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  1. #include <ostream>
  2. #include <iostream>
  3. #include <locale>
  4.  
  5. using namespace std;
  6.  
  7. inline int geti() { 
  8.     static int i = ios_base::xalloc();
  9.     return i;
  10. }
  11.  
  12. // rename it to something better
  13. struct my_num_put : num_put<char> {
  14.     static const std::ios_base::fmtflags reqFlags
  15.     	= (std::ios_base::showbase | std::ios_base::hex);
  16.  
  17.     iter_type 
  18.     do_put(iter_type s, ios_base& f, char_type fill, long v) const {
  19.         if (v == 0 && ((f.flags() & reqFlags) == reqFlags)) {
  20.             *(s++) = '0';
  21.             *(s++) = 'x';
  22.         }
  23.         return num_put<char>::do_put(s, f, fill, v);
  24.     } 
  25.  
  26.     iter_type 
  27.     do_put(iter_type s, ios_base& f, char_type fill, unsigned long v) const { 
  28.           if (v == 0 && ((f.flags() & reqFlags) == reqFlags)) {
  29.             *(s++) = '0';
  30.             *(s++) = 'x';
  31.         }
  32.         return num_put<char>::do_put(s, f, fill, v);
  33.     } 
  34. }; 
  35.  
  36. int main() {
  37. 	// wrong
  38.     std::cout << std::showbase << std::hex << 0 << ' ' << 11 << std::endl;
  39.  
  40.     // fixed by workaround
  41.     std::cout.imbue(std::locale(std::locale(), new my_num_put));
  42.     std::cout << std::showbase << std::hex << 0 << ' ' << 11 << std::endl;
  43.  
  44.     // sanity check
  45.     std::cout.unsetf(my_num_put::reqFlags);
  46. 	std::cout                              << 0 << ' ' << 11 << std::endl;
  47.  
  48. 	return 0;
  49. }
Success #stdin #stdout 0s 3464KB
comments (?)
stdin 
Standard input is empty
stdout 
0 0xb
0x0 0xb
0 11
https://ideone.com/VGclTi
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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