[v2,14/22] Simplify exception handling
Commit Message
Now that cleanups have been removed, TRY/CATCH can't be SJLJ-based any
more. This patch simplifies the exception handling code, by removing
the non-working variants.
Note that the "pure" C++ exception handling code is removed as well; I
think the route forward must be to change exceptions to be
self-destructing, so that try_scope_depth can simply be removed.
Some longjmp-based code remains, as it is needed to throw an exception
through readline.
gdb/ChangeLog
2019-02-27 Tom Tromey <tom@tromey.com>
* common/common-exceptions.h (GDB_XCPT_SJMP, GDB_XCPT_TRY)
(GDB_XCPT_RAW_TRY, GDB_XCPT): Remove.
(TRY, CATCH, END_CATCH): Remove some definitions.
* common/common-exceptions.c: Don't use GDB_XCPT.
(catcher_list_size): Remove.
(throw_exception, throw_it): Simplify.
---
gdb/ChangeLog | 9 +++++++
gdb/common/common-exceptions.c | 36 --------------------------
gdb/common/common-exceptions.h | 46 +---------------------------------
3 files changed, 10 insertions(+), 81 deletions(-)
Comments
On 02/27/2019 08:18 PM, Tom Tromey wrote:
> Now that cleanups have been removed, TRY/CATCH can't be SJLJ-based any
> more. This patch simplifies the exception handling code, by removing
> the non-working variants.
>
> Note that the "pure" C++ exception handling code is removed as well;
That's fine, if we're getting rid of TRY/CATCH.
That mode is/was useful to catch issues like these:
https://sourceware.org/ml/gdb-patches/2017-10/msg00080.html
but if we're getting rid of TRY/CATCH, then it won't be
needed anymore, of course.
> I
> think the route forward must be to change exceptions to be
> self-destructing, so that try_scope_depth can simply be removed.
Agreed.
>
> Some longjmp-based code remains, as it is needed to throw an exception
> through readline.
>
> gdb/ChangeLog
> 2019-02-27 Tom Tromey <tom@tromey.com>
>
> * common/common-exceptions.h (GDB_XCPT_SJMP, GDB_XCPT_TRY)
> (GDB_XCPT_RAW_TRY, GDB_XCPT): Remove.
> (TRY, CATCH, END_CATCH): Remove some definitions.
> * common/common-exceptions.c: Don't use GDB_XCPT.
> (catcher_list_size): Remove.
> (throw_exception, throw_it): Simplify.
Looks fine. I spotted a few comments that need updating,
even after the whole series is in, but no need to stress about it.
It's fine to tackle it with a final pass after the series.
I have comments for the other patches, will send them as soon
as possible.
Thanks,
Pedro Alves
@@ -54,26 +54,6 @@ struct catcher
/* Where to go for throw_exception(). */
static struct catcher *current_catcher;
-#if GDB_XCPT == GDB_XCPT_SJMP
-
-/* Return length of current_catcher list. */
-
-static int
-catcher_list_size (void)
-{
- int size;
- struct catcher *catcher;
-
- for (size = 0, catcher = current_catcher;
- catcher != NULL;
- catcher = catcher->prev)
- ++size;
-
- return size;
-}
-
-#endif
-
jmp_buf *
exceptions_state_mc_init (void)
{
@@ -205,8 +185,6 @@ exceptions_state_mc_action_iter_1 (void)
return exceptions_state_mc (CATCH_ITER_1);
}
-#if GDB_XCPT != GDB_XCPT_SJMP
-
/* How many nested TRY blocks we have. See exception_messages and
throw_it. */
@@ -248,8 +226,6 @@ gdb_exception_sliced_copy (struct gdb_exception *to, const struct gdb_exception
*to = *from;
}
-#endif /* !GDB_XCPT_SJMP */
-
/* Return EXCEPTION to the nearest containing CATCH_SJLJ block. */
void
@@ -263,8 +239,6 @@ throw_exception_sjlj (struct gdb_exception exception)
longjmp (current_catcher->buf, exception.reason);
}
-#if GDB_XCPT != GDB_XCPT_SJMP
-
/* Implementation of throw_exception that uses C++ try/catch. */
static ATTRIBUTE_NORETURN void
@@ -288,16 +262,10 @@ throw_exception_cxx (struct gdb_exception exception)
gdb_assert_not_reached ("invalid return reason");
}
-#endif
-
void
throw_exception (struct gdb_exception exception)
{
-#if GDB_XCPT == GDB_XCPT_SJMP
- throw_exception_sjlj (exception);
-#else
throw_exception_cxx (exception);
-#endif
}
/* A stack of exception messages.
