I was trying an openmp code with clang compiler as specified in
http://clang-omp.github.io/
I downloaded the code via git and did make and make install. It successfully installed the clang compiler with openmp support. But when I try to compile a sample code (specified in the above link), I get the following error :
/usr/bin/ld: cannot find -liomp5
I did not specify path to include and lib as mentioned in the site, but I intend to specify them while compiling on command line with -L and -I options.
$clang -I/usr/lib/gcc/i686-linux-gnu/4.6/include -fopenmp test.c -o test
However, I could not find path for iomp5 lib and hence I got the above error. Can someone please tell me how to resolve this?
At first you need to build openmp library libiomp5. You can take the latest source code here
http://llvm.org/svn/llvm-project/openmp/trunk/
Related
I am currently using clang11 on ubuntu to compile any c/c++ code and it works fine but when I tried to compile any code (including any standard library) to assembly code for any specific target like x86_64 (even I have x86_64) riscv with giving a flag that --target=x86_64 or --target=riscv32 I got errors for any standard library that I included in my code. A simple example:
// ex.cpp
#include<iostream>
int main(){
int a = 5;
int b = 3;
std::cout << a - b;
}
Without giving flag for a spesific target works fine:
clang++-11 -S ex.cpp -o ex.s
With --target=riscv32 flag:
clang++-11 --target=riscv32 -S ex.cpp -o ex.s
gives this error:
ex.cpp:1:9: fatal error: 'iostream' file not found
also without standard libraries gives no error even I give a spesific target.
I am searching for a solution for days but I couldn't find any proper solution for this problem, most of them says try to include gnu libraries and subfolders like -I/usr/include/x86_64-linux-gnu/c++/ but it doesn't work for me.
Please don't say use g++ compiler, for adding an optimization I need clang.
Actually I am trying to compile my codes for riscv target, linking with g++ and running with spike (doesn't differ --target=... or -target ...):
clang++-11 -target riscv32-unknown-elf -march=rv32gc -fno-addrsig -S ex.cpp -o ex.s
~/riscv/bin/riscv32-unknown-elf-g++ ex.s -o ex
~/riscv/riscv-isa-sim/build/spike --isa=RV32GC ~/riscv/riscv-pk/build/pk ex
And it works fine without include a standard library.
Now, I want to ask that
Can I solve this problem simply?
or
Can I use clang directly from riscv bin utils like ~/riscv/bin/riscv32-unknown-elf-clang++ (I saw something like this on the net but couldn't find) adding and building a submodule to my riscv directory?
Edit: As #NateEldredge said, for x86_64 target triple should --target=x86_64-linux-gnu but for riscv as a target triple riscv32-unknown-elf I still have the same errors. Is there a proper target flag for riscv any other than --target=riscv32-unknown-elf? Maybe I am missing that point.
I solved my problem by linking compilations with riscv-gnu-toolchain built and also answered a similar question here in detailed: Using Clang to compile for RISC-V
Simply we need cross-compilation.
Further information you can also look here: https://github.com/lowRISC/riscv-llvm#how-can-i-build-upstream-llvmclang-and-use-it-to-cross-compile-for-a-riscv32-target
I'm using mingw-w64 (gcc 7.3.0) and when I compile any C++ program using the following command:
g++ file.cpp -fsanitize=undefined
I get the following error:
...mingw32/bin/ld.exe: cannot find -lubsan
I'm able to successfully compile and run my programs if I remove the -fsanitize=undefined flag, though. After some research I found out that this means the library ubsan (Undefined Behavior Sanitizer) is missing, but I couldn't find anything about the library. How do I fix this?
This is well known issue with mingw see for instance this msys github issue. No proper solution known but there are several WAs.
Install WSL, ubuntu over WSL and you will have ubsan inside it
Build GCC under Windows from source enabling sanitizers build. They are present in GCC sources they are just not here in mingw.
Use -fsanitize=undefined -fsanitize-undefined-trap-on-error to just not use libubsan rich logging capabilities but get it trap on undefined instruction.
Hope one of this helps.
I have installed OpenBlas in TX1 and the time_dgemm example compiles fine with the gcc. However, I need to be able to link the rest of my code with OpenBlas using g++. When I try to compile the time_dgemm example with g++ it fails, giving the linking error "...undefined reference to 'dgemm_(......". The only change is using the g++ instead of gcc.
I have tried to compile the OpenBLAS library with g++ (make CC=g++), as other people suggested in the past, but the compilation fails when it tries to compile some part of BLAS.
Any ideas?
If some people have the same issue, I was able to compile with the following command:
g++ openBlasExample.cpp -I /usr/include/openblas -lopenblas
You can find your openblas include folder by using on Linux:
locate openblas
More info here:
https://gist.github.com/xianyi/6930656
I have a package that depends on Rcpp and uses two other libraries compiled from sub-directories in src/. The package builds fine on Mac OSX using a clang compiler. However, on an RStudio Ubuntu server, it fails to build. The build's first two steps (creating the static libraries in the sub directories to link in) work fine and I can see sensible build commands like the following taking place:
g++ -Wall -I../../inst/include/ --std=c++11 -lhts -L../htslib/ -lz -lm -c -o someLibFile.o someLibFile.cpp
However, in the very last step of the build process where it tries to build the Rcpp code and bind to the library, for some reason it appears to compleletey fail to put the compiler command in front (g++) and only outputs the second half of the command.
