Moc issue with osX/iOs application

SGaist

Well, you don't need them since Qt already provides defines for the platform it supports so you only have to use

#if defined(Q_OS_MACOS)
#elif defined(Q_OS_IOS)
#endif

NAnder

I have tried, but I have the same issue with moc in qmake if I use Q_OS_MACOS and Q_OS_IOS : moc only use the code where Q_OS_MACOS is define whatever I ask it to build, an iOs project or an OsX project.

All my class depending of #if defined(Q_OS_IOS) got the warning message :

Note: No relevant classes found. No output generated.

Is it the normal qmake/moc behaviour or I do something bad ?

SGaist

Can you post the code that triggers that ?

NAnder

Hi, sorry for the late answer. I got some issues.
Here is smallest set of code to sample that show the problem:
project.pro

QT       += core gui

TARGET = Bugs
TEMPLATE = app

SOURCES += main.cxx
HEADERS += test_ios.hxx test_osx.hxx

main.cxx

#include <QApplication>
#include "test_ios.hxx"
#include "test_osx.hxx"

Tests::Tests() {}
Tests::~Tests() {}
//#include <TargetConditionals.h>
#ifdef Q_OS_IOS
//#if TARGET_OS_SIMULATOR || TARGET_OS_IPHONE
void Tests::Hello() {}
#endif

int main(int argc, char * argv[])
{
  Tests bug;
  return 0;
}

test_ios.hxx

#include <QApplication>
#ifdef __APPLE__
//# include <TargetConditionals.h>
//# if TARGET_OS_SIMULATOR || TARGET_OS_IPHONE
#  ifdef Q_OS_IOS

#  include <QObject>

class Tests : public QObject
{
  Q_OBJECT

public:
  explicit Tests();
  ~Tests();

  void Hello();
};

# endif
#endif

test_osx.hxx

#include <QApplication>
#ifdef __APPLE__
# include <TargetConditionals.h>
//# if TARGET_OS_OSX
#ifdef Q_OS_MACOS

#  include <QObject>

class Tests : public QObject
{
  Q_OBJECT

public:
  explicit Tests();
  ~Tests();
};

# endif
#endif

I create the Xcode project with :

Qt5.9.1/5.9.1/ios/bin/qmake ../project.pro

Best regards

kshegunov

You're running moc on an empty header (either one of the two is, or both are, empty). So moc complains about not having any class to parse.

NAnder

Hi, thx for your answer.
Yes it should complain about one empty header, that would not be an issue.
But it complain about the wrong one, when i try compile for iOs, why it say :

Note: No relevant classes found. No output generated.

about test_ios.hxx

kshegunov

My guess would be that __APPLE__ isn't defined.

SGaist

Rather than having empty headers, just don't try to build that class if it doesn't make sense on a given platform.

Use scopes in your .pro file to only compile what is needed.

NAnder

Hi, thx for the answer.

__ APPLE__ is defined otherwise test_osx.hxx would generate an empty moc file too, which is not the case.

Yes using scope in .pro file is the way to avoid useless warning, but I not used it here because I wanted to show that moc only generate a moc file from test_osx.hxx whatever I ask qmake to generate a project for OsX or iOs.

My question is it the normal moc behaviour to expand only OSX macro when I ask qmake to generate a project for iOs ? If not, why it do it with my sample ?

Best regards,

SGaist

For me it generates an empty moc file also for iOS when building for macOS and that's expected. Since you are passing both files to the HEADERS variable moc will be run on both generating an empty file for the other OS since the macro is correctly handled.

To have a truly cross-platform code base, use scopes in your .pro file and only include what's relevant to the platform in your source code otherwise it will become quiet quickly a nightmare to maintain.

NAnder

Hi,

Thank you for the answers.

It took me sometime for write back, because i was training my english to be able to answer here. My question is very clear in my head, but it seems my words are bad.

Yes it's generate an empty moc class warning when i compile for mac osX. This is not an issue, first it just a warning, the compilation still go on, and like you said fix the warning is very easy.

My question was, why it not work when i try compile for iOS. When i try, I got a warning about test_ios.hxx generating an empty file. And that is a critical error because the compiler will not be able to find the iOS code. Moc seems not expand IOS macro, but always OSX macro whenever it's an OSx or IOs build.

Best regards,

SGaist

Can you check whether it's still the case with more recent version of Qt ?

NAnder

Thank a lot for the answer.
I'll try as soon I can.