[Scons-users] Attaching an emitter to an existing builder

[Jeremy Elson]

Just wanted to ping yon on the PR above adding native mapfile support to
scons:

https://github.com/SCons/scons/compare/master...jelson:jelson/scons-mapfile

On Sat, Jan 30, 2021 at 4:07 PM Jeremy Elson <jelson at gmail.com> wrote:

> Hi Bill,
>
> I'd like to do better than file a bug -- how about a PR?
>
> https://github.com/SCons/scons/compare/master...jelson:jelson/scons-mapfile
>
> I don't have much experience with SCons internals, so I might have not
> done this in the most idiomatic way, but I'm open to suggestions how to
> improve it so I can make it into a PR. I tested this with a simple
> SConstruct file:
>
> Program('prog1.c')
> Program('prog2.c', mapfile='prog2.map')
> Program('prog3', source='prog1.c')
>
> It generates the output you would expect:
>
> gcc -o prog1.o -c prog1.c
> gcc -o prog1 prog1.o
> gcc -o prog2.o -c prog2.c
> gcc -o prog2 prog2.o -Wl,-Map=prog2.map,--cref
> gcc -o prog3 prog1.o
>
> If my implementation is way too off the mark to be useful, I'd be happy to
> just file a bug instead :)
>
> -Jeremy
>
>
> On Fri, Jan 29, 2021 at 10:58 AM Bill Deegan <bill at baddogconsulting.com>
> wrote:
>
>> Jeremy,
>>
>> Glad that worked for you!
>> Please consider filing an enhancement request issue to support generating
>> map files?
>>
>> Thanks,
>> Bill
>>
>> On Thu, Jan 28, 2021 at 4:20 PM Jeremy Elson <jelson at gmail.com> wrote:
>>
>>> Thanks, everyone for the help -- PROGEMITTER worked perfectly:
>>>
>>>         # Add map creation as a linker flag, and modify the standard
>>> Program
>>>         # emitter to know that map generation is a side-effect
>>>         map_filename = os.path.join(build_obj_dir, f"{target.name}.map")
>>>         env.Append(LINKFLAGS = f"-Wl,-Map={map_filename},--cref")
>>>         def map_emitter(target, source, env):
>>>             assert(str(target[0]) == os.path.abspath(program_name))
>>>             target.append(map_filename)
>>>             return target, source
>>>         env.Append(PROGEMITTER = [map_emitter])
>>>
>>> My only concern with PROGEMITTER was that it was not a general solution
>>> to this problem -- i.e., what if I want to override something other than
>>> Program()? But from looking at MSlink.py as Mats suggested, it seems that
>>> nearly all the standard builders have similar overrides (SHLIBEMITTER,
>>> LDMODULEEMITTER, etc). I guess it's similar to the *COMSTR series of
>>> constants for modifying the message printed at each build step.
>>>
>>> Thanks again for a great build system. SCons is a pleasure to use.
>>>
>>> -Jeremy
>>>
>>>
>>>
>>> On Thu, Jan 28, 2021 at 7:19 AM Mats Wichmann <mats at wichmann.us> wrote:
>>>
>>>> On 1/27/21 3:11 PM, Bill Deegan wrote:
>>>> > Jeremy,
>>>> >
>>>> > Greetings!
>>>> > You're not the first to mention adding the map file as a side effect.
>>>> > (or target)
>>>> > Please go ahead and file and Issue on github for this.
>>>> > Ideally with a simple example, what the gcc flag is, and what the
>>>> file
>>>> > naming/location would be?
>>>> >
>>>> > So likely the easiest way to add an emitter to Program() would be the
>>>> > following (not tested)
>>>> >
>>>> > env.Append(PROGEMITTER = [my_map_emitter])
>>>> >
>>>> > Give that a try and let us know if it works for you?
>>>> >
>>>> > Also there's a discord server for scons help if you'd like to ask
>>>> > questions/get help there.
>>>> > https://discord.gg/bXVpWAy <https://discord.gg/bXVpWAy>
>>>> >
>>>> > Hope that helps!
>>>> > -Bill
>>>>
>>>> For inspiration, the mslink tool does this (as does the qt tool) - see
>>>> the somewhat messy SCons/Tool/mslink.py.
>>>>
>>>> Meanwhile, while many tools use add_emitter, the code for add_emitter
>>>> itself includes this comment:
>>>>
>>>>          This assumes that emitter has been initialized with an
>>>>          appropriate dictionary type, and will throw a TypeError if
>>>>          not, so the caller is responsible for knowing that this is an
>>>>          appropriate method to call for the Builder in question.
>>>>
>>>> >              env["BUILDERS"]["Program"].add_emitter(
>>>> >                  suffix = ".map",
>>>> >                  emitter = map_emitter)
>>>> >
>>>> >     But it throws an exception:
>>>> >
>>>> >     TypeError: 'EmitterProxy' object does not support item assignment
>>>>
>>>> So I guess "expected"? although pretty awkward....
>>>>
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