-o mypackage.so RcppExports.o temp.o -lhts -lpbbam -Lpbbam/ -L/htslib/ -Lpbbam/ -L/mnt/software/r/R/3.1.1/usr/lib/R/lib -lR
In contrast, on the Mac it builds just fine, appending clang++ and other flags in front of this final command:
clang++ -std=c++11 -dynamiclib -Wl,-headerpad_max_install_names -undefined dynamic_lookup -single_module -multiply_defined suppress -L/Library/Frameworks/R.framework/Resources/lib -L/usr/local/lib -o pbbamr.so LoadData.o RcppExports.o temp.o -lhts -lpbbam -Lpbbam/ -Lhtslib/ -Lpbbam/ -F/Library/Frameworks/R.framework/.. -framework R -Wl,-framework -Wl,CoreFoundation
How do I make it use the g++ compiler on Ubuntu at this step? I have a custom Makevars file, but it is there just to build the dependencies in the sub-directory, so I don't know why that would cause any problems (since it works on Mac OSX).
More Information
The compiler seems to be found if I delete my Makevars file. However, the Makevars file I am using is essentially a direct copy of the example given in the R extensions guide with one addition to enable C++11:
CXX_STD = CXX11
.PHONY: all mylibs
all: $(SHLIB)
$(SHLIB): mylibs
mylibs:
(cd subdir; make)
With the line CXX_STD removed, it does stick a compiler in front of the command.
Briefly:
What is your R installation? You should probably run the binaries provided by Michael via CRAN; they are based on my Debian upload; I run these too on a bunch of machines
The reason is that R 'remembers' its compile-time settings via $RHOME/etc/Makefconf. This should just be CXX=g+=.
When you install r-base-dev (from Ubuntu or the newer version from CRAN) you also get the build-essential package as well as all common dependencies. With that things just work.
If however you are doing something special or local, well then you have to deal with your local changes. The basic Ubuntu setup is used by thousands of people and daily jobs--including eg Travis builds for countless GitHub repos.
This is caused by using an outdated/unusual R installation which has poor support for C++11. The best way to resolve his is to upgrade to a more recent version of R, or use a standard R install (sudo apt-get install r-base-dev). A poor work around is described below.
Problems Cause and Bad Work Around
When writing R extension that use C++11, one often sets CXX_STD = CXX11 in the Makevars file or list SystemRequirements: C++11 in the DESCRIPTION file. These will trigger R to use the compiler set by the following flags in the Makeconf file (located at file.path(R.home(), "etc/Makeconf")).
CXX1X
CXX1XFLAGS
CXX1XPICFLAGS
CXX1XSTD
Note that some of these may be set in this file, but not all of them might be there indicating a problem. In the event there is a problem with these settings or they are not set, R appears to use the empty string "" as the compiler/linker for the C++ code, leading to the problem shown above where no compiler argument is given.
If upgrading is not an option and you need to deploy on a known machine, one work around is to manually setup for C++11 by making a more idiosyncratic Makevars file. For example, you could:
Remove the CXX_STD=CXX11 line from the Makevars file.
Remove SystemRequirements: C++11 from the DESCRIPTION file.
Add --std=c++11 and any other requirements needed to PKG_CPPFLAGS, PKG_CFLAGS, PKG_CXXFLAGS or whatever variable is being used to compile your code, to manually set the needed flags (assuming the machine's compiler actually does support C++11).
The above solution is not particularly robust, but can be used as a work around in case the machine cannot be upgraded.
Thanks to #DirkEddelbuettel for not only writing Rcpp but being willing to support it on StackOverflow and help with issues like this.
I wanted to use latest g++ compiler(4.9.1) on suse linux, but suse only supports an older g++ version. So, I took a latest source code from one of the gnu mirror sites and compiled it myself. Everything went fine. But when I tried to compile my test code using the built g++, the compilation fails with error,
"/root/home/include/c++/4.9.1/x86_64-unknown-linux-gnu/bits/os_defines.h:39:22: fatal error: features.h: No such file or directory".
I can find a "features.h" in "/root/home/include/c++/4.9.1/parallel", but I feel that it should be there in "/root/home/include/c++/4.9.1/" itself.
I copied "/root/home/include/c++/4.9.1/parallel/features.h" to "/root/home/include/c++/4.9.1/" just to see what happens. Now it complains with error "whcar.h" not found.
Have I missed something.
Here are the steps I followed to build g++.
1. /root/home/gcc_build/objdir# ../gcc-4.9.1/configure --prefix=/root/home/ --disable-multilib
2. /root/home/gcc_build/objdir# make -j16
3. /root/home/gcc_build/objdir# make install
4. /root/home/gcc_build/test# /root/home/bin/g++ --sysroot /root/home -m64 test.cpp
I resolved the issue by removing sysroot option and pointing c++ include and library path to my home directory. One thing I noticed was that the g++ source does not come with libc and c header files, and libc has to be installed seperately. But with sysroot option, g++ was trying to look all the header files in my home directory.
Below is the command I used to successfully compile the code.
/root/home/bin/g++ -I /root/home/include/c++/4.9.1 -L /root/home/lib64 -Wl,--rpath=/root/home/lib64 --std=c++0x -m64 test.cpp
Take a look at the GCC Directory Options. It is important to use the correct "specifier" as well (-isystem, -L, -B, -I etc)