I am facing the following problem, I am trying to convert an std::string object into an std::basic_string<char8_t> one, using the codecvt library. The code is the following:
#include <string>
#include <codecvt>
#include <locale>
int main()
{
std::string str = "Test string";
std::wstring_convert <std::codecvt_utf8_utf16 <char8_t>, char8_t> converter_8_t;
converter_8_t.from_bytes( str );
}
The problem is that when I try to compile it with g++ -std=c++20 (g++ 11.2.0) I got the following error:
/usr/bin/ld: /tmp/cck8g9Wa.o: in function `std::__cxx11::wstring_convert<std::codecvt_utf8_utf16<char8_t, 1114111ul, (std::codecvt_mode)0>, char8_t, std::allocator<char8_t>, std::allocator<char> >::wstring_convert()':
other.cpp:(.text._ZNSt7__cxx1115wstring_convertISt18codecvt_utf8_utf16IDuLm1114111ELSt12codecvt_mode0EEDuSaIDuESaIcEEC2Ev[_ZNSt7__cxx1115wstring_convertISt18codecvt_utf8_utf16IDuLm1114111ELSt12codecvt_mode0EEDuSaIDuESaIcEEC5Ev]+0x2c): undefined reference to `std::codecvt_utf8_utf16<char8_t, 1114111ul, (std::codecvt_mode)0>::codecvt_utf8_utf16(unsigned long)'
collect2: error: ld returned 1 exit status
Do you know what could be the problem? Am I trying to convert the std::string object in the wrong way? Thanks.
C++ keywords: char8_t (since C++20)
As far as I understand char8_t is of char type as is your std::string. A simple cast should work.
Related
I have created a project with intention of using hunspell functions in it. I am working in Ubuntu. I installed and compiled hunspell library and linked it with g++ -o wc.exe -lhunspell-1.6 wordcheck.cxx and everything seemed ok. But when I tried to compile and launch my project I got some errors.
#include <iostream>
#include "hunspell/hunspell.hxx"
using namespace std;
int main(int argc,char** argv)
{
FILE* lst=fopen("wordlist.txt","r");
if(!lst)
{
cerr<<"Can not open file\n";
return 1;
}
Hunspell* hs=new Hunspell(argv[1],argv[2]);
delete hs;
return 0;
}
and the errors were:
/home/alex2/Документы/bO/wordcheck.cxx:14: undefined reference to Hunspell::Hunspell(char const*, char const*, char const*)'
/home/alex2/Документы/bO/wordcheck.cxx:15: undefined reference toHunspell::~Hunspell()'
collect2: error: ld returned 1 exit status
atus
I have no idea what is wrong. I tried using
Hunspell* hs=new Hunspell();
and got that there is a candidate for it that requires three parameters:
/usr/local/include/hunspell/hunspell.hxx:115:3: note: candidate: Hunspell::Hunspell(const char*, const char*, const char*)
Hunspell(const char* affpath, const char* dpath, const char* key = NULL);
The only difference is char const* and const char* but I always thought it is the same thing. The entire project is similar to the example file hunspell provides and I have no idea what am I doing wrong and why my thing is not working.
I have install leveldb in my home directory ~/local like this.
[~/temp/leveldb-1.15.0] $ make
[~/temp/leveldb-1.15.0] $ cp -av libleveldb.* $HOME/local/lib/
[~/temp/leveldb-1.15.0] $ cp -av include/leveldb $HOME/local/include/
My c++ program like this：
#include <assert.h>
#include <iostream>
#include "leveldb/db.h"
using namespace std;
int main(int argc,char * argv[])
{
leveldb::DB* db;
leveldb::Options options;
options.create_if_missing = true;
std::string dbpath = "tdb";
leveldb::Status status = leveldb::DB::Open(options, dbpath, &db);
assert(status.ok());
std::string key1 = "grz";
std::string key2 = "grz-rt#63.com";
cout<<"Open db OK"<<std::endl;
std::string value;
leveldb::Status s ;
s = db->Put(leveldb::WriteOptions(), key1, key2);/*key1和key2作为一对key-value对插入*/
s = db->Get(leveldb::ReadOptions(), key1, &value);/*根据key返回对应的value值*/
cout<<value<<std::endl;
delete db;/*删除数据库*/
return 0;
}
I compile this C++ program like this：
g++ -o Main Main.cpp ~/local/lib/libleveldb.a -lpthread -I ~/local/include/
But I get the error like this：
/public/home/kli/local/lib/libleveldb.a(table_builder.o): In function `leveldb::TableBuilder::WriteBlock(leveldb::BlockBuilder*, leveldb::BlockHandle*)':
table_builder.cc:(.text+0x678): undefined reference to `snappy::MaxCompressedLength(unsigned long)'
table_builder.cc:(.text+0x6b2): undefined reference to `snappy::RawCompress(char const*, unsigned long, char*, unsigned long*)'
/public/home/kli/local/lib/libleveldb.a(format.o): In function `leveldb::ReadBlock(leveldb::RandomAccessFile*, leveldb::ReadOptions const&, leveldb::BlockHandle const&, leveldb::BlockContents*)':
format.cc:(.text+0x5de): undefined reference to `snappy::GetUncompressedLength(char const*, unsigned long, unsigned long*)'
format.cc:(.text+0x64e): undefined reference to `snappy::RawUncompress(char const*, unsigned long, char*)'
collect2: ld returned 1 exit status
I don't know what's wrong.
