I am using qmake to cross-compile my ARM based program on Ubuntu. I have ran into the multithreading issue as described in this thread:
C++ 11 Threads, Error Pure virtual function called
One answer suggests adding the flag to the compilation as:
g++ -pthread -std=c++11 -D__GCC_HAVE_SYNC_COMPARE_AND_SWAP_{1,2,4} thread1.cpp
I am not sure how to add this -D__GCC_HAVE_SYNC_COMPARE_AND_SWAP_{1,2,4} in my qmake project file.
I did QMAKE_CXXFLAGS += -D__GCC_HAVE_SYNC_COMPARE_AND_SWAP_{1,2,4}. My error still remains so I wanted to confirm if this is the right way to add that flag.
It's a bash glob/wildcard. Expands to
-D__GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 -D__GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 -D__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4
Related
I have a c++ program, which contains two classes. one of them is using libssh and some of its functions and another one is for calculating cpu usage. there is a link of how I a built and added libssh:libssh's functions couldn't be found on qt my program works fine. now I want to build a .so library out of it to use in other programs. first I made two .o file like this:
gcc -c -fPIC info.cpp -o info.o
gcc -c -fPIC cpuusage.cpp -o cpuusage.o
and I made a .so from them:
gcc -shared -o libsmc.so info.o cpuusage.o
whenever I want to use libsmc.so, I include info.h, but the problem is that libssh functions cannot be found. I think I have to add libssh statically to my project. but I don't know how to!
Ps:I read this explanation :Using a shared library in another shared library , but this is for linking shared libraries that have been used in a program via command line, I don't wanna compile program with command line and want to link libraries constantly.
To build a C/C++ software using external libraries, I would really recommend to use a build system instead of typing commands manually.
The most used build system for C++ is CMake (https://cmake.org/), which is well supported by Qt, but there are many other build systems existing. Another is QMake, which is Qt's build system.
If you are using an IDE, like QtCreator or Microsoft Visual Studio, CMake is integrated as well. There are plenty of tutorials and example to use CMake for a project (e.g. https://mirkokiefer.com/cmake-by-example-f95eb47d45b1), even though the learning curve is not as steep as I would want.
But if you still want to use command line (or to debug the command line generated by CMake): When linking against a library, you need to:
Give the include path to the compiler, i.e. the path where the .h of the external library can be found. With gcc, this is done with -I, e.g. "-I/usr/lib/mylib/include".
Give the library folder and name to the linker, i.e. the path where to find the compiled library, as well as its name. With gcc, this is done with -L for the path and -l for the name. Check the gcc manual for more details about these commands.
And if you want to use CMake, then you can use the functions:
target_include_directories(..)
and
target_link_libraries(..)
I'm trying to use this sqlite extension to calculate stdev in Sqlite dbs, on Linux, I use this command to compile the lib
gcc -fPIC -lm -shared extension-functions.c -o libsqlitefunctions.so
but seems that the .load command is not in the sqlite .help command list, and I got error:
unknown command or invalid arguments: "load". Enter ".help" for help
Same thing happens when I use the command:
sqlite> SELECT load_extension('./libsqlitefunctions.so');
SQL error: no such function: load_extension
I tried to use this instruction to compile sqlite:
0. untar latest sqlite3 source code in a new directory
1. cd to the newly untarred sqlite directory
2. Comment out the line in Makefile.in to enable loadable extensions:
# TCC += -DSQLITE_OMIT_LOAD_EXTENSION=1
3. ./configure LIBS=-ldl && make sqlite3
4. export LD_LIBRARY_PATH="`pwd`:$LD_LIBRARY_PATH"
5. gcc -I`pwd` -shared src/test_loadext.c -o half.so
6. ./sqlite3
But couldn't find the line "TCC += -DSQLITE_OMIT_LOAD_EXTENSION=1" in the newest Sqlite source code.
It looks like configure was updated but not the documentation. Try
./configure --enable-dynamic-extensions
The reference is the configure source code. Digging further, it looks like the dynamic extensions are enabled by default. From README:
The generic installation instructions for autoconf/automake are found
in the INSTALL file.
