qmake SUBDIRS Project Automatic Dependencies

Here’s what I searched for, before figuring out how to get?SUBDIRSdependencies working using?qmake:

“qmake export compiler flags”
“qmake export defines”
“qmake export includepath”
“qmake build dependent projects”
“qt creator automatically build dependent libraries”

Problem 1: Detecting Dependency Changes

Qt Creator has some weird behaviors. As in, it doesn’t properly do dependent library builds all of the time, particularly when you’re using a?SUBDIRS?project template. I noticed that I would always have to right-click a project and “Run qmake” before running “Build X Project”, which was annoying. And I noticed that libraries wouldn’t automatically build and link to their consuming executables. It didn’t make sense, as I had used the “Add Library” option to add configuration blocks, like the following, to the executable project files that needed them:

win32:CONFIG(release,?debug|release):?LIBS?+=?-L$$OUT_PWD/../SomeLibrary/release/?-lSomeLibrary else:win32:CONFIG(debug,?debug|release):?LIBS?+=?-L$$OUT_PWD/../SomeLibrary/debug/?-lSomeLibrary else:unix:?LIBS?+=?-L$$OUT_PWD/../SomeLibrary/?-lSomeLibraryINCLUDEPATH?+=?$$PWD/../SomeLibrary/source DEPENDPATH?+=?$$PWD/../SomeLibrary/sourcewin32:CONFIG(release,?debug|release):?PRE_TARGETDEPS?+=?$$OUT_PWD/../SomeLibrary/release/SomeLibrary.lib else:win32:CONFIG(debug,?debug|release):?PRE_TARGETDEPS?+=?$$OUT_PWD/../SomeLibrary/debug/SomeLibrary.lib else:unix:?PRE_TARGETDEPS?+=?$$OUT_PWD/../SomeLibrary/libSomeLibrary.a

Once that block was in place, I figured all would be good. However, all that Qt Creator would do is tell me was thatlibSomeLibrary.a?wasn’t available, if I’d run a Clean on all of the projects, rather than just building and linking it for me. As in,?makewould?know?the library file was missing (via the?TARGET_PREDEPSsetting), but it would be too stupid to just build that target. And it wasn’t clear that any changes to?SomeLibrary?were being built and linked into the consuming executable, since?SomeLibrary?wasn’t getting autobuilt as a dependency. It seemed like old?SomeLibrarycode was getting linked instead, and only the executable’s changed code was getting recompiled before the link. This was a dependency nightmare in the making.

On all of these particular points, the?qmake manual?does not clarify that?SUBDIRS?projects are essentially a completely different beast, and require different rules to set up.

Not so useful.

The way to properly define dependencies in a?SUBDIRS?project is to use a master Project file that looks something like:

cache()TEMPLATE?=?subdirsSUBDIRS?+=?\ConsoleTest?\????????#?an?"app"?projectSomeLibrary?\????????#?a??"lib"?projectSomeExternalLibrary??#?a??"lib"?project#?ConsoleTest.subdir?is?implicitly?set?to?"ConsoleTest".SomeLibrary.subdir?????????=?SomeLibrary SomeExternalLibrary.subdir?=?external/SomeExternalLibrary#?Here's?where?you?build?up?the?hierarchical?relationship?between?components.SomeLibrary.depends?=?SomeExternalLibrary ConsoleTest.depends?=?SomeLibrary

This is all you need to do. The next time the project file is parsed and?qmake?is run to generate the platform-specific?Makefiles, it will generate the dependencies properly. No more weird builds and dependency problems. As much as I appreciate Qt’s awesome software, this is something they really need to clarify how to get working in their manual.

Problem 2: Exporting?DEFINES?and?INCLUDEPATH

In addition to the above, the method to set up the various projects to export the?qmake?DEFINES?and?INCLUDEPATH?flags used to build them was not clear from the documentation.

What you want in a hierarchical project configuration, ideally, is that the whole project rebuilds if any of the library sources, includes, included folders, or compiler?DEFINES?changes. You want any library consumers to use the exact same settings used to build the libraries, and you want this to happen if the setting changes in a single, authoritative place (preferably the library build configuration). The only reference I could find to?“library dependencies”?in the qmake manual is not clear as to its mechanism for propagating this information, particularly theINCLUDEPATH?and?DEFINES?settings.

After reading a handful of other references (1), (2), I finally figured out how to do this. It turns out that qmake has a lot of power to it, but that power is buried in bad documentation. (Why does no one invest in documentation? It’s an excellent opportunity to generate goodwill.)

The trick is twofold:

For each library project, you need to split the declaration ofDEFINES?and?INCLUDEPATH?into a?Defines.pri?file at the same level as the?.pro?Project file, for example:

/SomeLibrary /SomeLibrary/SomeLibrary.pro /SomeLibrary/Defines.pri

In?Defines.pri, add the?DEFINES?and?INCLUDEPATH?settings:

DEFINES?+=?SOME_COMPILER_SETTINGmessage(Including?$$_FILE_?from?$$IN_PWD) INCLUDEPATH?+=?$$IN_PWD/source

In?SomeLibrary.pro, add

include(Defines.pri)

In any other project, include the?DEFINES?and?INCLUDEPATH?settings using a similar?include:

include(/SomeLibrary/Defines.pri)

You should then see something like?"Including /SomeLibrary/Defines.pri from /SomeLibrary"?show up in the General Messages window in Qt Creator, when the project files are reparsed, meaning that the dependent project pulled in these settings properly. In this way, any changes made to the?Defines.priwill get propagated to the consuming projects.

So that’s it. Good luck.

Update

After some experimentation, you still need to “Add Library” the static library configuration blocks to the?.pro?project file of any consuming executables, for some reason when I tried moving these configuration blocks from the executable?.pro?files to the library?.pri?files,?qmake?started getting stuck in an infinite loop.

Omitting these configuration blocks will also cause the executables not to link. I don’t think I’m going to investigate this more closely, since solving the includeable?DEFINES/INCLUDEPATH?problem took care of a bigger build consistency issue. (But maybe I’ll come back to it.)

Thank you for browsing my blog

Original from?https://vilimpoc.org/blog/2014/02/21/qmake-subdirs-project-automatic-dependencies/

轉載于:https://blog.51cto.com/844133395/1795590

總結

以上是生活随笔為你收集整理的QMake Automatic Dependencies的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。