This program doesn't actually do anything, but it builds with 182 warnings, all of which seem to be issues in boost code. Should I do anything about this, maybe use a different library, or should I just use boost::asio and ignore all the warnings?
// main.cpp
#include <boost/asio.hpp>
#include <boost/asio/ssl.hpp>
int main() {
exit(0) ;
}
This is common for many boost (and third-party) libraries. I would have them treated as system headers. For example, with gcc pass the -isystem command line option or move the boost headers to directory which is considered a system header directory.
Boost also has a warnings guidelines page which might be helpful. See Suppressing Warnings in GCC.
Related
I am now trying to build a c++ library in linux with cmake. If I do not enable -std=c++0x option, I always get compilation errors error: 'div_t' was not declared in this scope for the following codes:
int xPos;
div_t divResult;
divResult = div(xPos,8);
Then if I enable -std-c++0x options with cmake: set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x", then everything is fine. However, in my library I did not use any c++0x features, so I am reluctant to set std=c++0x option. So I search the head file that defines div_t and find it is defined in stdlib.h within the following MACRO:
__BEGIN_NAMESPACE_STD
typedef struct
{
int quot;
int rem;
} div_t;
....
....
__END_NAMESPACE_STD
It seems to me that if I can enable these macros I can build the library without enabling c++0x feature. So my question is what I can do in this situation.
By the way, I can build the library very well without enabling c++0x feature if only g++4.4 is installed in the linux machine. When I also install g++4.6 and make g++4.6 the default g++, then the compilation error began to occur. Even I changed the default g++ to g++4.4, the compilation error still exists if I do not enable c++0x feature.
The macros expand to namespace std { and } respectively if the code is pulled in through a C++ standard library header. This leads me to believe that you're not #including stdlib.h directly (which is good!).
Earlier versions of libstdc++ pulled symbols from C legacy headers into the global namespace even if the C++ versions of these headers (e.g. <cstdlib> instead of <stdlib.h>) were used; newer ones place them only in namespace std.
The cleanest way to fix this is to
#include <cstdlib>
in all translation units where the problem occurs and to use std::div instead of div. If you're lazy, you can also
#include <stdlib.h>
in all translation units that use div, but mixing C and C++ is always icky. Not terribad in this particular case, though.
I want to debug SGI STL in g++ (version 4.1.2)
I downloaded source code in http://www.sgi.com/tech/stl/download.html and put them in a directory,such as /stl
and then g++ -I/stl m.cpp
but it causes a lot of complie errs,why?
m.cpp
#include "list" //I want to include **/STL** not **/usr/include/c++/...**
using namespace std
int main()
{return 0;}
Thanks
I just want to debug SGI STL in g++,what should I do?Is this feasible???
Gcc looks here (subject to your exact setup)
GCC looks in several different places for headers. On a normal Unix system, if you do not instruct it otherwise, it will look for headers requested with #include in:
/usr/local/include
libdir/gcc/target/version/include
/usr/target/include
/usr/include
But you can change that easily with g++ -nostdinc -I/stl m.cpp.
The compiler errors are likely cause by the different built in code, but we can't tell without seeing them.
I have the following very simple application that compiles and runs fine:
EDIT: changed the example to be simpilar to end confusion of the real issue
int main() {
return 0;
}
As soon as I add #include <string> (and not even reference std::string), it fails to compile and I get the following error:
/usr/include/c++/4.1.2/bits/allocator.h:82 error: expected template-name before '<' token
Along with about 456 other, similar errors.
Any ideas? Thanks!
UPDATE:
Line 82 of /usr/include/c++/4.1.2/bits/allocator.h references the template __glibcxx_base_allocator at the location of the error. That template is defined in bits/c++allocator.h. When I search the system for that file, I get 3 hits, but none of them are in /usr/include/c++/4.1.2/bits/ as one would expect.
I have version 3.1.6, 4.1.1, and 4.3.2, but not 4.1.2 as the rest of the includes I am using. I am not sure which one is being used (if any, however, I don't get any error for an unknown file), but it seems the problem may stem from this.
The problem appears to be the installed development packages are not correct or incomplete (not to be confused with corrupt). Forcing g++ to use different include versions corrects that:
g++ -nostdic++ hello.cc -o hello -I/usr/include/c++/3.4.6
All the alternative directories (4.1.1, 4.1.2 and 4.3.2) are incomplete causing inappropriate files to be included causing the unusually errors. For example:
/usr/include/c++/4.1.2/bits/allocator.h requires __glibcxx_base_allocator located in bits/c++allocator.h which is being included from either /usr/include/c++/4.1.1 or /usr/include/c++/4.3.2 and appear to be incompatible. Forcing the compiler to use the only complete set of includes rectifies this.
Almost certainly g++ is detecting .cc as a C source file, not C++ and passes it through to gcc instead of compiling as C++. You can easily test by renaming your file to hello.C. There's also a language parameter to g++ you can use.
EDIT: This seems to work fine in g++ 4.2 with a .cc extension so that might not be it. Do you have any other headers included you aren't showing us? They could be interfering with <string>.