I am new to Linux. Thank you very much!
libleveldb.a misses Snappy when being linked which would be probably in libsnappy.a in the same directory.
Looks like the Makefile is incomplete.
With the current install, you need to edit the Makefile to link against snappy and to include -L/usr/local/lib instead of -L/usr/local/include.
(Will post pull request later)
Here's my code. I'm just testing Boost::process so I'll be able to use it if/when I need to. I don't know why I'm getting the linking error that I am getting. I'm a rather novice C++ programmer. I know the concepts, but I make frequent errors in practice and am bad at debugging. I appreciate any help I can get with this.
#include<iostream>
#include<boost/process.hpp>
#include<boost/iostreams/device/file_descriptor.hpp>
namespace bp = ::boost::process;
namespace bpi = ::boost::process::initializers;
namespace bio = ::boost::iostreams;
int main(int argc, char *argv[])
{
bp::pipe p = bp::create_pipe();
bio::file_descriptor_sink sink(p.sink, bio::close_handle);
bp::execute(
bpi::run_exe("/usr/bin/ls"),
bpi::bind_stdout(sink)
);
return(0);
}
And here is my error…
/tmp/cc7cmrV8.o: In function `main':
test.cpp:(.text+0x2b): undefined reference to `boost::iostreams::file_descriptor_sink::file_descriptor_sink(int, boost::iostreams::file_descriptor_flags)'
/tmp/cc7cmrV8.o: In function `boost::process::posix::initializers::bind_stdout::bind_stdout(boost::iostreams::file_descriptor_sink const&)':
test.cpp:(.text._ZN5boost7process5posix12initializers11bind_stdoutC2ERKNS_9iostreams20file_descriptor_sinkE[_ZN5boost7process5posix12initializers11bind_stdoutC5ERKNS_9iostreams20file_descriptor_sinkE]+0x2b): undefined reference to `boost::iostreams::file_descriptor_sink::file_descriptor_sink(boost::iostreams::file_descriptor_sink const&)'
/tmp/cc7cmrV8.o: In function `void boost::process::posix::initializers::bind_stdout::on_exec_setup<boost::process::posix::executor>(boost::process::posix::executor&) const':
test.cpp:(.text._ZNK5boost7process5posix12initializers11bind_stdout13on_exec_setupINS1_8executorEEEvRT_[_ZNK5boost7process5posix12initializers11bind_stdout13on_exec_setupINS1_8executorEEEvRT_]+0x18): undefined reference to `boost::iostreams::file_descriptor::handle() const'
collect2: error: ld returned 1 exit status
Platform: Linux 64-bit
Boost: 1.55 (installed via pacman)
Boost::process: 0.5
Compile command: g++ -Wall test.cpp -o spegh.elf -lboost_system
A simple search threw me at -This-.
Seeing you posted your compile command, I'm guessing you are simply missing -lboost_iostreams in your linker settings.
I've been working on porting one of my games to Linux and can't seem to figure out the reasons for the errors I'm received. The game was originally written in Visual Studio 2010 and I have extracted all of the needed content (headers, cpp, textures) and am trying to compile.
