I need to know in a library, if a specific header file is included or not.
like
//a.cpp
#include <array>
#include "incl.hpp"
//incl.hpp
//check if array is included or not
I can do by checking _GLIBCXX_ARRAY and ARRAY macro for g++ and msvc. Can you please tell me how to do the equivalent in clang ?
Related
I'm trying to integrate CUDA to an existing aplication wich uses boost::spirit.
Isolating the problem, I've found out that the following code does not copile with nvcc:
main.cu:
#include <boost/spirit/include/qi.hpp>
int main(){
exit(0);
}
Compiling with nvcc -o cudaTest main.cu I get a lot of errors that can be seen here.
But if I change the filename to main.cpp, and compile again using nvcc, it works. What is happening here and how can I fix it?
nvcc sometimes has trouble compiling complex template code such as is found in Boost, even if the code is only used in __host__ functions.
When a file's extension is .cpp, nvcc performs no parsing itself and instead forwards the code to the host compiler, which is why you observe different behavior depending on the file extension.
If possible, try to quarantine code which depends on Boost into .cpp files which needn't be parsed by nvcc.
I'd also make sure to try the nvcc which ships with the recent CUDA 4.1. nvcc's template support improves with each release.
I installed some encryption software called libntru.
The header files are installed in /usr/include/libntru and the file I would like to include from this directory is ntru.h. The compiled library is installed to /usr/lib/libntru.so.
In my makefile, I use gcc's -L and -l flags to link to the library as such -L/usr/lib -lntru, however in my project, I get a compiler error at the line #include <ntru.h>.
How can I link to this library? Thanks in advance for any help.
Check on the instructions with the software; there's at least a chance you're supposed to write one of:
#include <libntru/ntru.h>
#include "libntru/ntru.h"
If that's the case, you won't need to specify anything on the command line to find the headers (no -I option). If you're supposed to write just:
#include <ntru.h>
#include "ntru.h"
Then you need to add -I/usr/include/libntru to the command line.
Note that you probably don't need -L/usr/lib on the command line; the compiler will normally look there anyway, but you will need the -lntru option to specify the library itself, of course.
I am writing a program that will use the array container of the C++ Standard Library to hold some objects. However, whenever I try to include the following line of code in my program:
#include <array>
I receive the following error at compile time:
75-143-76-177:soft jeffersonhudson$ g++ mms.cpp -o mms
mms.cpp:5:17: error: array: No such file or directory
75-143-76-177:soft jeffersonhudson$
Commenting out the #include lets me compile just fine. Surely I am overlooking something simple? I have installed the "Command Line Tools" in Xcode, am I still missing something?
EDIT:
I have found the location of array on my computer
/usr/clang-ide/lib/c++/v1
knowing that, what should I do?
<array> is provided in C++11, you need to provide the -std=c++11 flag to enable it, and provide the -stdlib=libc++ flag for the corresponding library. But the g++ provided by Xcode is so old which doesn't have much support for C++11. Could you switch to clang?
clang++ -std=c++11 -stdlib=libc++ mms.cpp -o mms
from the looks of it, you are not using LLVM's libc++, but GCC's libstdc++.
to use std::array in the latter context, use:
#include <tr1/array>
if you want to use libc++ and C++11, then alter your compiler flags as KennyTM suggested (+1).
I'm trying to compile an application that utilizes cstdint. Since Apple deprecated the gcc, I wanted to try compiling it with clang, but i get the error:
fatal error: 'cstdint' file not found
I know that the gcc 4.6.2 version has the option for -std=c++0x, to include the library, but since the os x version is 4.2 that's not much of an option here. Any suggestions on how I can move forward? I have tried to install 4.6.2, but ran into a variety of issues when compiling some of the needed libraries before building gcc.
Presumably, you have the source code to this application, so you can modify the headers to include the correct cstdint header, as Clang 3.0 (which Lion's tools come with) does have the header.
Quick Solution
The header is under the tr1 directory, so you will want to do either of these includes:
#include <tr1/cstdint>
Or
#include <stdint.h> // which will use the C99 header
Longer, boring explanation
After doing some additional reading since I remember you can do this without the tr1 directory:
By default, you are going to be including C++ headers from /usr/include/c++/4.2.1, which are the GNU GCC headers. /usr/include/c++/4.2.1/tr1 includes the TR1 header files, like cstdint.
The alternative method is to compile using the Clang++ frontend and passing the -stdlib=libc++ flag, which will use the headers from /usr/include/c++/v1, which are Clang's C++ header implementations. It has cstdint.
Example:
// file called example.cxx
#include <tr1/cstdint>
int main() {
// whatever...
}
Compile this with:
g++ example.cxx
or
clang++ example.cxx
And it will do what you want.
If you don't want to use the tr1 version (which is roughly the same, if not exactly):
// file called example.cxx
#include <cstdint>
int main() {
// stuff
}
This is compiled like this:
clang++ -stdlib=libc++ example.cxx
Though if you use -stdlib=libc++, it means you're linking to Clang's C++ library libc++, rather than GCC's libstdc++.
I have a mixture of c and c++ files compiling under g++. As explained in:
What is the difference between g++ and gcc?
The c files are being compiled as c++ with the g++ command line. Not huge problem but migrating over to gcc will allow th c files to compile as c files and the c++ file to compile as c++.
What -I includes or -L libraries do I need to add to the gcc command line, that the g++ command line is including by default?
You shouldn't need to add any includes or libraries beyond what you already have.
Whatch out for C functions being called from C++ code - you need to tell the C++ compiler those are C functions so the program is linked correctly and works.
The standard practice is to add the following directives to all your C headers being included in C++ files:
#ifdef __cplusplus
extern "C" {
#endif
... C header contents go here ...
#ifdef __cplusplus
}
#endif
More info here: http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html
You shouldn't need to add any. If it's using C++ it should automatically bring in C++ libraries.
If not, you'll want -lstdc++ (and if you're still getting undefined references, -lc for the libc). Don't forget -lm if you use math functions.
GCC can determine which language a file is in based on the file extension. However, GCC does not automatically link in run time support for any language other than C. In practice that means you can compile C++ programs using gcc instead of g++ but you'll need to add the -lstdc++ directive:
#include <iostream>
int main()
{
std::cout << "Hello world\n";
}
g++ hello.cc
gcc hello.cc -lstdc++
More accurately, you will need to specify -lstdc++ if you you use the standard library, exceptions, operator new, or RTTI. For instance, try compiling the following without -lstdc++:
int main()
{
try {
throw 1;
}
catch (int i)
{
return i;
}
}
Please note that STL containers (including std::strings) use operator new by default. Strictly speaking you should be able to use the algorithms (std::min, std::find_first_of, etc.) binders and a few other things in the standard library without -lstdc++ but for the most part you might as well include it (the linker will ignore any libraries that you don't actually link to).
Why not compile the c objects with gcc and the c++ with g++ and then when you link, link using the g++?