[Development] Qt API review with clazy

Mathias Hasselmann mathias at taschenorakel.de
Mon Sep 12 09:06:40 CEST 2016

Just that the approach of clang-tidy is fundamentally wrong:

You simply don't do static checks as a after thought, at random times 
when sun, mars and moon are in proper constellation.

Why? Because when running this checks occasionally too much cruft will 
have accumulated that it is worth and reasonable to fix those issues: 
Too big chunk of boring and still expensive work. Too big risk to 
introduce regressions.

You really want to make this checks part of your daily development 
experience, you want the compiler to tell you about your mistakes as 
soon as you compile that code for the first time. It's much easier to 
fix your mistakes if you just wrote them. It's much safer to fix them 
before even doing the first tests. Well, and you'll learn much earlier 
about possible anti-patterns, so you'll write less of such code.

I hear you saying "but you could add clang-tidy" to your build scripts, 
but that's not a valid argument adding the following flags is considered 
too much effort already:

   -Xclang -load -Xclang ClangLazy.so -Xclang -add-plugin -Xclang clang-lazy


Disclaimer: I am working with Sergio and using his awesome plugin since 
its very first days.

Am 12.09.2016 um 08:38 schrieb Ch'Gans:
> On 12 September 2016 at 10:34, Sergio Martins <sergio.martins at kdab.com> wrote:
>> On Sunday, 11 September 2016 21:43:46 WEST Jérémie Delaitre wrote:
>>> Can the same checks be implemented in clang-tidy instead of having yet
>>> another tool? clang-tidy now has boost specific checks so maybe they would
>>> also accept a Qt specific module in there.
>> I haven't been able to use clang-tidy on big qmake projects such as Qt, it
>> either crashes or stops with "include not found" errors. It also requires an
>> intermediate step, where you generate a "compiler command database" file with
>> yet another tool [1]
> Both CMake (since 2.8.5, see [1]) and Qbs (master branch) can generate
> this "compiler command database".
> Maybe your tool could be made to work with this DB (via clang-tidy)
> and as a clang plugin.
> The DB approach has the added advantage that it doesn't require
> modifying CXX flags, which can be a problem on projects that have
> "buggy" build files.
> Having your checks run by clang-tidy would also definitely widen your user base.
> clang-tidy have specific rules for LLVM, boost, google, ... Would be
> nice to add Qt.
> Chris
> [1] http://clang.llvm.org/docs/JSONCompilationDatabase.html#supported-systems
>> clazy, otoh, is a compiler plugin, it integrates with your normal compilation
>> run, you don't have to run any more tools after doing "make" as you usually
>> do.
>> Enabling clazy is just a matter of modifying your CXX flags,  which you can
>> easily do with qmake or mkspec. Or ENABLE_CLAZY in CMake if you're building
>> KDE.
>> [1] https://github.com/rizsotto/Bear
>> Regards,
>> --
>> Sérgio Martins | sergio.martins at kdab.com | Senior Software Engineer
>> Klarälvdalens Datakonsult AB, a KDAB Group company
>> Tel: Sweden (HQ) +46-563-540090, USA +1-866-777-KDAB(5322)
>> KDAB - The Qt Experts
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