Re: Makefile or IDE?

From	David Brown <david.brown@hesbynett.no>
Newsgroups	comp.arch.embedded
Subject	Re: Makefile or IDE?
Date	2021-12-05 13:21 +0100
Organization	A noiseless patient Spider
Message-ID	<soiasv$q97$1@dont-email.me> (permalink)
References	<soabn8$b4e$1@dont-email.me> <soe6rf$brb$1@dont-email.me> <sofg1s.13g.1@stefan.msgid.phost.de> <sog15s$uj0$1@dont-email.me> <soi6p9.12g.1@stefan.msgid.phost.de>

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On 05/12/2021 11:11, Stefan Reuther wrote:
> Am 04.12.2021 um 16:23 schrieb pozz:
>> Il 04/12/2021 10:31, Stefan Reuther ha scritto:
>>> I'm not sure what you need order-only dependencies for. For a project
>>> like this, with GNU make I'd most likely just do something like
>>>
>>>      OBJ = file1.o module1/file2.o module2/file3.o
>>>      main: $(OBJ)
>>>           $(CC) -o $@ $(OBJ)
>>>      $(OBJ): %.o: $(SRCDIR)/%.c
>>>           mkdir $(dir $@)
>>>           $(CC) $(CFLAGS) -c $< -o $@
>>
>> This is suboptimal. Every time one object file is created (because it is
>> not present or because prerequisites aren't satisfied), mkdir command is
>> executed, even if $(dir $@) is already created.
> 
> (did I really forget the '-p'?)
> 
> The idea was that creating a directory and checking for its existence
> both require a path lookup, which is the expensive operation here.
> 

Checking for the path is not expensive - it is already necessary to have
the path details read from the filesystem (and therefore cached, even on
Windows) because you want to put a file in it.  So it is free.  "mkdir
-p" is also very cheap - it only needs to do something if the path does
not exist.  (Of course, on Windows starting any process takes time and
resources an order of magnitude or more greater than on *nix.)  It is
always nice to avoid unnecessary effort, as even small inefficiencies
add up if there are enough of them.  But there's no need to worry unduly
about the small things.

> When generating the Makefile with a script, it's easy to sneak a 100%
> matching directory creation dependency into any rule that needs it
> 
>      foo/bar.o: bar.c foo/.mark
>           ...
>      foo/.mark:
>           mkdir foo
> 

And it's easy to forget the "touch foo/.mark" command to make that work!

But that is completely unnecessary - make is perfectly capable of
working with a directory as a dependency and target (especially as an
order-only dependency).

>>>> Dependencies must be created as a side effect of compilation with
>>>> esoteric -M options for gcc.
>>>
>>> It's not too bad with sufficiently current versions.
>>>
>>>      CFLAGS += -MMD -MP
>>>      -include $(OBJ:.o=.d)
>>
>> Are you sure you don't need -MT too, to specify exactly the target rule?
> 
> Documentation says you are right, but '-MMD -MP' works fine for me so far...
> 
> 
>   Stefan
>

