From c6fdd8b2052baa9b7a27d4d34f109c9622b53509 Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Tue, 23 Apr 2019 07:29:49 -0600 Subject: [PATCH] Make SJLJ exceptions more efficient This changes the SJLJ exception handling code to be a bit more efficient, by using rvalue references and move assignment when possible. Tested by the buildbot. gdb/ChangeLog 2019-04-25 Tom Tromey * event-top.c (gdb_rl_callback_read_char_wrapper_noexcept) (gdb_rl_callback_handler): Use std::move. * common/common-exceptions.h (struct gdb_exception): Add move assignment operator. (throw_exception_sjlj): Change "exception" to const reference. * common/common-exceptions.c (exceptions_state_mc_catch): Update. (throw_exception_sjlj): Change "exception" to const reference. --- gdb/ChangeLog | 10 ++++++++++ gdb/common/common-exceptions.c | 5 +++-- gdb/common/common-exceptions.h | 4 +++- gdb/event-top.c | 6 +++--- 4 files changed, 19 insertions(+), 6 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 106f0e65bbe..809df468443 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,13 @@ +2019-04-25 Tom Tromey + + * event-top.c (gdb_rl_callback_read_char_wrapper_noexcept) + (gdb_rl_callback_handler): Use std::move. + * common/common-exceptions.h (struct gdb_exception): Add move + assignment operator. + (throw_exception_sjlj): Change "exception" to const reference. + * common/common-exceptions.c (exceptions_state_mc_catch): Update. + (throw_exception_sjlj): Change "exception" to const reference. + 2019-04-25 Tom Tromey * xml-support.c (gdb_xml_parser::gdb_xml_parser): Update. diff --git a/gdb/common/common-exceptions.c b/gdb/common/common-exceptions.c index 59c27ab52d4..0b96cc679da 100644 --- a/gdb/common/common-exceptions.c +++ b/gdb/common/common-exceptions.c @@ -166,14 +166,15 @@ exceptions_state_mc_action_iter_1 (void) /* Return EXCEPTION to the nearest containing CATCH_SJLJ block. */ void -throw_exception_sjlj (struct gdb_exception exception) +throw_exception_sjlj (const struct gdb_exception &exception) { /* Jump to the nearest CATCH_SJLJ block, communicating REASON to that call via setjmp's return value. Note that REASON can't be zero, by definition in common-exceptions.h. */ exceptions_state_mc (CATCH_THROWING); + enum return_reason reason = exception.reason; catchers.front ().exception = exception; - longjmp (catchers.front ().buf, exception.reason); + longjmp (catchers.front ().buf, reason); } /* Implementation of throw_exception that uses C++ try/catch. */ diff --git a/gdb/common/common-exceptions.h b/gdb/common/common-exceptions.h index 33fa8a92ec2..d7b25502262 100644 --- a/gdb/common/common-exceptions.h +++ b/gdb/common/common-exceptions.h @@ -152,6 +152,8 @@ struct gdb_exception return *this; } + gdb_exception &operator= (gdb_exception &&other) noexcept = default; + /* Return the contents of the exception message, as a C string. The string remains owned by the exception object. */ const char *what () const noexcept @@ -281,7 +283,7 @@ extern void throw_exception (const gdb_exception &exception) containing exception handler established using TRY_SJLJ. Necessary in some cases where we need to throw GDB exceptions across third-party library code (e.g., readline). */ -extern void throw_exception_sjlj (struct gdb_exception exception) +extern void throw_exception_sjlj (const struct gdb_exception &exception) ATTRIBUTE_NORETURN; /* Convenience wrappers around throw_exception that throw GDB diff --git a/gdb/event-top.c b/gdb/event-top.c index 959792d9e7a..bb8ba5cfe57 100644 --- a/gdb/event-top.c +++ b/gdb/event-top.c @@ -178,7 +178,7 @@ gdb_rl_callback_read_char_wrapper_noexcept () noexcept } CATCH_SJLJ (ex, RETURN_MASK_ALL) { - gdb_expt = ex; + gdb_expt = std::move (ex); } END_CATCH_SJLJ @@ -212,9 +212,9 @@ gdb_rl_callback_handler (char *rl) noexcept { ui->input_handler (gdb::unique_xmalloc_ptr (rl)); } - catch (const gdb_exception &ex) + catch (gdb_exception &ex) { - gdb_rl_expt = ex; + gdb_rl_expt = std::move (ex); } /* If we caught a GDB exception, longjmp out of the readline -- 2.30.2