I knew in the latest Linux, there is no direct linkage to math.h for c math library. so, to make it work there is requirement to add linker flag -lm . for example $ gcc count.c -lm
But in Atom Editor I am using "gpp-compiler 3.0.7" and in the settings > C Compiler there is "gcc" compiler and it works fine without "math.h" library related operations. How to and where to put
-lm linking flag to make gcc avail to link "math.h" library ?
Note: " settings > C Compiler > Default: gcc -lm" doesn't work.
Thanks a lot in advance
I found the solution, in gpp-cmpiler settings in "C Compiler options" , simply add -lm.
same for the c++ compiler Options too.
For C
Settings > C Compiler Options > (write) -lm
for C++
Settings > C++ Compiler Options > (write) -lm
Related
I'm trying to use packages that require Rcpp in R on my M1 Mac, which I was never able to get up and running after purchasing this computer. I updated it to Monterey in the hope that this would fix some installation issues but it hasn't. I tried running the Rcpp check from this page but I get the following error:
> Rcpp::sourceCpp("~/github/helloworld.cpp")
ld: warning: directory not found for option '-L/opt/R/arm64/gfortran/lib/gcc/aarch64-apple-darwin20.2.0/11.0.0'
ld: warning: directory not found for option '-L/opt/R/arm64/gfortran/lib'
ld: library not found for -lgfortran
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [sourceCpp_4.so] Error 1
clang++ -arch arm64 -std=gnu++14 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I../inst/include -I"/Library/Frameworks/R.framework/Versions/4.1-arm64/Resources/library/Rcpp/include" -I"/Library/Frameworks/R.framework/Versions/4.1-arm64/Resources/library/RcppArmadillo/include" -I"/Users/afredston/github" -I/opt/R/arm64/include -fPIC -falign-functions=64 -Wall -g -O2 -c helloworld.cpp -o helloworld.o
clang++ -arch arm64 -std=gnu++14 -dynamiclib -Wl,-headerpad_max_install_names -undefined dynamic_lookup -single_module -multiply_defined suppress -L/Library/Frameworks/R.framework/Resources/lib -L/opt/R/arm64/lib -o sourceCpp_4.so helloworld.o -L/Library/Frameworks/R.framework/Resources/lib -lRlapack -L/Library/Frameworks/R.framework/Resources/lib -lRblas -L/opt/R/arm64/gfortran/lib/gcc/aarch64-apple-darwin20.2.0/11.0.0 -L/opt/R/arm64/gfortran/lib -lgfortran -lemutls_w -lm -F/Library/Frameworks/R.framework/.. -framework R -Wl,-framework -Wl,CoreFoundation
Error in Rcpp::sourceCpp("~/github/helloworld.cpp") :
Error 1 occurred building shared library.
I get that it can't "find" gfortran. I installed this release of gfortran for Monterey. When I type which gfortran into Terminal, it returns /opt/homebrew/bin/gfortran. (Maybe this version of gfortran requires Xcode tools that are too new—it says something about 13.2 and when I run clang --version it says 13.0—but I don't see another release of gfortran for Monterey?)
I also appended /opt/homebrew/bin: to PATH in R so it looks like this now:
> Sys.getenv("PATH")
[1] "/opt/homebrew/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/Library/TeX/texbin:/Applications/RStudio.app/Contents/MacOS/postback"
Other things I checked:
Xcode command line tools is installed (which clang returns /usr/bin/clang).
Files ~/.R/Makevars and ~/.Renviron don't exist.
Here's my session info:
R version 4.1.1 (2021-08-10)
Platform: aarch64-apple-darwin20 (64-bit)
Running under: macOS Monterey 12.1
Matrix products: default
LAPACK: /Library/Frameworks/R.framework/Versions/4.1-arm64/Resources/lib/libRlapack.dylib
locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] compiler_4.1.1 tools_4.1.1 RcppArmadillo_0.10.7.5.0
[4] Rcpp_1.0.7
Background
Currently (2023-02-20), CRAN builds R 4.2 binaries for Apple silicon using Apple clang from Command Line Tools for Xcode 13.1 and using an experimental fork of GNU Fortran 12.
