220 24706 article Path: news.gmane.org!not-for-mail From: Abyx Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Modules are hard for build tools Date: Fri, 26 Feb 2016 07:23:56 -0800 (PST) Lines: 454 Approved: news@gmane.org Message-ID: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_99_1784697087.1456500236418" X-Trace: ger.gmane.org 1456500265 21755 80.91.229.3 (26 Feb 2016 15:24:25 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 26 Feb 2016 15:24:25 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCE4FQ4JYQLBBDO4YG3AKGQEOG4OWUY@isocpp.org Fri Feb 26 16:24:07 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-io0-f197.google.com ([209.85.223.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1aZKFQ-0003oR-97 for gclcip-std-proposals@m.gmane.org; Fri, 26 Feb 2016 16:24:04 +0100 Original-Received: by mail-io0-f197.google.com with SMTP id t64sf156611848ioe.0 for ; Fri, 26 Feb 2016 07:23:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=OFXeDDGuVFEePZ4l3i3/83aH072raTpsfY4CRrAW9zg=; b=pRArtLzTSzSCPa2ZAac7JHxlWkBk3opJbYvuUSdkx7xs9K6EqziKopzB7hfoTq23Xh Wvm5Qc3sUk5EtTU49Pwy/UQACnaMkxOmf6pA9DpnvbIDEQd+E1fk5ig0OJ8nk6xyFZS5 FIBn8TDgCw6xE5sCXNmiRtpI3UXfnBMcqs7AI33leoF/svLzd8WRFuEdCADYgSCahNsf NFx0lrXXqBLvMQYWo+mnLRXYxYaX62UKnlY2O19bnxJdd0uBPSHZU9nRLAEJw4snYGlx CPlc0Hi3Quodpb6w12KVM44iQNDdJBYr9EChMF/P9FVq3tCTfSDcq9feSQm48TvS4RCx E+yw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=OFXeDDGuVFEePZ4l3i3/83aH072raTpsfY4CRrAW9zg=; b=u/lARxIYIKtU1EkV1usZmtyyinZq4+SlzoH1i/sedVVfvzyzEx78ljup/FQk6hy/Jn AmHR8QG1XTRu7wvJTr4bsxqObj93eXBmAebSEhVRBPLUKZeYLXGRqs/xl3J1Ib1EFh3S St0lKI2rkxclkgGqjL8z5b1xVwF8VHsU62Ghj7JKLoN5WEmOcX5SbxlEFmhAj5I++v1r 2XlD4olOOgB0pi1fwiwfphDaTOS/Hn4O1h9zCPwnGXqXZ+Toxu8FLEUBz38OJ0wlk9dn 4FzB86vm0uPNtJ4PHX+C9Cbnk3CblbmSO3yQ2P4VrMqxOnQkbeluz5y3cwMTGuO01OWh Pymw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:message-id:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=OFXeDDGuVFEePZ4l3i3/83aH072raTpsfY4CRrAW9zg=; b=IQRUOCETKYc4LjOo0+0/DegUXLlZc/jVRuU8/YLHM6dibcsc+bou3333DDqowbc+9f aiFU6mv02wPf5r9PJ8obPX/l+UNbXylYiMU1MNNadPDGA4Ehw73vbRyIEinzZETIgyH0 CKWDhbzG003NqgV9AxwgtStrJ+p1gCt4rqzf29pp40Wz7WIKVNM+WhWsneipJcWlOIWO zFxdSC9967G30okE/zLpr17b9MaMy93EEE6Xgsy6UCIgzkm9ijemQzKRQJA11tdfdsaY QYD+k6IT9Z9mW4LD+U7Smkw4l39V7zpV8UQn4b6cexS9mQI3HcmvXhIhHwBT5GU79XfB hJ3A== X-Gm-Message-State: AD7BkJKe8wE6SJzyvQA/onCsS5vcg0Y5DnU1pr3PZ+B4zmLz+24mMSomVPjM8YZuli3NbA== X-Received: by 10.50.47.40 with SMTP id a8mr2605202ign.6.1456500238476; Fri, 26 Feb 2016 07:23:58 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.108.20 with SMTP id hg20ls552225igb.39.canary; Fri, 26 Feb 2016 07:23:57 -0800 (PST) X-Received: by 10.50.183.36 with SMTP id ej4mr56326igc.1.1456500237420; Fri, 26 Feb 2016 07:23:57 -0800 (PST) X-Original-Sender: