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Re: [patch] Unified debug dump function names.


On 3/27/13, Richard Biener <richard.guenther@gmail.com> wrote:
> On Mar 27, 2013, Lawrence Crowl <crowl@googlers.com> wrote:
>> Patch with rename to debug attached.
>> Tested on x86_64.
>>
>>
>> Add uniform debug dump function names.
>>
>>
>> Add some overloaded functions that provide uniform debug dump
>> function names.  These names are:
>>
>>   debug: the general debug dumper
>>   debug_verbose: for more details
>>   debug_raw: for the gory details
>>   debug_head: for the heads of declarations, e.g. function heads
>>   debug_body: for the bodies of declarations, e.g. function bodies
>>
>> Not all types have the last four versions.
>>
>> The debug functions come in two flavors, those that take pointers
>> to the type, and those that take references to the type.  The first
>> handles printing of '<nil>' for null pointers.  The second assumes
>> a valid reference, and prints the content.
>>
>>
>> Example uses are as follows:
>>
>>   cp_token t, *p;
>>   debug (t);
>>   debug (p);
>>
>> From the debugger, use
>>
>>   call debug (t)
>>
>>
>> The functions sets implemented are:
>>
>> debug (only)
>>
>>     basic_block_def, const bitmap_head_def, cp_binding_level,
>>     cp_parser, cp_token, data_reference, die_struct, edge_def,
>>     gimple_statement_d, ira_allocno, ira_allocno_copy, live_range,
>>     lra_live_range, omega_pb_d, pt_solution, const rtx_def, sreal,
>>     tree_live_info_d, _var_map,
>>
>>     vec<cp_token, va_gc>, vec<data_reference_p>, vec<ddr_p>,
>>     vec<rtx>, vec<tree, va_gc>,
>>
>> debug and debug_raw
>>
>>     simple_bitmap_def
>>
>> debug and debug_verbose
>>
>>     expr_def, struct loop, vinsn_def
>>
>> debug, debug_raw, debug_verbose, debug_head, debug_body
>>
>>     const tree_node
>>
>>
>> This patch is somewhat different from the original plan at
>> gcc.gnu.org/wiki/cxx-conversion/debugging-dumps.  The reason
>> is that gdb has an incomplete implementation of C++ call syntax;
>> requiring explicit specification of template arguments and explicit
>> specification of function arguments even when they have default
>> values.  So, the original plan would have required typing
>>
>>   call dump <cp_token> (t, 0, 0, stderr)
>>
>> which is undesireable.  Instead instead of templates, we overload
>> plain functions.  This adds a small burden of manually adding
>> the pointer version of dump for each type.  Instead of default
>> function arguments, we simply assume the default values.  Most of
>> the underlying dump functions did not use the options and indent
>> parameters anyway.  Several provide FILE* parameters, but we expect
>> debugging to use stderr anyway.  So, the explicit specification of
>> arguments was not as valuable as we thought initially.
>
> Note that generally modules should provide a
>
>  print_FOO (FILE *, FOO *...)
>
> interface which should be the worker for the dump_* interface
> which prints to dumpfiles (and stdout/stderr with -fopt-info) and
> the debug_* interface (which just prints to stderr).

I'm not sure what you're saying here.  I haven't been adding new
underlying functionality.  If there are missing print_FOO functions,
shouldn't they be a separate work item?

>> Finally, a change of name from dump to debug reflect the implicit
>> output to stderr.
>
> A few more questions.  As we are now using C++ and these
> functions are not called by GCC itself - do we really need
> all the extern declarations in the header files?  We don't have
> -Wstrict-prototypes issues with C++ and I do not consider the debug
> () interface part of the public API of a module.  This avoids
> people ending up calling debug () from inside GCC.

We don't need the extern declarations for gdb, but I've written
temporary calls to debug into the source code while I was developing.
It would be handy to not have to add declarations simultaneously.
Your call.

> +  if (ptr)
> +    debug (*ptr);
> +  else
> +    fprintf (stderr, "<nil>\n");
>
> can we avoid repeating this using a common helper?  I'd use a simple
> #define like
>
> #define DO_DEBUG_PTR(p) do { if (p) debug (*(p)) else fprintf (stderr,
> "<nil>\n"); } while (0)
>
> but I suppose you can come up with something more clever using C++?

I had a template that did this for us in my earlier code.  I removed
the template when I discovered the gdb issue.  One advantage to
removing the template was that I no longer needed a common header and
its inclusion in various files.  Adding the macro would reintroduce
the header.

My personal preference is to avoid the macros and just live with the
repeated pattern.

-- 
Lawrence Crowl


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