How to force include a header file

[rawfool]

I have a header file viz., customTypes.h and I need to force include like in Visual Studio.
In Visual Studio there is a option in settings, called "Force Include" where we select the file, which does this to to the compiler settings -

/FI"customTypes.h"

/FI"customTypes.h"

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Now if I'm using that header file from the path, it's linking me to the file while typying #include "customTypes.h", but on compilation, it's giving some type errors.
Kindly help me how to do this in Qt. Thank you.

[ChrisW67]

Assuming you are still using the Microsoft compiler then you do it by arranging for exactly the same command line switch. Something like:

QMAKE_CXXFLAGS +=     /FI"customTypes.h"

QMAKE_CXXFLAGS +=     /FI"customTypes.h"

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I don't know why this would be useful though.

[rawfool]

I'm using MinGW 4.7 and when I do QMAKE_CXXFLAGS += /FI"customTypes.h", it's saying, error: No such file or directory.
But I've included that header file path in INCLUDEPATH.
What do I do now? Thank you for the reply.

[wysota]

I don't think GCC supports forced include, whatever that is. If you want a file included in your source code then include it there so that people reading your code can learn the file gets included instead of having to analyze crypting compiler invokations.

[ChrisW67]

I'm using MinGW 4.7 and when I do QMAKE_CXXFLAGS += /FI"customTypes.h", it's saying, error: No such file or directory.
But I've included that header file path in INCLUDEPATH.
What do I do now? Thank you for the reply.

It may have helped to have mentioned that you were not using the Microsoft compiler. As it stands at the moment the compiler is probably complaining because there is no file called literally '/FI"customtypes.h"': even cursory inspection of existing command lines or the manual would have highlighted that "/" does not introduce a command line switch to GCC.

GCC has an equivalent switch that can be found with less than three minutes and the GCC manual:

-include "someobscurefilethatisboundtobelost.h"

-include "someobscurefilethatisboundtobelost.h"

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Make sure read about where the compiler will be looking for someobscurefilethatisboundtobelost.h.

The correct approach is to fix your source code, not to try and fudge it with obscure compiler options.

[rawfool]

My customTypes.h file is in C:/svn/trunk/vtd-xml, how do I force include ?
I tried each of the following ways in my .pro file, but it's giving error

-include "customTypes.h"
INCLUDEPATH += <some/path> \
                            C:/svn/trunk/vtd-xml

-include "customTypes.h"
INCLUDEPATH += <some/path> \
                            C:/svn/trunk/vtd-xml

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-include "C:/svn/trunk/vtd-xml/customTypes.h"

-include "C:/svn/trunk/vtd-xml/customTypes.h"

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// Without quotes
-include C:/svn/trunk/vtd-xml/customTypes.h

// Without quotes
-include C:/svn/trunk/vtd-xml/customTypes.h

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-include -I"C:/svn/trunk/vtd-xml/customTypes.h"

-include -I"C:/svn/trunk/vtd-xml/customTypes.h"

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All the attempts giving -

Extra characters after test expression.
[Makefile] Error 3

Extra characters after test expression.
[Makefile] Error 3

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[wysota]

QMAKE_CXXFLAGS += "-include ..."

[rawfool]

Thank you Wysota for the reply.
I did that it's almost working, still I need some more clarifications regd., this.
The file C:/svn/trunk/vtd-xml/customTypes.h is being used by any other files and those needs to be specified. I tried including all those files below mentioned way. But no luck. kindly help me.

QMAKE_CXXFLAGS += "-include C:/svn/trunk/vtd-xml/customTypes.h C:/svn/trunk/vtd-xml/arrayList.h C:/svn/trunk/vtd-xml/autoPilot.h C:/svn/trunk/vtd-xml/binaryExpr.h C:/svn/trunk/vtd-xml/bookMark.h C:/svn/trunk/vtd-xml/cachedExpr.h ...(many other files separated by space)"

QMAKE_CXXFLAGS += "-include C:/svn/trunk/vtd-xml/customTypes.h C:/svn/trunk/vtd-xml/arrayList.h C:/svn/trunk/vtd-xml/autoPilot.h C:/svn/trunk/vtd-xml/binaryExpr.h C:/svn/trunk/vtd-xml/bookMark.h C:/svn/trunk/vtd-xml/cachedExpr.h ...(many other files separated by space)"

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error: fatal error: cannot specify -o with -c, -S or -E with multiple files

error: fatal error: cannot specify -o with -c, -S or -E with multiple files

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The files other than customTypes.h need not be force included, but just included because, customTypes.h file is being used by all the other files (and the files are in that specified directory).

[wysota]

This is not a GCC usage kindergarden. Read the manual. Or better yet fix your code to avoid using forced includes.

[ChrisW67]

The GCC "-include" option, as the manual clearly indicates, takes a single file name as an argument.

If the customTypes.h is already "being used by any other files" then I fail to see why a forced included is required. If the "any other files" contained the line:

#include "customTypes.h"

#include "customTypes.h"

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you would not have the problem you have made for yourself.

[rawfool]

I'm force including customTypes.h file which is part of other process developed using Visual C++. Also the files that are including customTypes.h file are part of that process.
I'm trying to load a DLL that parses a huge xml file. That parser DLL is created by other team and they use Visual C++ for development. So that's the reason I'm left with only option of force including the required files for using required DLL APIs.
Thank you.

[wysota]

That's not true. If you physically have the file there and its presence is mandatory for the compilation to work then you can as well include the file directly in your files. Using your currrent approach only obscures your source code making it more error prone and more difficult to manage. If the other team provides a library you have to use, then just use it.