[Bug 1829415] [NEW] printing bitset to_string().c_str() in template produces junk

[P Touchman]

Public bug reported:


I am trying to print a bitset with printf using a template, but I keep getting junk on the output.

I can print a bitset with
printf("%s",std::bitset<32>(valuetoprint).to_string().to_cstr());

but I thought it would be nice to do that with a template so I could
just go:

printf("%s",mybitset<32>(valuetoprint));


template <const int mysize,class mytype> const char * mybitset(mytype myobj){ return std::bitset<mysize>(myobj).to_string().c_str(); }

template <const int mysize> const char * mybitset2(int myobj){ return
std::bitset<mysize>(myobj).to_string().c_str(); }

template <const int mysize> const char * mybitset3(int myobj){ return
std::bitset<mysize>(myobj).template
to_string<char,std::char_traits<char>,std::allocator<char>>().c_str(); }

template <const int mysize> const char * mybitset4(int myobj){ return
std::bitset<mysize>(myobj).template
to_string<char,std::char_traits<char>,std::allocator<wchar_t>>().c_str();
}

template <const int mysize> std::string mybitset5(int myobj){ return
std::bitset<mysize>(myobj).template
to_string<char,std::char_traits<char>,std::allocator<char>>(); }


printf("testing bitset32 %s  "     ,std::bitset<32>(0x255+0xf000).to_string().c_str());
printf("testing bitset16 %s  "     ,std::bitset<16>(0x255+0xf000).to_string().c_str());
printf("testing mybitset32 %s  "   ,mybitset<32,int>(0x255+0xf000));
printf("testing mybitset8 %s  "    ,mybitset<8,int>(0x255+0xf000));
printf("testing mybitset2 16 %s  " ,mybitset2<16>(0x255+0xf000));
printf("testing mybitset2 15 %s "  ,mybitset2<15>(0x255+0xf000));
printf("testing mybitset2 8 %s "   ,mybitset2<8>(0x255+0xf000));
printf("testing mybitset2 16 %s "  ,mybitset2<16>(0x255+0xf000));
printf("testing mybitset3 15 %s "  ,mybitset3<15>(0x255+0xf000));
printf("testing mybitset3 8 %s "   ,mybitset3<8>(0x255+0xf000));
printf("testing mybitset3 16 %s \n",mybitset3<16>(0x255+0xf000));
printf("testing mybitset4 16 %s \n",mybitset4<16>(0x255+0xf000));

std::cout << "mybitset5" << mybitset5<16>(0x255+0xf000) << "\n";


and the output I get is:

testing bitset32 00000000000000001111001001010101  testing bitset16 1111001001010101  testing mybitset32 `w�3V  testing mybitset8 01010101  testing mybitset2 16 `w�3V  testing mybitset2 15 111001001010101 testing mybitset2 8 01010101 testing mybitset2 16 `w�3V  testing mybitset3 15 111001001010101 testing mybitset3 8 01010101 testing mybitset3 16 `w�3V  
testing mybitset4 16 `w�3V  
mybitset51111001001010101

So my template works fine up until I try to make it print a bitset of
size 16.  It works fine for a bitset of size 15 but not for 16.

I also tried this compiling with clang and it did the same thing,
outputting garbage, working fine for a template with bitset size 15 and
garbage for 16.

** Affects: gcc-7 (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1829415

Title:
  printing bitset to_string().c_str()  in template produces  junk

Status in gcc-7 package in Ubuntu:
  New

Bug description:
  
  I am trying to print a bitset with printf using a template, but I keep getting junk on the output.

  I can print a bitset with
  printf("%s",std::bitset<32>(valuetoprint).to_string().to_cstr());

  but I thought it would be nice to do that with a template so I could
  just go:

  printf("%s",mybitset<32>(valuetoprint));

  
  template <const int mysize,class mytype> const char * mybitset(mytype myobj){ return std::bitset<mysize>(myobj).to_string().c_str(); }

  template <const int mysize> const char * mybitset2(int myobj){ return
  std::bitset<mysize>(myobj).to_string().c_str(); }

  template <const int mysize> const char * mybitset3(int myobj){ return
  std::bitset<mysize>(myobj).template
  to_string<char,std::char_traits<char>,std::allocator<char>>().c_str();
  }

  template <const int mysize> const char * mybitset4(int myobj){ return
  std::bitset<mysize>(myobj).template
  to_string<char,std::char_traits<char>,std::allocator<wchar_t>>().c_str();
  }

  template <const int mysize> std::string mybitset5(int myobj){ return
  std::bitset<mysize>(myobj).template
  to_string<char,std::char_traits<char>,std::allocator<char>>(); }


  printf("testing bitset32 %s  "     ,std::bitset<32>(0x255+0xf000).to_string().c_str());
  printf("testing bitset16 %s  "     ,std::bitset<16>(0x255+0xf000).to_string().c_str());
  printf("testing mybitset32 %s  "   ,mybitset<32,int>(0x255+0xf000));
  printf("testing mybitset8 %s  "    ,mybitset<8,int>(0x255+0xf000));
  printf("testing mybitset2 16 %s  " ,mybitset2<16>(0x255+0xf000));
  printf("testing mybitset2 15 %s "  ,mybitset2<15>(0x255+0xf000));
  printf("testing mybitset2 8 %s "   ,mybitset2<8>(0x255+0xf000));
  printf("testing mybitset2 16 %s "  ,mybitset2<16>(0x255+0xf000));
  printf("testing mybitset3 15 %s "  ,mybitset3<15>(0x255+0xf000));
  printf("testing mybitset3 8 %s "   ,mybitset3<8>(0x255+0xf000));
  printf("testing mybitset3 16 %s \n",mybitset3<16>(0x255+0xf000));
  printf("testing mybitset4 16 %s \n",mybitset4<16>(0x255+0xf000));

  std::cout << "mybitset5" << mybitset5<16>(0x255+0xf000) << "\n";

  
  and the output I get is:

  testing bitset32 00000000000000001111001001010101  testing bitset16 1111001001010101  testing mybitset32 `w�3V  testing mybitset8 01010101  testing mybitset2 16 `w�3V  testing mybitset2 15 111001001010101 testing mybitset2 8 01010101 testing mybitset2 16 `w�3V  testing mybitset3 15 111001001010101 testing mybitset3 8 01010101 testing mybitset3 16 `w�3V  
  testing mybitset4 16 `w�3V  
  mybitset51111001001010101

  So my template works fine up until I try to make it print a bitset of
  size 16.  It works fine for a bitset of size 15 but not for 16.

  I also tried this compiling with clang and it did the same thing,
  outputting garbage, working fine for a template with bitset size 15
  and garbage for 16.

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