fl.lllj@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:24706 Archived-At: ------=_Part_99_1784697087.1456500236418 Content-Type: multipart/alternative; boundary="----=_Part_100_446552970.1456500236420" ------=_Part_100_446552970.1456500236420 Content-Type: text/plain; charset=UTF-8 Without modules we have the following situation: There is a bunch of source files with code - tu1.cpp, tu2.cpp, ..., tuN.cpp, h1.hpp, h2.hpp, ..., hM.hpp, And a build tool script (*make, gyp, gn, etc) add_executable(my_app, tu1.cpp, tu2.cpp, ..., tuN.cpp) The build tool have to preprocess all the .cpp files, find all the "#include" directives and generate the build rules: # target dependencies tu1.cpp.o : tu1.cpp, hA.hpp, ..., hX.hpp ... tuN.cpp.o : tuN.cpp, hB.hpp, ..., hY.hpp my_app : tu1.cpp.o, ..., tuN.cpp.o Note that the *.o targets don't depend on each other and can be compiled in-parallel. -------------------------------------------- Modules add the module interface translation units (I'll call it an *.ixx file) and compiled module exports (an *.ifc file) If a translation unit A.cpp imports a module B, then it depends on B.ifc which depends on B.ixx. So if we have the following source files (for simplicity let's not use header files) a_tu1.ixx, a_tu2.cpp (imports B), ..., a_tuN.cpp // module A b_tu1.ixx (imports A), b_tu2.cpp, ..., b_tuM.cpp // module B ... m_tu1.ixx, m_tu2.cpp, ..., m_tuM.cpp // module M This means that a build tool have to produce the following build rules: # targets dependencies a_tu1.ixx.o, A.ifc : a_tu1.ixx b_tu1.ixx.o, B.ifc : b_tu1.ixx, A.ifc ... m_tu1.ixx.o, M.ifc : m_tu1.ixx, X.ifc, ..., Y.ifc a_tu2.cpp.o : a_tu2.cpp, B.ifc ... m_tuN.cpp.o : m_tuN.cpp, X.ifc, ..., Y.ifc my_app : a_tu1.ixx.o, ..., m_tuN.cpp.o And now we have *.o targets which depend on *.ifc targets, and *.ifc targets which depend on other *.ifc targets. So what should we write in our build tool script, so it would generate such build rules? It would be great if we could just write down all the translation units: add_executable(my_app, a_tu1.ixx.o, ..., a_tuN.cpp.o) But then the build tool would have to not only preprocess C++ code (to find all the #include directives), but also parse it, in order to find the import statements. It's not practical to manually write all the dependencies in the build script, because this would just duplicate the import statements in the code: add_module_dependencies(A, b_tu1.ixx, ..., x_tuX.cpp) add_module_dependencies(B, a_tu2.cpp, ..., y_tuY.cpp) -- or -- add_module_dependencies(b_tu1.ixx, A) add_module_dependencies(a_tu2.cpp, B) -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/a9ff0d91-dea2-49f1-8285-072732360d60%40isocpp.org. ------=_Part_100_446552970.1456500236420 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Without modules we have the following situation:

Th= ere is a bunch of source files with code -

=C2=A0 =C2=A0 tu1.cpp, tu2.cpp, ..., tuN.cpp,
=C2=A0 =C2=A0 h1.hpp, h2.hpp, ..., hM.hpp,

And a build tool script (*make, gyp,= gn, etc)

=C2=A0 =C2=A0 add_executable(my_app, tu1.cpp, tu2.cpp, ..., tuN.cpp)
=

The build tool have to preprocess all the .cpp files, find all th= e "#include" directives and generate the build rules:

=C2=A0 =C2=A0 # target =C2= =A0 =C2=A0dependencies
=C2=A0 =C2=A0 tu1.cpp.o= :<= span style=3D"color: #000;" class=3D"styled-by-prettify"> tu1.cpp, hA.hpp, ..., hX.hpp
=C2=A0 =C2=A0 ...
=C2=A0 =C2=A0 tuN.cpp.o : tuN.cpp<= /span>, hB.hpp, ..., hY.hpp
= =C2=A0 =C2=A0 my_app =C2=A0 =C2=A0: tu1.= cpp.o, ..., tuN.cpp.o
=

Note that the *.o targets don't depend on= each other and can be compiled in-parallel.

-----------------------= ---------------------

Modules add the module interface translation u= nits (I'll call it an *.ixx file) and compiled module exports (an *.ifc= file)
If a translation unit A.cpp imports a module B, then it depends = on B.ifc which depends on B.ixx.

So if we have the following source = files (for simplicity let's not use header files)

=C2=A0 =C2=A0 a_tu1= .ixx, a_tu2.cpp (imports B), ..., a_tuN.cpp // module A
=C2=A0 =C2=A0 b_tu1.ixx (imports A), b_tu2.cpp,<= /span> ..., b_tuM.cpp // module B
=C2=A0 =C2=A0 ...
=C2=A0 =C2=A0 m_tu1.ixx, m_tu2.cpp, ..., m_tuM.cpp // module M
This means that a build tool have to produce the following build rules:
=C2=A0= =C2=A0 # = targets =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 dependencies
=C2=A0 =C2=A0 a_tu1= .ixx.o, A.ifc =C2=A0: a= _tu1.ixx
=C2=A0 = =C2=A0 b_tu1.ixx.o, B.ifc =C2=A0: b_tu1.ixx, A.ifc
=C2=A0 =C2=A0 ...
=C2=A0 =C2=A0 m_tu1.ixx.o, M.if= c =C2=A0:<= /span> m_tu1.ixx, X.ifc, ..., Y.ifc
=C2=A0 =C2=A0 a_tu2.cpp.o =C2=A0 =C2=A0 =C2=A0 =C2=A0 = : a_tu2.cpp, B.ifc
=C2=A0 =C2=A0 ...
=C2=A0 =C2=A0 m_tuN.cpp.o= =C2=A0 =C2=A0 =C2=A0 =C2=A0 : m_tuN.cpp= , X.ifc, ..., Y.ifc
= =C2=A0 =C2=A0 my_app =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0: a_tu1.ixx.o, ...= , m_tuN.cpp.o

An= d now we have *.o targets which depend on *.ifc targets, and *.ifc targets = which depend on other *.ifc targets.

So what should we write in our = build tool script, so it would generate such build rules?

It would b= e great if we could just write down all the translation units:

= =C2=A0 =C2=A0 add= _executable(my_app, a_tu1.ixx.o, ..= .., a_tuN.cpp.o)

But then the bu= ild tool would have to not only preprocess C++ code (to find all the #inclu= de directives), but also parse it, in order to find the import statements.<= br>
It's not practical to manually write all the dependencies in the= build script, because this would just duplicate the import statements in t= he code:

=C2=A0 =C2=A0 add_module_dependencies(A, b_tu1.ixx, ..., x_tuX.cpp)
=C2=A0 =C2=A0 add_module_dependencies(B, a_tu2.c= pp,= ..., y_tuY.cpp)
=C2=A0 =C2=A0 -- or = --<= span style=3D"color: #000;" class=3D"styled-by-prettify">
=C2=A0 =C2=A0 = add_module_dependencies(b_tu1.= ixx= , A)
=C2=A0 =C2=A0 add_module_dependencies(a_tu2.cpp, B)


--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/a9ff0d91-dea2-49f1-8285-072732360d60= %40isocpp.org.
------=_Part_100_446552970.1456500236420-- ------=_Part_99_1784697087.1456500236418-- .