If you obtain R from CRAN (i.e., here), then you need to replicate CRAN's compiler setup on your system before building R packages that contain C/C++/Fortran code from their sources (and before using Rcpp, etc.). This requirement ensures that your package builds are compatible with R itself.
A further complication is the fact that Apple clang doesn't support OpenMP, so you need to do even more work to compile programs that make use of multithreading. You could circumvent the issue by building R itself and all R packages from sources with LLVM clang, which does support OpenMP, but that approach is onerous and "for experts only".
There is another approach that has been tested by a few people, including Simon Urbanek, the maintainer of R for macOS. It is experimental and also "for experts only", but it works on my machine and is much simpler than learning to build R yourself.
Instructions for obtaining a working toolchain
Warning: These come with no warranty and could break at any time. Some level of familiarity with C/C++/Fortran program compilation, Makefile syntax, and Unix shells is assumed. Everyone is encouraged to consult official documentation, which is more likely to be maintained than answers on SO. As usual, sudo at your own risk.
I will try to address compilers and OpenMP support at the same time. I am going to assume that you are starting from nothing. Feel free to skip steps you've already taken, though you might find a fresh start helpful.
I've tested these instructions on a machine running Big Sur, and at least one person has tested them on a machine running Monterey. I would be glad to hear from others.
Download an R 4.2 binary from CRAN here and install. Be sure to select the binary built for Apple silicon.
Run
$ sudo xcode-select --install
in Terminal to install the latest release version of Apple's Command Line Tools for Xcode, which includes Apple clang. You can obtain earlier versions from your browser here. However, the version that you install should not be older than the one that CRAN used to build your R binary.
Download the gfortran binary recommended here and install by unpacking to root:
$ curl -LO https://mac.r-project.org/tools/gfortran-12.0.1-20220312-is-darwin20-arm64.tar.xz
$ sudo tar xvf gfortran-12.0.1-20220312-is-darwin20-arm64.tar.xz -C /
$ sudo ln -sfn $(xcrun --show-sdk-path) /opt/R/arm64/gfortran/SDK
The last command updates a symlink inside of the gfortran installation so that it points to the SDK inside of your Command Line Tools installation.
Download an OpenMP runtime suitable for your Apple clang version here and install by unpacking to root. You can query your Apple clang version with clang --version. For example, I have version 1300.0.29.3, so I did:
$ curl -LO https://mac.r-project.org/openmp/openmp-12.0.1-darwin20-Release.tar.gz
$ sudo tar xvf openmp-12.0.1-darwin20-Release.tar.gz -C /
After unpacking, you should find these files on your system:
/usr/local/lib/libomp.dylib
/usr/local/include/ompt.h
/usr/local/include/omp.h
/usr/local/include/omp-tools.h
Add the following lines to $(HOME)/.R/Makevars, creating the file if necessary.
CPPFLAGS += -I/usr/local/include -Xclang -fopenmp
LDFLAGS += -L/usr/local/lib -lomp
Run R and test that you can compile a program with OpenMP support. For example:
if (!requireNamespace("RcppArmadillo", quietly = TRUE))
install.packages("RcppArmadillo")
Rcpp::sourceCpp(code = '
#include <RcppArmadillo.h>
#ifdef _OPENMP
# include <omp.h>
#endif
// [[Rcpp::depends(RcppArmadillo)]]
// [[Rcpp::export]]
void omp_test()
{
#ifdef _OPENMP
Rprintf("OpenMP threads available: %d\\n", omp_get_max_threads());
#else
Rprintf("OpenMP not supported\\n");
#endif
}
')
omp_test()
OpenMP threads available: 8
If the C++ code fails to compile, or if it compiles without error but you get linker warnings or you find that OpenMP is not supported, then one of us has probably made a mistake. Please report any issues.
References
Everything is a bit scattered:
R Installation and Administration manual [link]
R for macOS Developers page [link]
I resolved this issue by adding a path to the homebrew installation of gfortran to my ~/.R/Makevars following these instructions: https://pat-s.me/transitioning-from-x86-to-arm64-on-macos-experiences-of-an-r-user/#gfortran
I just avoided the issue until MacOS had things working more smoothly. so I either Windows Developer Virtual Machine (VM) or run my code development in another environment. I'm not too impressed with the updated and "faster" chipset, but that it doesn't work with much. Slow to implement and work-a-rounds often are a must.