The following SQLite specific boolean options are supported:
--enable-readline use readline in shell tool [default=yes]
--enable-threadsafe build a thread-safe library [default=yes]
--enable-dynamic-extensions support loadable extensions [default=yes]
So I think load is present. It's the second part of the error invalid arguments that's the problem.
The cause seems to be that you're using Linux instructions. That won't work. Macs don't generally have .so files, which is what your compilation command is generating.
The method of compiling and loading a Mac dynamic library, loadable as an extension, is at this location. The compile command is going to look something like
gcc -bundle -fPIC -I/path-to-sqlite/sqlite3 -o filename.sqlext filename.c
Note the -bundle and -fPIC that are important for dynamic loading, but which you were missing. The resulting filename will be filename.sqlext, so use that in your path.
It may be worth noting that you may get a "missing symbols" error when you load the library - this is due to the fact that the -lm flag needs to be at the end of the compile command thus:
gcc -fPIC -shared extension-functions.c -o libsqlitefunctions.so -lm
Regards Fat jonnie
Using glew, I'm trying to link the simple program
#include </usr/include/GL/glew.h>
int main (int argc, const char * argv[])
{
glewInit();
return 0;
}
in XCode 4, under OSX Lion, which reports the error:
ld: library not found for -lGLEW.1.7.0
Command /Developer/usr/bin/clang++ failed with exit code 1
however, the error output also reports the following flags for the linker
-mmacosx-version-min=10.7 -L/usr/lib -lGLEW.1.7.0 -lglfw -framework OpenGL -framework Cocoa
and indeed, libGLEW.1.7.0 does reside in /usr/lib
Moreover, if I try to build the program by hand, with
gcc -L/usr/lib -lGLEW.1.7.0 main.cpp
I get an a.out file without any errors reported (which if run causes a segmentation fault, but maybe that's to be expected)
Any ideas on what might be causing XCode to produce this error and how it could be avoided?
Built and installed GLEW myself and had the same issue with plain gcc inside a makefile on OS X with compilation of code from https://github.com/jckarter/hello-gl
The following steps resolved the issue:
I found my GLEW libs (libGLEW.a and libGLEW.dylib) installed in /usr/lib directory (it definitely was there owned by root with r permissions for others). Tried to change GLEW_LIB variable from the makefile to /usr/lib but still got ld: library not found for -lGLEW
after that I tried to link compiled program against static library directly (without -l flag) - for that I removed -lGLEW from gcc command and changed it to direct link t library /usr/lib/libGLEW.a - it compiled and linked fine
Ok - it's a work around to try first
Then I created two links to my libraries with the following commands:
ln -s /usr/lib/libGLEW.a /usr/local/lib/libGLEW.a
ln -s /usr/lib/libGLEW.dylib /usr/local/lib/libGLEW.dylib
and finally got it working with original makefile (only changed GLEW_LIB variable to /usr/local/lib).
Probably GLEW's make install should place libraries to /usr/local/lib directly.
(I have removed this from an edit to the question and posted it as an answer, as per leppie's suggestion)
I might have found the answer in some details I had considered unimportant in my original post. So here goes, in case others might encounter a similar problem.
Apparently, XCode4 projects use clang++ by default, which in the link phase accepts a parameter -isysroot (which apparently ld does not accept).
Now, if in your build settings (as was my case) your Base SDK has been defined as something other than Current Mac OS, the parameter -isysroot will be introduced with the value of a directory pointing to that SDK, thus (this is my guess) prepending this to all other lib directories you might be including with -L.
In my case, -L/usr/lib was effectively turning into -L/Developer/SDKs/MacOSX10.7.sdk/usr/lib which does exist and did not contain libGLEW, hence the error "library not found"
My problem is related to the one discussed here:
Is there a way that OpenMP can operate on Qt spanwed threads?
Upon trying to run my Qt-based program under Mac OS that has an OpenMP clause in a secondary thread, it crashed. After browsing through the web, now I understand that it is caused by a bug in the rather old version (4.2) of gcc supplied by Apple.