@@ -321,11 +289,7 @@ throw_it (enum return_reason reason, enum errors error, const char *fmt,
{
struct gdb_exception e;
char *new_message;
-#if GDB_XCPT == GDB_XCPT_SJMP
- int depth = catcher_list_size ();
-#else
int depth = try_scope_depth;
-#endif
gdb_assert (depth > 0);
@@ -115,22 +115,6 @@ struct gdb_exception
const char *message;
};
-/* The different exception mechanisms that TRY/CATCH can map to. */
-
-/* Make GDB exceptions use setjmp/longjmp behind the scenes. */
-#define GDB_XCPT_SJMP 1
-
-/* Make GDB exceptions use try/catch behind the scenes. */
-#define GDB_XCPT_TRY 2
-
-/* Specify this mode to build with TRY/CATCH mapped directly to raw
- try/catch. GDB won't work correctly, but building that way catches
- code tryin to break/continue out of the try block, along with
- spurious code between the TRY and the CATCH block. */
-#define GDB_XCPT_RAW_TRY 3
-
-#define GDB_XCPT GDB_XCPT_TRY
-
/* Functions to drive the sjlj-based exceptions state machine. Though
declared here by necessity, these functions should be considered
internal to the exceptions subsystem and not used other than via
@@ -141,13 +125,11 @@ extern int exceptions_state_mc_action_iter (void);
extern int exceptions_state_mc_action_iter_1 (void);
extern int exceptions_state_mc_catch (struct gdb_exception *, int);
-/* Same, but for the C++ try/catch-based TRY/CATCH mechanism. */
+/* For the C++ try/catch-based TRY/CATCH mechanism. */
-#if GDB_XCPT != GDB_XCPT_SJMP
extern void *exception_try_scope_entry (void);
extern void exception_try_scope_exit (void *saved_state);
extern void exception_rethrow (void) ATTRIBUTE_NORETURN;
-#endif
/* Macro to wrap up standard try/catch behavior.
@@ -196,19 +178,6 @@ extern void exception_rethrow (void) ATTRIBUTE_NORETURN;
#define END_CATCH_SJLJ \
}
-#if GDB_XCPT == GDB_XCPT_SJMP
-
-/* If using SJLJ-based exceptions for all exceptions, then provide
- standard aliases. */
-
-#define TRY TRY_SJLJ
-#define CATCH CATCH_SJLJ
-#define END_CATCH END_CATCH_SJLJ
-
-#endif /* GDB_XCPT_SJMP */
-
-#if GDB_XCPT == GDB_XCPT_TRY || GDB_XCPT == GDB_XCPT_RAW_TRY
-
/* Prevent error/quit during TRY from calling cleanups established
prior to here. This pops out the scope in either case of normal
exit or exception exit. */
@@ -226,8 +195,6 @@ struct exception_try_scope
void *saved_state;
};
-#if GDB_XCPT == GDB_XCPT_TRY
-
/* We still need to wrap TRY/CATCH in C++ so that cleanups and C++
exceptions can coexist.
@@ -263,15 +230,6 @@ struct exception_try_scope
} \
}
-#else
-
-#define TRY try
-#define CATCH(EXCEPTION, MASK) \
- catch (struct gdb_exception ## _ ## MASK &EXCEPTION)
-#define END_CATCH
-
-#endif
-
/* The exception types client code may catch. They're just shims
around gdb_exception that add nothing but type info. Which is used
is selected depending on the MASK argument passed to CATCH. */
@@ -288,8 +246,6 @@ struct gdb_exception_RETURN_MASK_QUIT : public gdb_exception_RETURN_MASK_ALL
{
};
-#endif /* GDB_XCPT_TRY || GDB_XCPT_RAW_TRY */
-
/* An exception type that inherits from both std::bad_alloc and a gdb
exception. This is necessary because operator new can only throw
std::bad_alloc, and OTOH, we want exceptions thrown due to memory