I'm trying to get emscripten to work on OS X 10.8, see this post for some related issues there. Apparently the clang++ version shipped with Xcode is too old, so I got a recent clang 3.7.0 using MacPorts. I even told CMake to use that compiler (passing -DCMAKE_CXX_COMPILER=clang++-mp-3.7 on the command line), but it still fails:
[ 33%] Building CXX object CMakeFiles/optimizer.dir/parser.cpp.o
/opt/local/bin/clang++-mp-3.7 -std=c++11 -fno-exceptions -fno-rtti -O3 -DNDEBUG
-o CMakeFiles/optimizer.dir/parser.cpp.o
-c …/emsdk/emscripten/master/tools/optimizer/parser.cpp
In file included from …/emsdk/emscripten/master/tools/optimizer/parser.cpp:2:
In file included from …/emsdk/emscripten/master/tools/optimizer/parser.h:12:
…/emsdk/emscripten/master/tools/optimizer/istring.h:3:10: fatal error:
'unordered_set' file not found
#include <unordered_set>
^
1 error generated.
I can reproduce that issue by launching the compiler from the command line. In parallel build mode, sometimes it's instead complaining about <cstdint> for optimizer.cpp instead. Both these headers exist in /opt/local/libexec/llvm-3.7/include/c++/v1/.
What's the canonical way to use the macports-installed version of clang++ including its headers? Do I have to use -I and work out the full path, or is there something shorter?
Can I safely do so without also switching the runtime library to the one shipped with MacPorts' clang? If not, can I somehow encode the full path of the runtime library into the created binary, either for that single library or using the -rpath argument to ld or some equivalent alternative?
Update: I get unresolved symbols when I try to link stuff after specifying the include directory manually, and I don't know how to solve that. The libcxx package from MacPorts is empty except for a readme file.
I've solved the original problem by adding CXXFLAGS=--stdlib=libc++ to the environment. Then even the system version of clang will do everything I need. That flag works magic for MacPorts' version of clang as well: specifying that I get a successful build, and I can even verify (using the -E compiler switch) that it's using the headers I mentioned before. I'm still not certain whether there is anything to ensure that the headers match the system's version of libc++, though.
Related
I was trying to include the GMP library, which was simply the code below(I did nothing else):
#include <gmpxx.h>
However, when I tried to compile the code, the following error from g++ compiler occured:
myCode.cpp:3:10: fatal error: gmpxx.h: No such file or directory
#include <gmpxx.h>
^~~~~~~~~~~~~~~~~~~~~~
I have tried everything I searched online, putting the GMP lib here and there, adding INFINITE includepaths in c_cpp_properties.json, still, it keeps showing the message, although, I can find the file through "Go to Definition" option.
Is there any known solution to this?
It's not enough to configure VS Code includes, you need to pass those options to the compiler as well.
You don't mention your platform at all, so I'm going to use an example from my personal machine, a Macbook Pro with the fmt library.
When compiling with the fmt library, I have to provide three more options to the compiler.
-I/usr/local/include // Tells the compiler where to look for extra includes
-L/usr/local/lib // Tells the compiler where to look for extra libraries
-lfmt // fmt-specific command to use fmt library
So the full command ends up looking like this:
g++ -Wall -std=c++17 -I/user/local/include -L/usr/local/lib -lfmt main.cpp
I need all three options because fmt is installed in a non-standard location that the compiler doesn't check by default. According to the documentation, you can get away with just -lgmp and -lgmpxx if you installed the library in a standard location (happens by default with *nix and a package manager, I imagine).
If you use build tasks in VS Code, this can be set up and automated for you.
[Mac OS 10.13.2, Xcode9.2]
Clang has a flag -stdlib which, according to both clang++ -cc1 --help (same as clang -cc1 --help) and the LLVM documentation page, allows specification of the C++ standard library to use.
1) How does this flag impact on compilation? I.e. does it change the order of library include paths etc.