Then I downloaded the latest 4.6 version of gcc from http://hpc.sourceforge.net and tried to compile the project, but I got the following errors from g++ compiler:
unrecognized option ‘-arch’
unrecognized option ‘-Xarch_x86_64’
I learned that this is because these are options, which can be only interpreted by the custom-configured Apple-gcc compiler, but not by standard gcc.
Could anybody please help me could I overcome this issue and configure g++ 4.6 to use with Qt in order to get a bug-free OpenMP support? I admit that I'm a newbie under Mac OS platform with regard to compilers and programming and would like to port my code from Visual Studio-Qt environment.
Many thanks in advance!
If you aren't afraid of messing with your Qt installation, then change the QMAKE_CFLAGS_X86_64 entry in ~/QtSDK/Desktop/Qt/4.8.1/gcc/mkspecs/common/g++-macx.conf.
Replace ‘-Xarch_x86_64’ with ‘-arch x86_64’.
You can use your non-Apple gcc v4.6 and compile a binary for each architecture you want to build (use --target=${ARCH} should be fine for i386 and x86_64). Then once you have a binary for each of the architectures use lipo like so:
lipo -create -arch i386 binary_32bit -arch x86_64 binary_64bit -output binary_universal
This will create a fat binary (aka universal binary) named binary_universal from binary_32bit and binary_64bit.
Or you could use clang/llvm instead of gcc, which probably won't have the bug you described and (if supplied via Apple's developer tools) should be able to compile universal binaries directly.
You should run qmake woth corresponding -spec option, for example, to use gcc46 on freebsd it is needed to run qmake so:
qmake --spec=freebsd-g++46
Lipo can indeed be used to put multiple object files together into a "fat" object file, in fact it turns out this is just what apple's compiler does. Their GCC compiler is actually a driver that maps various architectures to the appropriate compiler for the architecture and then mashes the objects together using lipo.
see: http://lists.macosforge.org/pipermail/macports-dev/2011-September/016210.html
Here is the source file for that driver:
http://opensource.apple.com/source/gcc/gcc-5666.3/driverdriver.c
All one needs to do to get a new version of GCC to honor the -arch flag is to modify this driver and get it to point to a script wrapper for your version of gcc that adds the appropriate flags for the given architecture and then passes all the rest of the arguments. Something like this:
#!/bin/sh
/opt/local/bin/gcc-mp-4.6 -m32 $#
and
#!/bin/sh
/opt/local/bin/gcc-mp-4.6 -m64 $#
Here is a link that talks about how to do it, and provides a cmake project to easily get the macports version of GCC fixed up and supporting the -arch flag for the two intel architectures:
http://thecoderslife.blogspot.com/2015/07/building-with-gcc-46-and-xcode-4.html
After I successfully implemented my first JVMTI agent and the building completes with the g++ compiler I want to go over integrate the building process into my Qt project.
However I am facing some build process configuration issues:
The parameters I would run with the g++ compiler looks like this:
g++ -fPIC -shared agent.cpp -o libagent.so -I /usr/lib/jvm/java-6-openjdk/include -I /usr/lib/jvm/java-6-openjdk/include/linux
This works very well. Now to qmake:
I am aware of the parameter CXXFLAGS to add further parameters to the C++ compiler used by qmake, but how can I convert this parametrized compiler call into qmake?
With the help of Qt Undocumented qmake I figured out a custom configuration in qmake. However, it is not flawless, it produces now a libagent.so and a agent.o which is not needed.
SOURCES_AGENT = agent.cpp
agent.name = agent
agent.input = SOURCES_AGENT
agent.dependency_type = TYPE_C
agent.variable_out = OBJECTS
agent.output = libagent.so
agent.commands = $${QMAKE_CXX} $(CXXFLAGS) -fPIC -shared -o libagent.so $(INCPATH) ${QMAKE_FILE_IN}
QMAKE_EXTRA_COMPILERS += agent
I don't know the specific answer but...
As JVMTI agents are "usually" headless are you using qmake because your project has a head that you are developing in kdevelop/qtcreator? Is the head using the attach API?
If not and it is purely headless then would not a different editor/cmake be better? qmake is now a preproc for cmake, for the MOC stuff, no?
I must admit I'm a bit fuzzy on q/cmake although I'm hoping to move to cmake for my work.