Re: [PATCH 00/12] remove some cleanups using a cleanup function

[Andrew Burgess <andrew.burgess@embecosm.com>]

I've been thinking about a similar idea for a while too.  I wondered
if there was a way we could make use of templates to generate some of
the common boiler plate cleanups.

This mini-series changes the first 4 of your patches to you this idea
so you can see how it might work.

First, the ideal, description, a new templated class
`cleanup_function` that allows you to do something like this:

    void
    delete_longjmp_breakpoint (int arg)
    {
      /* Blah, blah, blah...  */
    }

    using longjmp_breakpoint_cleanup
        = cleanup_function <delete_longjmp_breakpoint, int>;

This creates a new cleanup class `longjmp_breakpoint_cleanup` than can
then be used like this:

    longjmp_breakpoint_cleanup obj (thread);

    /* Blah, blah, blah...  */

    obj.cancel ();  /* Optional cancel if needed.  */

The cleanup_function class can take any number of arguments, and is
cancellable if needed, it can also take zero arguments.  In theory
this would allow any cleanup that only needs to hold some simple
arguments by value and call a static function to be made into a
`cleanup_function` specialisation.

Now the only slight problem is that the above requires C++17, which
isn't what we use right now. However, there is a C++11 alternative
which we can use for now, so you _actually_ have to write this:

    using longjmp_breakpoint_cleanup
        = cleanup_function <void (*) (int), delete_longjmp_breakpoint, int>;

The function signature is added in as pre-C++17 GCC doesn't support
`auto` template parameters.

The 4 patches below make use of `#ifdef __cpp_template_auto` to
demonstrate the pre and post C++17 code variants.  A final submission
would be based on pre-C++11 and include the function signatures, but
add a comment in the `cleanup_function` class that when we update the
C++ standard, we can update how the class is used.

How do you think this compares to your original patches?  Any interest
in this approach?

Thanks,
Andrew


--

Andrew Burgess (4):
  gdb: Remove delete_longjmp_breakpoint_cleanup
  gdb: Remove remaining cleanup from breakpoint.c
  gdb: Remove make_bpstat_clear_actions_cleanup
  gdb/testsuite: Don't allow paths to appear in test name

 gdb/ChangeLog                 |  29 +++++++++++
 gdb/breakpoint.c              |  26 +++-------
 gdb/breakpoint.h              |  19 +++++++
 gdb/common/cleanup-function.h | 118 ++++++++++++++++++++++++++++++++++++++++++
 gdb/infcmd.c                  |  12 +----
 gdb/inferior.h                |   2 -
 gdb/infrun.c                  |   7 +--
 gdb/testsuite/ChangeLog       |   4 ++
 gdb/top.c                     |   7 ++-
 gdb/utils.c                   |  17 ------
 gdb/utils.h                   |   1 -
 11 files changed, 187 insertions(+), 55 deletions(-)
 create mode 100644 gdb/common/cleanup-function.h

-- 
2.14.5