gcc linker can't find library - c++

I get a strange error while building my Qt C++ project on Ubuntu Linux using GCC 5.2.1:
/usr/bin/ld: cannot find -llibmath
I include external dynamic library to maky qmake project using command:
LIBS += -L/home/rem -llibmath
and I have library file at path /home/rem/libmath.so
As I can see from compiler output:
g++ -Wl,-rpath,/home/rem/Qt/5.5/gcc_64 -Wl,-rpath,/home/rem/Qt/5.5/gcc_64/lib -o Bazis main.o builder.o -L/home/rem -llibmath -L/home/rem/Qt/5.5/gcc_64/lib -lQt5OpenGL -L/usr/lib64 -lQt5QuickWidgets -lQt5Widgets -lQt5Quick -lQt5Gui -lQt5Sql -lQt5Test -lQt5Qml -lQt5Network -lQt5Core -lGL -lpthread
all parameters are correctly send by qmake to g++.
What is the source of my problem?

The solution is simple:
I changed my .pro file from:
LIBS += -L/home/rem -llibmath
to:
LIBS += -L/home/rem -lmath

Related

MSYS2 and libcurl, which libs to link?

I am having some big headaches linking statically libcurl in MSYS2 mingw.
I installed libcurl and all the listed dependencies from here
https://packages.msys2.org/package/mingw-w64-x86_64-curl
Since I am using CodeBlocks as IDE I need to supply a whole list of libs in form of lib#?.a, please keep in mind that I know nothing of Linux world and gcc tools and command line, otherwise I wouldn't be using an IDE!
Also I am not skilled enough to compile lib packages. I just need to write some portable code to do a https post request in cpp, so I need libcurl.
Can you tell me a complete list of all the needed libs to link against ? I tried all my best but I keep getting an infinity of unresolved symbols
UPDATE
After having checked what the package config for libcurl says, I have installed all the missing libs and used the following command line:
g++.exe -o MyProg.exe obj\Release\main.o -static-libstdc++ -static-libgcc -static -m64 -lcurl -lnghttp2 -lidn2 -lssh2 -lpsl -ladvapi32 -lcrypt32 -lssl -lcrypto -lssl -lcrypto -lgdi32 -lwldap32 -lzstd -lbrotlidec -lz -lws2_32 -s
Despite that I am still getting tons of undefined references:
d:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/10.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: d:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/10.2.0/../../../../x86_64-w64-mingw32/lib/../lib\libcurl.a(gsasl.o):(.text+0x14): undefined reference to `gsasl_init'
[plus many other 'gsasl...' referrences]
d:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/10.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: d:/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/10.2.0/../../../../lib\libbrotlidec.a(decode.c.o):(.text+0x2d28): undefined reference to `BrotliTransformDictionaryWord'
[plus many other 'brotli...' references]
pkg-config will tell you the necessary flags. Install it from the package mingw-w64-x86_64-pkg-config.
Run it as pkg-config --libs --static libcurl.
Copy the output into "linker flags -> other". For me the output is -L/mingw64/lib -lcurl -lnghttp2 -lidn2 -lssh2 -lpsl -ladvapi32 -lcrypt32 -lssl -lcrypto -lssl -lcrypto -lgdi32 -lwldap32 -lzstd -lbrotlidec -lz -lws2_32. Don't forget to add the --static flag, if you're not already doing so.

How to embed glut library into c++ project?