Tested the following process for making multithread data.table work in a M2 MacBook Pro (macOS Monterey)
Steps are mostly the same with this answer by the user inferator.
Download and install R from CRAN
Download and install RStudio with developer tools
Run the following commands in terminal to install OpenMP
curl -O https://mac.r-project.org/openmp/openmp-12.0.1-darwin20-Release.tar.gz
sudo tar fvxz openmp-12.0.1-darwin20-Release.tar.gz -C /
Add compiler flags to connect clan w/ OpenMP. In terminal, write the following:
cd ~
mkdir .R
nano .R/Makevars
Inside the opened Makevars file paste the following lines. Once finished, hit command+O and then Enter to save. Do a command+X to close the editor.
CPPFLAGS += -Xclang -fopenmp
LDFLAGS += -lomp
Download and run the installer for gfortran by downloading gfortran-ARM-12.1-Monterey.dmg from the respective GitHub repo
This concludes the steps regarding enabling OpenMP and (hopefully) Rcpp in R under a M2 chip system.
Now, for testing that everything works with data.table I did the following
Open RStudio and run
install.packages("data.table", type = "source")
If everything is done correctly, the package should compile without any errors and return the following when running getDTthreads(verbose = TRUE):
OpenMP version (_OPENMP) 201811
omp_get_num_procs() 8
R_DATATABLE_NUM_PROCS_PERCENT unset (default 50)
R_DATATABLE_NUM_THREADS unset
R_DATATABLE_THROTTLE unset (default 1024)
omp_get_thread_limit() 2147483647
omp_get_max_threads() 8
OMP_THREAD_LIMIT unset
OMP_NUM_THREADS unset
RestoreAfterFork true
data.table is using 4 threads with throttle==1024. See ?setDTthreads.
[1] 4
I'm trying to use packages that require Rcpp in R on my M1 Mac, which I was never able to get up and running after purchasing this computer. I updated it to Monterey in the hope that this would fix some installation issues but it hasn't. I tried running the Rcpp check from this page but I get the following error:
> Rcpp::sourceCpp("~/github/helloworld.cpp")
ld: warning: directory not found for option '-L/opt/R/arm64/gfortran/lib/gcc/aarch64-apple-darwin20.2.0/11.0.0'
ld: warning: directory not found for option '-L/opt/R/arm64/gfortran/lib'
ld: library not found for -lgfortran
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [sourceCpp_4.so] Error 1
clang++ -arch arm64 -std=gnu++14 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I../inst/include -I"/Library/Frameworks/R.framework/Versions/4.1-arm64/Resources/library/Rcpp/include" -I"/Library/Frameworks/R.framework/Versions/4.1-arm64/Resources/library/RcppArmadillo/include" -I"/Users/afredston/github" -I/opt/R/arm64/include -fPIC -falign-functions=64 -Wall -g -O2 -c helloworld.cpp -o helloworld.o
clang++ -arch arm64 -std=gnu++14 -dynamiclib -Wl,-headerpad_max_install_names -undefined dynamic_lookup -single_module -multiply_defined suppress -L/Library/Frameworks/R.framework/Resources/lib -L/opt/R/arm64/lib -o sourceCpp_4.so helloworld.o -L/Library/Frameworks/R.framework/Resources/lib -lRlapack -L/Library/Frameworks/R.framework/Resources/lib -lRblas -L/opt/R/arm64/gfortran/lib/gcc/aarch64-apple-darwin20.2.0/11.0.0 -L/opt/R/arm64/gfortran/lib -lgfortran -lemutls_w -lm -F/Library/Frameworks/R.framework/.. -framework R -Wl,-framework -Wl,CoreFoundation
Error in Rcpp::sourceCpp("~/github/helloworld.cpp") :
Error 1 occurred building shared library.
I get that it can't "find" gfortran. I installed this release of gfortran for Monterey. When I type which gfortran into Terminal, it returns /opt/homebrew/bin/gfortran. (Maybe this version of gfortran requires Xcode tools that are too new—it says something about 13.2 and when I run clang --version it says 13.0—but I don't see another release of gfortran for Monterey?)