2) How does this flag impact linking? I.e. is it just a short-cut/alternative for supplying -lc++?
I am really interested in understanding the details of this flag because I can't find any documentation describing it's precise behaviour and it is causing havoc with our build system since the Xcode9 upgrade. Inclusion of -stdlib=libc++ in our Makefile causes the compilation to fail due to headers problems, yet, when -stdlib=libc++ is omitted, our projects compile fine (presumably because libc++ is the Mac OS default Standard C++ library). The project link against libc++ due to other linker flags -lc++ and -lsupc++.
Some background info about our use-case
We are using Clang to cross-compile to a -march=i686 -target i686-linux-elf target. Prior to the Xcode9 update, our build system was working fine. Since the upgrade we're getting compiler errors, such as:
/usr/local/our-target/sysroot/usr/local/include/c++/v1/stdlib.h:111:82: error: use of undeclared identifier 'labs'; did you mean 'abs'?
inline _LIBCPP_INLINE_VISIBILITY long abs( long __x) _NOEXCEPT {return labs(__x);}
I've now been able to fix this problem by changing the header include paths. Namely I have removed a path reference to the folder that is parent to both the libc++ AND gcc4.8.5 includes.
# -I${STAGING.nao}/usr/local/include/c++ \
-I${STAGING.nao}/usr/local/include/c++/v1
I am still very interested in understanding the details of what the flag does.
I'm trying to use cuda in ns3, but when I tried to run CXX="nvcc" ./waf configure, it shows the following message on the screen:
Checking for 'g++' (C++ compiler) : not found
Checking for 'clang++' (C++ compiler) : not found
Checking for 'icpc' (C++ compiler) : not found
could not configure a C++ compiler!
(complete log in /home/kelu/workspace/ns-3.24/build/config.log)
I checked the config.log, it says the following:
Checking for 'g++' (C++ compiler)
find program='nvcc' paths=['/usr/local/sbin', '/usr/local/bin', '/usr/sbin', '/usr/bin', '/sbin', '/bin', '/usr/local/cuda/bin'] var='CXX' -> ['nvcc']
from /home/kelu/workspace/ns-3.24: Could not determine the compiler type
not found
----------------------------------------
Checking for 'clang++' (C++ compiler)
find program='nvcc' paths=['/usr/local/sbin', '/usr/local/bin', '/usr/sbin', '/usr/bin', '/sbin', '/bin', '/usr/local/cuda/bin'] var='CXX' -> ['nvcc']
from /home/kelu/workspace/ns-3.24: Not clang/clang++
not found
----------------------------------------
Checking for 'icpc' (C++ compiler)
find program='nvcc' paths=['/usr/local/sbin', '/usr/local/bin', '/usr/sbin', '/usr/bin', '/sbin', '/bin', '/usr/local/cuda/bin'] var='CXX' -> ['nvcc']
from /home/kelu/workspace/ns-3.24: Not icc/icpc
not found
from /home/kelu/workspace/ns-3.24: could not configure a C++ compiler!
nvcc is located in /usr/local/cuda/bin, which is in path. But it seems to me that the building script of ns3 does not resolve nvcc as a compiler.
Could anybody please tell me the right way to make nvcc the CXX compiler in ns3?
Thanks.
Your problem probably was that Waf actually checks the compiler's built-in #defines to check whether a compiler invoked as "gcc" actually is gcc or not. As a concrete example, it will error out if it detects that the compiler is Intel's icc (because it #defined __INTEL_COMPILER) but was invoked with a "gcc" command line!
The code that does the identification is at https://waf.io/apidocs/_modules/waflib/Tools/c_config.html#get_cc_version .
So, if you don't have a compiler which tries hard to look like one of the supported ones, looks like you are supposed to write your own Waf tool.
However, you can try to hack your way through. For example, let's say that your compiler is compatible enough with gcc but still it doesn't get past Waf's absurdly stringent test. A fix is to run "waf configure" using the real gcc, and then edit the file where Waf stores the detection results, so at the build step Waf will actually run your compiler instead of gcc. You can do this by editing build/c4che/_cache.py: change the CC definition to your compiler's full path.