Compilation of files using g++ -c -o exampleFile.o exampleFile.cpp works fine without any errors. However upon linking I am greeted with hundreds of errors regarding std functions, an example:
Bmp.o: In function `Image::Bmp::Bmp()':
Bmp.cpp:(.text+0x58): undefined reference to `std::allocator<char>::allocator()'
Bmp.cpp:(.text+0x74): undefined reference to `std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, std::allocator<char> const&)'
Bmp.cpp:(.text+0x80): undefined reference to `std::allocator<char>::~allocator()'
Bmp.cpp:(.text+0x91): undefined reference to `std::allocator<char>::~allocator()'
Full output can be found on PasteBin
The Bmp.cpp file is a library function written by someone else, it can be found here The code eluded to above is:
#include <fstream>
#include <iostream>
#include <cstring>
#include "Bmp.h"
using std::ifstream;
using std::ofstream;
using std::ios;
using std::cout;
using std::endl;
using namespace Image;
///////////////////////////////////////////////////////////////////////////////
// default constructor
///////////////////////////////////////////////////////////////////////////////
Bmp::Bmp() : width(0), height(0), bitCount(0), dataSize(0), data(0), dataRGB(0),
errorMessage("No error.")
{
}
Bmp::Bmp(const Bmp &rhs)
{
// copy member variables from right-hand-side object
width = rhs.getWidth();
height = rhs.getHeight();
bitCount = rhs.getBitCount();
dataSize = rhs.getDataSize();
errorMessage = rhs.getError();
if(rhs.getData()) // allocate memory only if the pointer is not NULL
{
data = new unsigned char[dataSize];
memcpy(data, rhs.getData(), dataSize); // deep copy
}
else
data = 0; // array is not allocated yet, set to 0
if(rhs.getDataRGB()) // allocate memory only if the pointer is not NULL
{
dataRGB = new unsigned char[dataSize];
memcpy(dataRGB, rhs.getDataRGB(), dataSize); // deep copy
}
else
dataRGB = 0; // array is not allocated yet, set to 0
}
Not really sure what the issue is, but it strikes me that the linker can't reach the std functions? Thanks in advance for any help.
Edit Linking command: gcc -o LDTux Bmp.o character.o chickenList.o chicken.o farmList.o farm.o fieldList.o field.o generall_utils.o landscape.o object.o SZ_NumberList.o SZ_Sprite.o worm.o wormList.o wormSpawn.o wormSpawnList.o GameWorld.o HelloOpenGL.o -lGL -lglut -lm
As pointed out earlier by Dietmar Kühl in the comments,
you should change the linker command from gcc to g++.
As pointed out by Dietmar Kühl in the comments, I was using gcc to link, rather than g++.
Upon amending the linking command, I received ...undefined reference to 'gluLookAt' which was fixed by adding -lGLU.
I am just trying to make a vector, but it gives me a huge error and I am following a working example from my other project. The code:
#include <stdio.h>
#include <stdlib.h>
#include <vector>
using namespace std;
struct organism {
bool One;
bool Two;
};
std::vector<organism> organisms;
int main() {
printf("Content-type: text/html\n\n");
printf("TEST");
printf(getenv("QUERY_STRING"));
return 0;
}
The error:
> "make"
C:/MinGW/bin/gcc.exe -o build/e2.exe source/main.cpp
C:\Users\Stephen\AppData\Local\Temp\ccc0a0w2.o:main.cpp:(.text$_ZN9__gnu_cxx13new_allocatorI8organismE10deallocateEPS1_j[__gnu_cxx::new_allocator<organism>::deallocate(organism*, unsigned int)]+0xd): undefined reference to `operator delete(void*)'
C:\Users\Stephen\AppData\Local\Temp\ccc0a0w2.o:main.cpp:(.eh_frame$_ZNSt12_Vector_baseI8organismSaIS0_EED2Ev+0x13): undefined reference to `__gxx_personality_v0'
C:\Users\Stephen\AppData\Local\Temp\ccc0a0w2.o:main.cpp:(.eh_frame$_ZNSt6vectorI8organismSaIS0_EED1Ev+0x13): undefined reference to `__gxx_personality_v0'
collect2: ld returned 1 exit status
"make": *** [build] Error 1
> Process Exit Code: 2
> Time Taken: 00:01
I can compile it if I comment out std::vector<organism> organisms; but I have no clue what's wrong with that line. It's exactly the same in my other project, which compiles fine.
You need to compile with g++.exe instead of gcc.exe so that it will know it needs to link with the C++ library.