
> *************** return_to_top_level (enum return_reason
> *** 347,356 ****
> (NORETURN void) SIGLONGJMP (*catch_return, (int) reason);
> }
>
> ! /* Call FUNC with arg ARGS, catching any errors. If there is no
> ! error, return the value returned by FUNC. If there is an error,
> ! print ERRSTRING, print the specific error message, then return
> ! zero.
>
> Must not be called with immediate_quit in effect (bad things might
> happen, say we got a signal in the middle of a memcpy to quit_return).
> --- 348,358 ----
> (NORETURN void) SIGLONGJMP (*catch_return, (int) reason);
> }
>
> ! /* Call FUNC() with args FUNC_UIOUT and FUNC_ARGS, catching any
> ! errors. Set FUNC_CAUGHT to an ``enum return_reason'' if the
> ! function is aborted (using return_to_top_level() or zero if the
> ! function returns normally. Set FUNC_VAL to the value returned by
> ! the function or 0 if the function was aborted.
>
> Must not be called with immediate_quit in effect (bad things might
> happen, say we got a signal in the middle of a memcpy to quit_return).
> *************** return_to_top_level (enum return_reason
> *** 378,398 ****
> be consolidated into a single file instead of being distributed
> between utils.c and top.c? */
>
> ! int
> ! catch_errors (catch_errors_ftype *func, void * args, char *errstring,
> ! return_mask mask)
> {
> SIGJMP_BUF *saved_catch;
> SIGJMP_BUF catch;
> - int val;
> struct cleanup *saved_cleanup_chain;
> char *saved_error_pre_print;
> char *saved_quit_pre_print;
>
> /* Return value from SIGSETJMP(): enum return_reason if error or
> quit caught, 0 otherwise. */
> int caught;
>
> /* Override error/quit messages during FUNC. */
>
> saved_error_pre_print = error_pre_print;
> --- 380,409 ----
> be consolidated into a single file instead of being distributed
> between utils.c and top.c? */
>
> ! static void
> ! catcher (catch_exceptions_ftype *func,
> ! struct ui_out *func_uiout,
> ! void *func_args,
> ! int *func_val,
> ! enum return_reason *func_caught,
> ! char *errstring,
> ! return_mask mask)
> {
> SIGJMP_BUF *saved_catch;
> SIGJMP_BUF catch;
> struct cleanup *saved_cleanup_chain;
> char *saved_error_pre_print;
> char *saved_quit_pre_print;
> + struct ui_out *saved_uiout;
>
> /* Return value from SIGSETJMP(): enum return_reason if error or
> quit caught, 0 otherwise. */
> int caught;
>
> + /* Return value from FUNC(): Hopefully non-zero. Explicitly set to
> + zero if an error quit was caught. */
> + int val;
> +
> /* Override error/quit messages during FUNC. */
>
> saved_error_pre_print = error_pre_print;
> *************** catch_errors (catch_errors_ftype *func,
> *** 403,408 ****
> --- 414,424 ----
> if (mask & RETURN_MASK_QUIT)
> quit_pre_print = errstring;
>
> + /* Override the global ``struct ui_out'' builder. */
> +
> + saved_uiout = uiout;
> + uiout = func_uiout;
> +
> /* Prevent error/quit during FUNC from calling cleanups established
> prior to here. */
>
> *************** catch_errors (catch_errors_ftype *func,
> *** 414,420 ****
> catch_return = &catch;
> caught = SIGSETJMP (catch);
> if (!caught)
> ! val = (*func) (args);
> else
> val = 0;
> catch_return = saved_catch;
> --- 430,436 ----
> catch_return = &catch;
> caught = SIGSETJMP (catch);
> if (!caught)
> ! val = (*func) (func_uiout, func_args);
> else
> val = 0;
> catch_return = saved_catch;
> *************** catch_errors (catch_errors_ftype *func,
> *** 426,472 ****
> do_cleanups call (to cover the problem) or an assertion check to
> detect bad FUNCs code. */
>
> ! /* Restore the cleanup chain and error/quit messages to their
> ! original states. */
>
> restore_cleanups (saved_cleanup_chain);
>
> if (mask & RETURN_MASK_QUIT)
> quit_pre_print = saved_quit_pre_print;
> if (mask & RETURN_MASK_ERROR)
> error_pre_print = saved_error_pre_print;
> -
> - /* Return normally if no error/quit event occurred. */
>
> ! if (!caught)
> ! return val;
>
> ! /* If the caller didn't request that the event be caught, relay the
> event to the next containing catch_errors(). */
>
> ! if (!(mask & RETURN_MASK (caught)))
> ! return_to_top_level (caught);
> !