Thread

Makefile or IDE? pozz <pozzugno@gmail.com> - 2021-12-02 12:46 +0100
  Re: Makefile or IDE? Grant Edwards <invalid@invalid.invalid> - 2021-12-02 15:22 +0000
    Re: Makefile or IDE? pozz <pozzugno@gmail.com> - 2021-12-02 17:34 +0100
      Re: Makefile or IDE? Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-12-03 13:15 +0200
  Re: Makefile or IDE? Don Y <blockedofcourse@foo.invalid> - 2021-12-02 09:48 -0700
  Re: Makefile or IDE? Stefan Reuther <stefan.news@arcor.de> - 2021-12-02 17:34 +0100
    Re: Makefile or IDE? pozz <pozzugno@gmail.com> - 2021-12-03 11:49 +0100
      Re: Makefile or IDE? Stefan Reuther <stefan.news@arcor.de> - 2021-12-03 18:27 +0100
    Re: Makefile or IDE? George Neuner <gneuner2@comcast.net> - 2021-12-04 14:37 -0500
  Re: Makefile or IDE? Theo <theom+news@chiark.greenend.org.uk> - 2021-12-03 20:51 +0000
    Re: Makefile or IDE? Grant Edwards <invalid@invalid.invalid> - 2021-12-03 21:28 +0000
      Re: Makefile or IDE? George Neuner <gneuner2@comcast.net> - 2021-12-04 14:53 -0500
        Re: Makefile or IDE? David Brown <david.brown@hesbynett.no> - 2021-12-04 22:17 +0100
          Re: Makefile or IDE? Stefan Reuther <stefan.news@arcor.de> - 2021-12-05 11:02 +0100
            Re: Makefile or IDE? David Brown <david.brown@hesbynett.no> - 2021-12-05 13:16 +0100
        Re: Makefile or IDE? Grant Edwards <invalid@invalid.invalid> - 2021-12-06 13:52 +0000
          Re: Makefile or IDE? chris <chris-nospam@tridac.net> - 2021-12-17 17:19 +0000
  Re: Makefile or IDE? pozz <pozzugno@gmail.com> - 2021-12-03 23:48 +0100
    Re: Makefile or IDE? Stefan Reuther <stefan.news@arcor.de> - 2021-12-04 10:31 +0100
      Re: Makefile or IDE? pozz <pozzugno@gmail.com> - 2021-12-04 16:23 +0100
        Re: Makefile or IDE? David Brown <david.brown@hesbynett.no> - 2021-12-04 17:41 +0100
          Re: Makefile or IDE? Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-12-04 18:49 +0200
            Re: Makefile or IDE? David Brown <david.brown@hesbynett.no> - 2021-12-04 18:23 +0100
              Re: Makefile or IDE? Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-12-04 21:25 +0200
                Re: Makefile or IDE? David Brown <david.brown@hesbynett.no> - 2021-12-04 22:20 +0100
                Re: Makefile or IDE? Grant Edwards <invalid@invalid.invalid> - 2021-12-06 13:51 +0000
                Re: Makefile or IDE? David Brown <david.brown@hesbynett.no> - 2021-12-06 16:33 +0100
                Re: Makefile or IDE? Grant Edwards <invalid@invalid.invalid> - 2021-12-06 16:02 +0000
          Re: Makefile or IDE? pozz <pozzugno@gmail.com> - 2021-12-09 11:54 +0100
            Re: Makefile or IDE? Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2021-12-10 18:35 +0100
              Re: Makefile or IDE? David Brown <david.brown@hesbynett.no> - 2021-12-10 19:44 +0100
                Re: Makefile or IDE? pozz <pozzugno@gmail.com> - 2021-12-11 16:18 +0100
                Re: Makefile or IDE? David Brown <david.brown@hesbynett.no> - 2021-12-11 17:06 +0100
                Re: Makefile or IDE? Grant Edwards <invalid@invalid.invalid> - 2021-12-11 16:57 +0000
                Re: Makefile or IDE? Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2021-12-11 18:53 +0100
                Re: Makefile or IDE? David Brown <david.brown@hesbynett.no> - 2021-12-12 14:15 +0100
              Re: Makefile or IDE? Stefan Reuther <stefan.news@arcor.de> - 2021-12-11 10:01 +0100
                Re: Makefile or IDE? Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2021-12-11 18:47 +0100
                Re: Makefile or IDE? Stefan Reuther <stefan.news@arcor.de> - 2021-12-12 11:27 +0100
        Re: Makefile or IDE? Stefan Reuther <stefan.news@arcor.de> - 2021-12-05 11:11 +0100
          Re: Makefile or IDE? David Brown <david.brown@hesbynett.no> - 2021-12-05 13:21 +0100
  Re: Makefile or IDE? Dave Nadler <drn@nadler.com> - 2021-12-06 15:45 -0500
  Re: Makefile or IDE? pozz <pozzugno@gmail.com> - 2021-12-09 10:43 +0100
  Re: Makefile or IDE? Johann Klammer <klammerj@NOSPAM.a1.net> - 2021-12-10 09:30 +0100
  Re: Makefile or IDE? chris <chris-nospam@tridac.net> - 2021-12-17 17:27 +0000
    Re: Makefile or IDE? StateMachineCOM <statemachineguru@gmail.com> - 2021-12-20 17:18 -0800
      Re: Makefile or IDE? chris <chris-nospam@tridac.net> - 2021-12-21 16:45 +0000
      Re: Makefile or IDE? Jim Jackson <jj@franjam.org.uk> - 2021-12-21 17:40 +0000
        Re: Makefile or IDE? StateMachineCOM <statemachineguru@gmail.com> - 2021-12-21 10:55 -0800

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