I also appended /opt/homebrew/bin: to PATH in R so it looks like this now:
> Sys.getenv("PATH")
[1] "/opt/homebrew/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/Library/TeX/texbin:/Applications/RStudio.app/Contents/MacOS/postback"
Other things I checked:
Xcode command line tools is installed (which clang returns /usr/bin/clang).
Files ~/.R/Makevars and ~/.Renviron don't exist.
Here's my session info:
R version 4.1.1 (2021-08-10)
Platform: aarch64-apple-darwin20 (64-bit)
Running under: macOS Monterey 12.1
Matrix products: default
LAPACK: /Library/Frameworks/R.framework/Versions/4.1-arm64/Resources/lib/libRlapack.dylib
locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] compiler_4.1.1 tools_4.1.1 RcppArmadillo_0.10.7.5.0
[4] Rcpp_1.0.7
Background
Currently (2023-02-20), CRAN builds R 4.2 binaries for Apple silicon using Apple Clang from Command Line Tools for Xcode 13.1 and using an experimental fork of GNU Fortran 12.
If you obtain R from CRAN (i.e., here), then you need to replicate CRAN's compiler setup on your system before building R packages that contain C/C++/Fortran code from their sources (and before using Rcpp, etc.). This requirement ensures that your package builds are compatible with R itself.
A further complication is the fact that Apple Clang doesn't support OpenMP, so you need to do even more work to compile programs that make use of multithreading. You could circumvent the issue by building R itself, all R packages, and all external libraries from sources with LLVM Clang, which does support OpenMP, but that approach is onerous and "for experts only".
There is another approach that has been tested by a few people, including Simon Urbanek, the maintainer of R for macOS. It is experimental and also "for experts only", but it works on my machine and is much simpler than learning to build R and other libraries yourself.
Instructions for obtaining a working toolchain
Warning: These come with no warranty and could break at any time. Some level of familiarity with C/C++/Fortran program compilation, Makefile syntax, and Unix shells is assumed. Everyone is encouraged to consult official documentation, which is more likely to be maintained than answers on SO. As usual, sudo at your own risk.
I will try to address compilers and OpenMP support at the same time. I am going to assume that you are starting from nothing. Feel free to skip steps you've already taken, though you might find a fresh start helpful.
I've tested these instructions on a machine running Big Sur, but they should also work on Monterey and Ventura.
Download an R 4.2 binary from CRAN here and install. Be sure to select the binary built for Apple silicon.
Run
$ sudo xcode-select --install
in Terminal to install the latest release version of Apple's Command Line Tools for Xcode, which includes Apple Clang. You can obtain earlier versions from your browser here. However, the version that you install should not be older than the one that CRAN used to build your R binary.
Download the GNU Fortran binary provided here and install by unpacking to root:
$ curl -LO https://mac.r-project.org/tools/gfortran-12.0.1-20220312-is-darwin20-arm64.tar.xz
$ sudo tar xvf gfortran-12.0.1-20220312-is-darwin20-arm64.tar.xz -C /
$ sudo ln -sfn $(xcrun --show-sdk-path) /opt/R/arm64/gfortran/SDK
The last command updates a symlink inside of the installation so that it points to the SDK inside of your Command Line Tools installation.
Download an OpenMP runtime suitable for your Apple Clang version here and install by unpacking to root. You can query your Apple Clang version with clang --version. For example, I have version 1300.0.29.3, so I did:
$ curl -LO https://mac.r-project.org/openmp/openmp-12.0.1-darwin20-Release.tar.gz
$ sudo tar xvf openmp-12.0.1-darwin20-Release.tar.gz -C /
After unpacking, you should find these files on your system:
/usr/local/lib/libomp.dylib
/usr/local/include/ompt.h
/usr/local/include/omp.h
/usr/local/include/omp-tools.h
Add the following lines to $(HOME)/.R/Makevars, creating the file if necessary.
CPPFLAGS += -I/usr/local/include -Xclang -fopenmp
LDFLAGS += -L/usr/local/lib -lomp
Test that you are able to use R to compile a C or C++ program with OpenMP support while linking relevant libraries from the GNU Fortran installation (indicated by the -l flags in the output of R CMD CONFIG FLIBS).