I haven't found a way to use nvcc in ns-3, but I did find a work around for this problem. I'm happy to share my solution here to help others:
Make your cuda code a static library:
ar rcs libcudacode.a a.o b.o c.o (you need to make the *.o files first using g++, nvcc, or anything else you want)
put libcudacode.a in /your/lib/folder/ and put your cuda code in /your/src/folder
Add lib folder and src folder into waf:
CXXFLAGS_EXTRA="-I/your/src/folder -I/your/cuda/dir/include" LINKFLAGS_EXTRA="-L/your/lib/folder -L/your/cuda/dir/lib64 -lcudacode -lcudart" ./waf configure.
./waf
Your code should be compiled now. You can access any public functions in your cuda code by #including "corresponding_header.h"
A little bit explanation:
CXXFLAGS_EXTRA and LINKFLAGS_EXTRA add compilation flags in ns-3's compiling system. You need to add both your cuda code and NVidia's cuda library to use the functions.
If you used any other libraries, also put them in CXXFLAGS_EXTRA and LINKFLAGS_EXTRA
Check the cuda directory name in your system. It's probably not lib64 in your machine.
Earlier, I posed a related question.
I have the following program extracted from a large project in my Mac OS
#include <iostream>
int main(){
std::cout<<"hello"<<std::endl;
return 0;
}
Compiling it with Clang fails with the following error:
$ clang test.cpp
test.cpp:1:10: fatal error: 'iostream' file not found
#include <iostream>
^
1 error generated.
For information,
A) I have already installed xcode command line tools, using xcodeselect --install. But it seems iostream does not locate in the default search path of clang.
B) Using g++ instead of clang compiles the program. But in my problem, I am not allowed to use other compiler than clang, or to change the source program.
C) I can see workaround techniques, e.g, by tweaking the search path in .bashrc or with some symbolic link, etc. But I feel reluctant to use them, because it seems that I have an installation problem with my Clang and tweaking the path only helps to avoid one of these path issues.
clang and clang++ do different things. If you want to compile C++ code, you need to use clang++
Alternatively you can invoke c++ compiler directly by providing language name explicitely:
clang -x=c++
I'm having the same problem described in this post except I'm using Intel version 12.1.3. (g++'s header <functional> is protected with #ifdef __GXX_EXPERIMENTAL_CXX0X__ which is not defined when icpc is used.)
Instead of using boost::functional, I wanted to install gcc4.7 and use it's std libraries.
In Ubuntu 11.10 I have gcc4.6.1 but I also installed gcc4.7 from the gcc-snapshot package.
Intel has the options -gcc-name, -gxx-name, and -cxxlib.
So originally I compiled with:
-std=c++0x -gcc-name=/usr/lib/gcc-snapshot/bin/gcc -gxx-name=/usr/lib/gcc-snapshot/bin/g++ -cxxlib=/usr/lib/gcc-snapshot/
but I get the error:
icpc: error #10282: file
'/usr/lib/gcc-snapshot/bin/usr/lib/gcc-snapshot/bin/g++' not found,
generated based on '-cxxlib=/usr/lib/gcc-snapshot/'
So then I compiled with:
-std=c++0x -gcc-name=./gcc -gxx-name=./g++ -cxxlib=/usr/lib/gcc-snapshot/.
But I still get the warnings and errors:
Warning #2928: the __GXX_EXPERIMENTAL_CXX0X__ macro is disabled when using GNU version 4.6 with the c++0x option
error: namespace "std" has no member "function"
The warning clearly says it's still using version 4.6. Does anybody know how to get Intel to use the correct libraries?
I've found that if you compile with gcc (or g++) with flags -v -Q you get a list of flags and defines. It might help you see what gcc does so maybe you can use the same -D/-U in icpc. also g++ -E will preprocess without compiling: you can get useful path information from that.