[SOLVED] QT and boost : cannot find -llibboost_filesystem...

[zarachbaal]

Hi,

I work with (and I cannot an other version of Qt) :

• QT Creator 2.4.1 and QT 4.8.4 (with Mingw compiler)
• boost 1.52

To build boost :

• i first added "C:/Qt/qtcreator-2.4.1/mingw/bin" to my PATH variable
• then opened a command prompt
• went to "C:/boost_1_52"
• typed "bootstrap.bat mingw"
• and then "b2 toolset=gcc build-type=complete stage" (this took a long time (about 2h))

I would like to use QT creator with the boost library but I come up against difficulties.
My project is very simple, it's only basic QT code :

QCoreApplication a(argc, argv) 
return a.exec()

I just added some includes :

#include <boost/thread.hpp>
#include <boost/property_tree/json_parser.hpp> 
#include <boost/asio.hpp>
#include <boost/thread.hpp>

In my .pro file I have added :

INCLUDEPATH += C:/boost_1_52
LIBS += -L$quote(C:/boost_1_52/stage/lib) \
-llibboost_filesystem-mgw48-mt-d-1_52 \
-llibboost_system-mgw48-mt-d-1_52

When I run qmake and then try to build my project it fails with the error

cannot find -llibboost_filesystem-mgw48-mt-d-1_52
collect2: ld returned 1 exit status

I tried to replace "-llibboost_filesystem..." with "-lboost_filesystem..." but it does the same.

I checked and I have got these to files in the C:/boost_1_52/stage/lib
(actually I have 3 "libboost_filesystem-mgw48-mt-d-1_52" : one .a, one .dll and one .dll.a) (it's the same for "libbost_system-mgw48-mt-d-1_52")

If I remove the "-llibboost_filesystem..." and "-llibboost_system..." I've got multiple errors like

"undefined reference to WSAStartup@8"
"undefined reference to boost::system::generic_category()"

Thank you in advance for your help.

[cybercatalyst]

On a general note, I would always discourage the simultaneous usage of boost and Qt. It makes the code inconsistent, boost in general is more error-prone than the corresponding Qt classes and it is duplicating functionality. Qt is an application development framework, not a GUI library.

While it is technically possible, it is really awkward in design. Many beginners make that mistake.

[zarachbaal]

Unfortunately I am working on a project that has been started by someone else and so I have no choice but using Qt and Boost.

I forgot to say that when I built boost, it said
"failed updating 32 targets"
"skipped 64 targets
"updated 4599 targets"

I do not know if this is normal or not

[sneubert]

Hi zarachbaal,

for your includes

#include <boost/thread.hpp>
#include <boost/property_tree/json_parser.hpp> 
#include <boost/asio.hpp>
#include <boost/thread.hpp> 

you dont need boost_filesystem. Asio generates the errors.

"undefined reference to WSAStartup@8"
"undefined reference to boost::system::generic_category()"

Asio needs to be link against to additional libraries. Add to your LIBS +=
1.) Boost_system: -LC:/path/to/boost/libs and -llibboost_system-mgw48-mt-1_52
2.) On Windows, WS2_32.lib: -LC:/path/to/winsock2/lib and -lWS2_32

This is tested with boost 1_57 and mingw49 on my win7 system.
Hope it helps.

[zarachbaal]

The errors about WSAStartup@8, WSACleanup@0... disappeared, that's a start !

But I still have a bunch of undefined reference errors.
A lot have "thread" in their name like :

undefined reference to `_imp___ZN5boost6threadC1Ev'
undefined reference to `_imp___ZN5boost6thread4joinEv'

So I guess I also have to add the 'libboost_thread-mgw48-mt-1_52' library ?
But I only have '.a' files in 'stage/lib' (no '.dll" or '.dll.a' files), and if I do '-llibbost_thread-mgw48-mt-1_52' it says it cannot find the library
Maybe the lack of '.dll' and '.dll.a' is due to the 'failed updating 32 targets' when I built boost ?

Also, I still have some
undefined reference to boost::system::generic_category()
undefined reference to boost::system::system_category()

[sneubert]

I forgot to say, that I had to reorder the header includes to get a build.

#include <boost/asio.hpp>
#include <boost/property_tree/json_parser.hpp>
#include <boost/thread.hpp>

[cybercatalyst]

I can only suggest you talk with the one introducing boost (if you have to) and see whether you can get rid of it for obvious reasons. You will save yourself a lot of unnecessary work. Before trying that, I wouldn't investigate too much, this is lost time.

Other than that, I am out here.

[sneubert]

@cybercatalyst
I agree, but this wont solve the problem.

[cybercatalyst]

It does solve the problem, because you the errors you see are linker errors caused by boost. If you just stick to the Qt classes like intended, you will not have those.

[SGaist]

@zarachbaal said:

undefined reference to `_imp___ZN5boost6threadC1Ev

Hi,

You're not linking to the boost_thread library.

You missing something like:
LIBS += -lboost_thread-mgw48-mt-1_52
or similar

[zarachbaal]

@cybercatalyst :

In fact I'm using the EyeTribe eye tracking device and the SDK uses the boost library.
So I have no choice but using it.

[cybercatalyst]

No offense, but in that case you should contact their support instead asking here. I hope you understand, this is not something the community could/should help you with as the source of problems clearly is the usage of boost.

(in the sense to make them aware of their fault, you should request them to fix it)

[sneubert]

@cybercatalyst

Using boost and qt together is not uncommon. There are indeed some libraries in boost that have no equivalent replacement in qt. Sure this seems not to be a qt issue, but if you do not want to help, just leave it. I for one, as part of the community saved a lot of time looking at posts like this. And by the way the valuable answers have never been something like "dont do that" or "ask someone else".

[zarachbaal]

@SGaist :

I added "-lboost_thread-mgw48-mt-1_52" at the end of my "LIBS +=..." line.
It finds the library but I still have those errors...

I also changed the order of my includes as sneubert suggested but that did not help

@cybercatalyst :

I will contact them about this but I have to make it work on Qt for the next week...

[cybercatalyst]

@sneubert said:

Using boost and qt together is not uncommon.

Yes, you are right! And it's the source for a whole bunch of unnecessary issues. That's why I find it important to state it's the wrong way to go. The fact that boost and qt are being used side-by-side comes from the misconception that people want to somehow get rid of Qt on non-GUI code in lower level stuff because Qt is GUI-only. This is very bad and it's important to remind that Qt is an application framework.

This is the only reason I am writing this and if it makes people to rethink then this has been very useful imo.

[SGaist]

Did you check that the library name is correct ? I've based it on the ones you're already using so I might have missed something

[zarachbaal]

@SGaist :

Yes I checked and the library is here, i even copy/pasted the name to be sure
Qt does find the library, if I enter a wrong library name it gives an error (error : cannot find "false_library_name")

As I said before I only have "libboost_thread-mgw48-mt-1_52.a" file.
When I had '.a', '.dll' and '.dll.a' files for "libboost_system..."

Maybe it has something to do about it ?

[SGaist]

You can try adding DEFINES += BOOST_THREAD_USE_LIB

[zarachbaal]

@SGaist :

I just added your code, unfortunately it has no effect on the errors.

[sneubert]

I checked my boost lib dir and I do have a libboost_thread-mgw... .dll and .lib so maybe you investigate the build of the boost libraries.