> ! /* Tell the caller that an event was caught.
> !
> ! FIXME: nsd/2000-02-22: When MASK is RETURN_MASK_ALL, the caller
> ! can't tell what type of event occurred.
>
> ! A possible fix is to add a new interface, catch_event(), that
> ! returns enum return_reason after catching an error or a quit.
>
> ! When returning normally, i.e. without catching an error or a
> ! quit, catch_event() could return RETURN_NORMAL, which would be
> ! added to enum return_reason. FUNC would return information
> ! exclusively via ARGS.
>
> ! Alternatively, normal catch_event() could return FUNC's return
> ! value. The caller would need to be aware of potential overlap
> ! with enum return_reason, which could be publicly restricted to
> ! negative values to simplify return value processing in FUNC and
> ! in the caller. */
>
> ! return 0;
> }
>
> struct captured_command_args
> --- 442,519 ----
> do_cleanups call (to cover the problem) or an assertion check to
> detect bad FUNCs code. */
>
> ! /* Restore the cleanup chain, the error/quit messages, and the uiout
> ! builder, to their original states. */
>
> restore_cleanups (saved_cleanup_chain);
>
> + uiout = saved_uiout;
> +
> if (mask & RETURN_MASK_QUIT)
> quit_pre_print = saved_quit_pre_print;
> if (mask & RETURN_MASK_ERROR)
> error_pre_print = saved_error_pre_print;
>
> ! /* Return normally if no error/quit event occurred or this catcher
> ! can handle this exception. The caller analyses the func return
> ! values. */
> !
> ! if (!caught || (mask & RETURN_MASK (caught)))
> ! {
> ! *func_val = val;
> ! *func_caught = caught;
> ! return;
> ! }
>
> ! /* The caller didn't request that the event be caught, relay the
> event to the next containing catch_errors(). */
>
> ! return_to_top_level (caught);
> ! }
>
> ! int
> ! catch_exceptions (struct ui_out *uiout,
> ! catch_exceptions_ftype *func,
> ! void *func_args,
> ! char *errstring,
> ! return_mask mask)
> ! {
> ! int val;
> ! enum return_reason caught;
> ! catcher (func, uiout, func_args, &val, &caught, errstring, mask);
> ! gdb_assert (val >= 0);
> ! gdb_assert (caught <= 0);
> ! if (caught < 0)
> ! return caught;
> ! return val;
> ! }
>
> ! struct catch_errors_args
> ! {
> ! catch_errors_ftype *func;
> ! void *func_args;
> ! };
>
> ! int
> ! do_catch_errors (struct ui_out *uiout, void *data)
> ! {
> ! struct catch_errors_args *args = data;
> ! return args->func (args->func_args);
> ! }
>
> ! int
> ! catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
> ! return_mask mask)
> ! {
> ! int val;
> ! enum return_reason caught;
> ! struct catch_errors_args args;
> ! args.func = func;
> ! args.func_args = func_args;
> ! catcher (do_catch_errors, uiout, &args, &val, &caught, errstring, mask);
> ! if (caught != 0)
> ! return 0;
> ! return val;
> }
>
> struct captured_command_args