[bug #47421] Add support for doing plugin macro overloading

[Brian Vandenberg]

URL:
  <http://savannah.gnu.org/bugs/?47421>

                 Summary: Add support for doing plugin macro overloading
                 Project: make
            Submitted by: phantal
            Submitted on: Tue 15 Mar 2016 04:30:57 PM GMT
                Severity: 3 - Normal
              Item Group: Enhancement
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
       Component Version: 4.1
        Operating System: Any
           Fixed Release: None
           Triage Status: None

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Details:

As a preface: I recognize that what I outline below could be done in other
ways with existing make syntax.  I'm not interested in suggestions for
alternative ways to get similar results.

----

I had a situation arise a few weeks ago where I had wanted to be able to do
macro overloading.

I was experimenting with adding support for namespace-scoped variables.

I had originally written it as one function (each namespace was registered to
the same function) but its execution time was rather high.  I tested its
expansion time with another macro I wrote for repeatedly expanding expressions
to see the avg/std of the expansion time.

I had thought the problem might be the conditional logic.  As a test I broke
it up into separate macros with different names and it improved performance by
an order of magnitude, but it was syntactically awkward because I needed a
separate macro name for listing, setting, and getting as opposed to the more
concise example below.

I'm using C++14 with gnu extensions for my plugin, but the syntax should make
it obvious what I'm doing.  Here's a sketch of what I had going:


extern "C" {
#include <gnumake.h>
}

using plugin_function_t = typeof(*gmk_func_ptr());

plugin_function_t namespace_list;
plugin_function_t namespace_add;

plugin_function_t variable_list;
plugin_function_t variable_getter;
plugin_function_t variable_setter;

/*...*/

gmk_add_function( gmk_api::strdup( "namespace" ), namespace_list, 0, 0,
GMK_FUNC_DEFAULT );
gmk_add_function( gmk_api::strdup( "namespace" ), namespace_add, 1, 1,
GMK_FUNC_DEFAULT );

/*...*/

gmk_add_function( gmk_api::strdup( argv[0], variable_list, 0, 0,
GMK_FUNC_DEFAULT );
gmk_add_function( gmk_api::strdup( argv[0], variable_getter, 1, 1,
GMK_FUNC_DEFAULT );
gmk_add_function( gmk_api::strdup( argv[0], variable_setter, 2, 2,
GMK_FUNC_DEFAULT );


... where it could be used like this:


$(namespace asdf)
$(namespace fdsa)
$(asdf name1, value1)
$(asdf name2, value2)
$(asdf name3, value3)
$(fdsa name1, value1)
$(fdsa name2, value2)
$(fdsa name3, value3)
$(info Namespaces: $(namespace ))
$(foreach x,\
  $(namespace ) \
, $(foreach y,\
  $(${x} ) \
, $(info In namespace ${x}, variable ${y} = $(${x} ${y})) \
))






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