C++ type traits compilation problem with gcc

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 5
  • gcc 4.1.2

Issue

Compilation of C++ code fails with the following:

/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/ios_base.h: In copy constructor ‘std::basic_ios<char, std::char_traits<char> >::basic_ios(const std::basic_ios<char, std::char_traits<char> >&)’:
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/ios_base.h:779: error: ‘std::ios_base::ios_base(const std::ios_base&)’ is private
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/iosfwd:55: error: within this context
ostream.cpp: In copy constructor ‘MyOutputStream::MyOutputStream(const MyOutputStream&)’:
ostream.cpp:29: note: synthesized method ‘std::basic_ios<char, std::char_traits<char> >::basic_ios(const std::basic_ios<char, std::char_traits<char> >&)’ first required here 
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/streambuf: In copy constructor ‘MyStreamBuf::MyStreamBuf(const MyStreamBuf&)’:
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/streambuf:781: error: ‘std::basic_streambuf<_CharT, _Traits>::basic_streambuf(const std::basic_streambuf<_CharT, _Traits>&) [with _CharT = char, _Traits = std::char_traits<char>]’ is private
ostream.cpp:8: error: within this context
ostream.cpp: In copy constructor ‘MyOutputStream::MyOutputStream(const MyOutputStream&)’:
ostream.cpp:29: note: synthesized method ‘MyStreamBuf::MyStreamBuf(const MyStreamBuf&)’ first required here 
ostream.cpp: In copy constructor ‘MsgParam::MsgParam(const MsgParam&)’:
ostream.cpp:54: note: synthesized method ‘MyOutputStream::MyOutputStream(const MyOutputStream&)’ first required here 
ostream.cpp: In function ‘int main(int, char**)’:
ostream.cpp:76: note: synthesized method ‘MsgParam::MsgParam(const MsgParam&)’ first required here

Resolution

Use gcc 4.4 or later

Root Cause

  • This specific test case is relying on a C++ feature (support for type traits) that was only implemented in a later version of gcc.

  • Specifically this was implemented between gcc 4.2 and 4.3 with the following commit: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26099

Diagnostic Steps

A small example of C++ code showing the issue:

#include <fstream>
#include <iostream>
#include <stdlib.h>
#include <string>

static const char * const FOO = "foo";

class MyStreamBuf : public std::streambuf {
    public:
        MyStreamBuf(char* pBuffer, size_t size) : m_pBuffer(pBuffer),
                              m_size(size) {
            setp(m_pBuffer, m_pBuffer + m_size);
        }
        MyStreamBuf(size_t size = 64) : m_pBuffer(new char[size]),
                            m_size(size) {
            setp(m_pBuffer, m_pBuffer + m_size);
        }
        const char* str() {
            return m_pBuffer;
        }
    private:
        char* m_pBuffer;
        size_t m_size;
};

class MyOutputStream : private std::ostream {
    public:
        MyOutputStream(char *buf, size_t size) : std::ios(0), 
                               std::ostream(__null),
                               msb(buf, size) {
            std::ostream::rdbuf(&msb);
        }

        MyOutputStream(size_t size = 64) : std::ios(0),
                             std::ostream(__null),
                             msb(size) {
            std::ostream::rdbuf(&msb);
        }
        const char* str() {
            return msb.str();
        }

    private:
        MyStreamBuf msb;
}; 

class MsgParam
{
    public:
        template <class T> MsgParam(T i_param): m_params(128) {
            m_params << i_param;
        }

        MsgParam& operator+(const MsgParam& i_msgParam);
        operator const char*() { return getParams(); }
        const char* getParams() {
            m_paramStr = m_params.str();
            return m_paramStr.c_str();
        }
    private:
        MyOutputStream m_params;
        std::string m_paramStr;
};


int main (int argc, char *argv[]) {
    int ret = 0;
    std::cout << MsgParam(FOO) + MsgParam(FOO);
    std::cout << "ret :" << ret << "end\n";
    return 0;
}
  • Component
  • gcc

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