EDIT2: Alternatively your headers might not be set up right. Does this work:
#include <string>
int main()
{
return 0;
}
Errors like this have been heard of to occur when the C++ standard library headers are corrupted/not fully installed – maybe there is even a message referring to a missing include among your 456 other errors.
In any case, make sure that libstdc++-devel, resp. the package containing the C++ standard library header files of your distribution, is properly installed.
Check your include path. The paths can be specified as environment variables or specified on the command line. You could be using an include file from a different compiler or different version of the same compiler.
Also, try using <cstdio> rather than <stdio.h>.
Another suggestion: change <> to "".
This could be error caused at preprocess stage. Just preprocess your cpp file by passing flag -E to gcc and Look at the place the compiler complains.
This is more of an answer than a question, because I've figured it out, at least as far as cleanly compiling the library. The main issue for me was to get shared_ptr working.
Ingredients:
Boost v. 1.45.0
The version of STLport at http://www.anddev.org/viewtopic.php?p=29939.
Version r4b of the NDK.
Directions:
In your Android.mk file add:
LOCAL_CFLAGS += -DBOOST_EXCEPTION_DISABLE -D_STLP_NO_EXCEPTIONS -DOS_ANDROID -D_STLP_USE_SIMPLE_NODE_ALLOC
Remove the call to __stl_throw_length_error at line 613 of stlport/stl/_string.h. You can use _STLP_NO_EXCEPTIONS if you like.
Edit boost/boost/smart_ptr/shared_ptr.hpp after line 261 to get rid of the call to boost::throw_exception in the shared_ptr constructor. I used #ifndef BOOST_EXCEPTION_DISABLE around the entire body of the method. (But see the answer below.)
Next you need to supply some missing pieces. Create a header file with the following:
#ifdef OS_ANDROID
#include <exception>
namespace std
{
struct bad_alloc : public exception { bad_alloc operator()(){}};
}
#endif
and a source file with a stripped-down exception class to support bad_alloc:
#ifdef OS_ANDROID
#include <exception>
namespace std
{
exception::exception() {}
exception::~exception() {}
const char* exception::what() const {}
}
#endif
Include the header wherever you're including boost/shared_ptr.hpp. Compile the source and add it to your library.
It turned out that this approach does not entirely work when compiling a debuggable library. The release library is compiled with -O2 which optimizes out some infelicities, but the debug library is done with -O0 which reveals some additional problems. Furthermore, I wasn't too happy about having to edit the boost files. So with some additional study, I've come up with the following solution.
First, don't edit any of the boost files. Instead add the following to the header within the std namespace:
struct bad_cast : public exception {bad_cast operator()(){}};
Next add the following to the source file:
namespace boost
{
void throw_exception(std::exception const&) {}
}
This now compiles and links into the application even with android:debuggable="true" in AndroidManifest.xml. It doesn't run in the emulator, but then it wasn't doing that before I included this library either.
Notably, NDK r5 comes with STLport, and the GNU STL, and so the hacks here are no longer going to be necessary now that there is a) STL support b) exception support in the NDK C++ compiler.
Another workaround for shared_ptr in particular is to use boost::intrusive_ptr instead. This is not always possible, but worked for my situation.
The current version of Android NDK (r9) now supports exceptions.
The capabilities of the various runtimes vary. See this table:
C++ C++ Standard
Exceptions RTTI Library
system no no no
gabi++ yes yes no
stlport yes yes yes
gnustl yes yes yes
stlport can get used in non-GPL binarys. It's still flagged as experimantal, but you can use it with clang and gcc.
See http://developer.android.com/tools/sdk/ndk/
I have this program which uses Boost::Asio for sockets. I pretty much altered some code from the Boost examples. The program compiles and runs just like it should on Windows in VS. However, when I compile the program on Linux and run it, I get a Segmentation fault.
I posted the code here
The command I use to compile it is this:
c++ -I/appl/htopopt/Linux_x86_64/NTL-5.4.2/include
-I/appl/htopopt/Linux_x86_64/boost_1_43_0/include
mpqs.cpp mpqs_polynomial.cpp mpqs_host.cpp -o mpqs_host
-L/appl/htopopt/Linux_x86_64/NTL-5.4.2/lib -lntl
-L/appl/htopopt/Linux_x86_64/gmp-4.2.1/lib -lgmp -lm
-L/appl/htopopt/Linux_x86_64/boost_1_43_0/lib -lboost_system
-lboost_thread -static -lpthread
By commenting out code, I have found out that I get the Segmentation fault due to the following line:
boost::asio::io_service io_service;
Can anyone provide any assistance, as to what may be the problem (and the solution)?
Thanks!
Edit: I tried changing the program to a minimal example, using no other libraries or headers, just boost/asio.hpp:
#define DEBUG 0
#include <boost/asio.hpp>
int main(int argc, char* argv[]) {
boost::asio::io_service io_service;
return 0;
}
I also removed other library inclusions and linking on compilation, however this minimal example still gives me a segmentation fault.
From the GCC online documentation of the -static option:
On systems that support dynamic linking, this prevents linking with the shared libraries.
Boost can support static-only linkage but only if it was configured that way when the OS Package maintainer built it. Are you absolutely certain you should be using this flag? If not, try recompiling without the flag and see if that doesn't take care of the problem.