The most transparent approach is to use R CMD SHLIB directly. In a temporary directory, create an empty source file omp_test.c and add the following lines:
#ifdef _OPENMP
# include <omp.h>
#endif
#include <Rinternals.h>
SEXP omp_test(void)
{
#ifdef _OPENMP
Rprintf("OpenMP threads available: %d\n", omp_get_max_threads());
#else
Rprintf("OpenMP not supported\n");
#endif
return R_NilValue;
}
Compile it:
$ R CMD SHLIB omp_test.c $(R CMD CONFIG FLIBS)
Then call the compiled C function from R:
$ R -e 'dyn.load("omp_test.so"); invisible(.Call("omp_test"))'
OpenMP threads available: 8
If the compiler or linker throws an error, or if you find that OpenMP is still not supported, then one of us has made a mistake. Please report any issues.
Note that you can implement the same test using Rcpp, if you don't mind installing it:
library(Rcpp)
registerPlugin("flibs", Rcpp.plugin.maker(libs = "$(FLIBS)"))
sourceCpp(code = '
#ifdef _OPENMP
# include <omp.h>
#endif
#include <Rcpp.h>
// [[Rcpp::plugins(flibs)]]
// [[Rcpp::export]]
void omp_test()
{
#ifdef _OPENMP
Rprintf("OpenMP threads available: %d\\n", omp_get_max_threads());
#else
Rprintf("OpenMP not supported\\n");
#endif
return;
}
')
omp_test()
OpenMP threads available: 8
References
Everything is a bit scattered:
R Installation and Administration manual [link]
Writing R Extensions manual [link]
R for macOS Developers web page [link]
I resolved this issue by adding a path to the homebrew installation of gfortran to my ~/.R/Makevars following these instructions: https://pat-s.me/transitioning-from-x86-to-arm64-on-macos-experiences-of-an-r-user/#gfortran
I just avoided the issue until MacOS had things working more smoothly. so I either Windows Developer Virtual Machine (VM) or run my code development in another environment. I'm not too impressed with the updated and "faster" chipset, but that it doesn't work with much. Slow to implement and work-a-rounds often are a must.
Tested the following process for making multithread data.table work in a M2 MacBook Pro (macOS Monterey)
Steps are mostly the same with this answer by the user inferator.
Download and install R from CRAN
Download and install RStudio with developer tools
Run the following commands in terminal to install OpenMP
curl -O https://mac.r-project.org/openmp/openmp-12.0.1-darwin20-Release.tar.gz
sudo tar fvxz openmp-12.0.1-darwin20-Release.tar.gz -C /
Add compiler flags to connect clan w/ OpenMP. In terminal, write the following:
cd ~
mkdir .R
nano .R/Makevars
Inside the opened Makevars file paste the following lines. Once finished, hit command+O and then Enter to save. Do a command+X to close the editor.
CPPFLAGS += -Xclang -fopenmp
LDFLAGS += -lomp
Download and run the installer for gfortran by downloading gfortran-ARM-12.1-Monterey.dmg from the respective GitHub repo
This concludes the steps regarding enabling OpenMP and (hopefully) Rcpp in R under a M2 chip system.
Now, for testing that everything works with data.table I did the following
Open RStudio and run
install.packages("data.table", type = "source")
If everything is done correctly, the package should compile without any errors and return the following when running getDTthreads(verbose = TRUE):
OpenMP version (_OPENMP) 201811
omp_get_num_procs() 8
R_DATATABLE_NUM_PROCS_PERCENT unset (default 50)
R_DATATABLE_NUM_THREADS unset
R_DATATABLE_THROTTLE unset (default 1024)
omp_get_thread_limit() 2147483647
omp_get_max_threads() 8
OMP_THREAD_LIMIT unset
OMP_NUM_THREADS unset
RestoreAfterFork true
data.table is using 4 threads with throttle==1024. See ?setDTthreads.
[1] 4
I'm porting my Qt app to Linux for x86 architecture, and since the last official release for that platform is 5.5, I'm trying to do my own build of Qt 5.11.3. I want to use fontconfig to enable use of system fonts. My build platform is Centos 7.5, and I'm using a GCC toolchain which builds x86 binaries with -m32 switch.
The problem is, I can't get it to see the fontconfig library. I've installed it with the package fontconfig-devel-2.13.0-4.3.el7.i686
When running configure with the option -fontconfig, I get the following error message:
ERROR: Feature 'fontconfig' was enabled, but the pre-condition '!config.win32 && features.system-freetype && libs.fontconfig' failed.