I have a c++ project but when distribute this, need install libglut.so.3.:
./bin: error while loading shared libraries: libglut.so.3: cannot open shared object file: No such file or directory
I want the user not to have to install this dependency. How to embed the library into project?
I try compile as static library in c++ project using g++. My make file contains:
#g++ \
-o bin \
-std=c++11 \
main.cpp \
-lm -lGL -lGLU -lglut \
;
I try define glut as static library:
-lm -lGL -lGLU -Wl,-Bstatic -lglut -Wl,-Bdynamic
But the compiler says:
/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libglut.a(libglut_la-freeglut_state.o): undefined reference to symbol 'XGetWindowAttributes'
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/libX11.so: error adding symbols: DSO missing from command line
I try download freeglut-3.0.0 and compile as static library:
Change CMakeLists.txt file for static compile:
OPTION(FREEGLUT_BUILD_SHARED_LIBS "Build FreeGLUT shared library." OFF)
OPTION(FREEGLUT_BUILD_STATIC_LIBS "Build FreeGLUT static library." ON)
And in the CMakeCache.txt:
//Build FreeGLUT shared library.
FREEGLUT_BUILD_SHARED_LIBS:BOOL=OFF
//Build FreeGLUT static library.
FREEGLUT_BUILD_STATIC_LIBS:BOOL=ON
And compile it:
$ cmake .
$ make
[ 62%] Built target freeglut_static
...
[100%] Built target shapes_static
And verify:
$ ll lib/libglut.a
-rw-r--r-- 1 me me 690860 nov 17 19:11 lib/libglut.a
$ file lib/libglut.a
lib/libglut.a: current ar archive
Now, change the makefile:
-lm -lGL -lGLU freeglut-3.0.0/lib/libglut.a
And compile:
$ make
usr/bin/ld: freeglut-3.0.0/lib/libglut.a(fg_state_x11.c.o): undefined reference to symbol 'XGetWindowAttributes'
//usr/lib/x86_64-linux-gnu/libX11.so.6: error adding symbols: DSO missing from command line
But, same error message.
In similar problem: fglut/libfglut.a(freeglut_state.o): undefined reference to symbol 'XGetWindowAttributes' , i try add x11 libraries into project:
-lm -lGL -lGLU -lX11 freeglut-3.0.0/lib/libglut.a
Or:
-lm -lGL -lGLU -lX11 -Wl,-Bstatic -lglut -Wl,-Bdynamic
But have a same error message. What happened?
I have successfully linked my a GLUT program using this command
g++ -o ogl-test main.cpp freeglut-3.0.0/lib/libglut.a -lGL -lGLU -lX11 -lXxf86vm -lXext -lXrandr -lXt -lXi
Hopefully this will also work for you. Make sure you change the path to glut library.

How I can include OpenSSL in my Qt program on Linux?

In my Qt program I have to convert a string to a hash. I want to use OpenSSL on Debian. Little brief of my code:
#include <openssl/sha.h>
...
unsigned char data[] = "data to hash";
unsigned char hash[SHA512_DIGEST_LENGTH];
SHA512(data, sizeof(data) - 1, hash);
I have installed openssl and libssl-dev. And I also have changed my .pro document, looks like that:
TEMPLATE = app
QT = core gui
HEADERS += window.h
PKGCONFIG += openssl //found in another solution, but it does not work
LIBS += -L/usr/share/doc libssl-dev
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
SOURCES += main.cpp window.cpp
In LIBS I have tried all possible locations that I get with sudo dpkg -L libssl-dev . Does anyone what I am missing? It doesn't compile and I sure is about that.
Thanks.
Here is the error when linking:
/usr/lib/x86_64-linux-gnu/qt4/bin/qmake -o Makefile App.pro
g++ -m64 -Wl,-O1 -o App main.o window.o moc_window.o -L/usr/lib/x86_64-linux-gnu -L/usr/share/doc/libssl-dev -libssl-dev -lQtGui -lQtCore -lpthread
/usr/bin/ld: cannot find -libssl-dev
collect2: error: ld returned 1 exit status
Makefile:105: recipe for target 'App' failed
make: *** [App] Error 1
In general if the library is libsomelib.so you must import it using -lsomelib, and in your case assuming that you have installed it using the system's tools it is not necessary to pass it a path, just add the following since the library is libssl.so:
LIBS += -lssl -lcrypto
or you can also use pkg-config:
PKGCONFIG += libssl
where /usr/lib/pkgconfig/libssl.pc is:
prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include
Name: OpenSSL-libssl
Description: Secure Sockets Layer and cryptography libraries
Version: 1.1.0g
Requires.private: libcrypto
Libs: -L${libdir} -lssl
Libs.private: -ldl
Cflags: -I${includedir}

Linking QX11Info

I'm porting an application qt3 -> qt5. As part of that I have in a .cpp file changed (Qt3)
mySystemstruct.display = theWidget->x11Display();
into (Qt5)
mySystemstruct.display = QX11Info::display();
Include has been added in the file.
#include <QX11Info>
I am not using Qt Creator. The file in question is not been linked using qmake. (other files has)
I get this link errors:
/home/go/NetBeansProjects/Arbete_216/Ajourwork/Components/TheRealDeal/GUI/linuxobj//GO_C_QtGUI.o: In function `GO_C_QtGUI::initHistoryFilm(QWidget*, int, int)':
/home/go/NetBeansProjects/Arbete_216/Ajourwork/Modules/GUI/QtGUI/GO_C_QtGUI.cpp:668: undefined reference to `QX11Info::display()'
using this compile command:
clang++ -o gvs_GUI linuxobj/*.o linuxobj/libQtSpecific.a -DLINUX -I/include/ -g -I /opt/intel/composer_xe_2015.1.133/ipp/include/ -Wno-deprecated -D_GNU_SOURCE -D_REENTRANT -D__STDC_CONSTANT_MACROS -I/usr/include/postgresql/ -I/usr/local/Qt/5.2.1/gcc_64/include/QtX11Extras/ -I/usr/local/Qt/5.2.1/gcc_64/include/QtWidgets/ -I/usr/local/Qt/5.2.1/gcc_64/include/ -I/usr/local/Qt/5.2.1/gcc_64/include/QtGui/ -fPIC -fPIE -I/home/go/ffmpeg_build/include/ -I/usr/local/Qt/5.2.1/gcc_64/include/QtCore/ -fPIC -fPIE -I/home/go/ffmpeg_build/include/libavcodec -I/home/go/ffmpeg_build/include/libavformat/ -lpq -lippi -lipps -lippcore -lpthread -lgcrypt -lippvm -lippcv -lippcc -L/opt/intel/composer_xe_2015.1.133/ipp/lib/intel64 -L/usr/local/Qt/5.2.1/gcc_64/lib/ -L/usr/X11R6/lib/ -lXv -lX11 -lXext -ltar -lavformat -lavcodec -lavfilter
Is it not possible to build using Qt libs not using qmake? My code has been built that way with earlier versions of Qt so it seems it should work.(?)
Since not using qmake for linking, I use -I/usr/local/Qt/5.2.1/gcc_64/include/QtX11Extras/ -L/usr/local/Qt/5.2.1/gcc_64/lib/ but it doesn't seem to work.
The QtX11-lib seems to be in place:
locate libQt5X11Extras.so
/usr/local/Qt/5.2.1/gcc_64/lib/libQt5X11Extras.so
/usr/local/Qt/5.2.1/gcc_64/lib/libQt5X11Extras.so.5
/usr/local/Qt/5.2.1/gcc_64/lib/libQt5X11Extras.so.5.2
/usr/local/Qt/5.2.1/gcc_64/lib/libQt5X11Extras.so.5.2.1
What am I doing wrong here?
-L/usr/local/Qt/5.2.1/gcc_64/lib/ only tells the linker where to find the libraries.
You must then add -lQt5X11Extras to ask to link to the Qt5X11 library.

qmake doesn't add libraries from .pro file to the makefile

I try to build an QT project using qmake. For this I need the boost library.
LIBS += -L/usr/lib/ \
-lboost_system \
-lboost_filesystem
But after running qmake, these libraries are not added to the makefile:
LIBS = $(SUBLIBS) -L/usr/X11R6/lib64 -lQt5MultimediaWidgets
-L/build/buildd/qtmultimedia-opensource-src-5.0.1/lib -L/usr/lib/x86_64-linux-gnu
-L/usr/lib/x86_64-linux-gnu/x86_64-linux-gnu -lQt5OpenGL -lQt5Multimedia -lpulse
-lQt5Widgets -lQt5Network -lQt5Gui -lQt5Core -lGL -lpthread
As expected, the linker prints many error like
/usr/include/boost/system/error_code.hpp:214: error: undefined reference to boost::system::generic_category()
If you want to take a look to the whole .pro file, go to https://raw.github.com/francisengelmann/FabScan100/master/qtTest/qtTest.pro
I am also having a similar problem with opencv. Does anyone know how to solve this issue ?
You need to run qmake again after changing the .pro file. Just removing your build directory is not enough.
Also are you sure your qmake target is linux-g++? Does the INCLUDEPATH work?