My understanding from this is that I have to use -system-freetype and can't use -qt-freetype, but when I try that (also with -feature-freetype), I get this message:
ERROR: Feature 'system-freetype' was enabled, but the pre-condition 'features.freetype && libs.freetype' failed.
The relevant messages in config.log are:
looking for library freetype
Trying source 0 (type pkgConfig) of library freetype ...
pkg-config use disabled globally.
=> source produced no result.
Trying source 1 (type freetype) of library freetype ...
+ cd /home/myuser/qt-build/config.tests/freetype && /home/myuser/qt-build/qtbase/bin/qmake "CONFIG -= qt debug_and_release app_bundle lib_bundle" "CONFIG += shared warn_off console single_arch" -early "CONFIG += cross_compile" 'LIBS += -lfreetype' /home/myuser/qt-build/config.tests/freetype
+ cd /home/myuser/qt-build/config.tests/freetype && MAKEFLAGS= /usr/bin/gmake
> g++ -c -m32 -pipe -O2 -std=gnu++11 -w -fPIC -I. -I/home/myuser/qt-everywhere-src-5.11.3/qtbase/mkspecs/linux-g++-32 -o main.o main.cpp
> main.cpp:2:22: fatal error: ft2build.h: No such file or directory
> #include <ft2build.h>
> ^
> compilation terminated.
> gmake: *** [main.o] Error 1
=> source failed verification.
test config.qtbase_gui.libraries.freetype FAILED
Now, I do also get this message:
WARNING: Cross compiling without sysroot. Disabling pkg-config
which I understand is the source of the "source 0" failure. I have however tried to point configure manually point it to the freetype include directory, by passing FREETYPE_INCDIR=/usr/include/freetype2 to configure; however, as can be seen in the log file, the value does not seem to be used when detecting freetype.
Am I missing a trick here, or are the configure scripts broken? And if it's the latter, is there a way to work around this?
EDIT: For completeness, the environment for running configure:
CFLAGS=-m32
CXXFLAGS=-m32 --std=c++1x
Configure flags:
-opensource
-xplatform linux-g++-32
-nomake tests -nomake examples -nomake tools
-prefix /home/myuser/qt_install/
-qpa xcb
-no-use-gold-linker
-icu ICU_PREFIX=/home/myuser/icu_install ICU_LIBS="-licui18n -licuuc -licudata"
-no-opengl
-fontconfig -feature-freetype -system-freetype FREETYPE_INCDIR=/usr/include/freetype2
Try using the Freetype library that is included inside Qt's sources: when running configure use the flag "-qt-freetype"
I've found it's possible to work around this by setting CPATH (and LIBRARY_PATH to point at a specific build of Freetype which it turned out I needed as well). It looks like the fact that FREETYPE_* variables are ignored when detecting the presence of Freetype is indeed a bug in the config scripts.
I am trying to build my Qt project with C++11 standard. I added this flag in the build steps, additional argument option, in the Qt Creator :
-std=c++11
But I got this error while building :
Unknown option -std=c++11
g++ version info : g++ (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3
Any ideas ?
Use the qmake project file, add this line: QMAKE_CXXFLAGS += -std=c++11
LE: also 4.6.3 might not support C++11 (as far as i know 4.7 and higher support -std=c++11) so the option for the 0x features implemented might be: QMAKE_CXXFLAGS += -std=c++0x
If you are using Qt5, add CONFIG += c++11 to your .pro file, that works on all systems.
Let's say I have a library lib1.so created like that:
gcc 1.cpp -o lib1.so -shared
And I have another library lib2.so created in this way:
gcc 2.cpp -o lib2.so -shared -L. -l1
But linking against lib2.so
gcc main.cpp -o main -L. -l2
gives a warning:
warning: lib1.so, needed by lib2.so, not found (try using -rpath or -rpath-link)
But AFAIK the use of rpath is discouraged because then the library can not be moved to another location.
How do I link "main" against "lib2.so" without specifying "lib1.so" and rpath?
The RPATH header in the binary takes precedence so even if the library has no RPATH header, it will still be found IF you have copied it to the directory mentioned in -rpath