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  1. #include <iostream>
  2. #include <type_traits>
  3.  
  4. template<typename TF, typename Tag>
  5. void write_debug_output( std::ostream & out, TF&& f, Tag ) {
  6. 	out << f;
  7. }
  8.  
  9. struct tracer {
  10. 	template<typename T>
  11. 	struct tag { struct type {}; };
  12.  
  13. 	std::ostream & out;
  14. 	tracer( std::ostream & out, char const * file, int line )
  15. 		: out( out ) {
  16. 		out << file << ":" << line << ": ";
  17. 	}
  18. 	~tracer() {
  19. 		out << std::endl;
  20. 	}
  21.  
  22. 	template<typename TF, typename ... TR>
  23. 	void write( TF&& f, TR&& ... rest ) {
  24. 		typename tag<
  25. 			typename std::remove_cv<
  26. 				typename std::remove_reference<TF>::type
  27. 				>::type
  28. 			>::type t;
  29. 		write_debug_output( out, std::forward<TF>(f), t );
  30. 		out << " ";
  31. 		write( std::forward<TR>(rest)... );
  32. 	}
  33. 	template<typename TF>
  34. 	void write( TF&& f ) {
  35. 		typename tag<
  36. 			typename std::remove_cv<
  37. 				typename std::remove_reference<TF>::type
  38. 				>::type
  39. 			>::type t;
  40. 		write_debug_output( out, std::forward<TF>(f), t );
  41. 	}
  42. 	void write() {
  43. 		//handle the empty params case
  44. 	}
  45. };
  46.  
  47. #define TRACE(...) tracer( std::cout, __FILE__, __LINE__ ).write( __VA_ARGS__ )
  48.  
  49. #define TRACE_OUTPUT(match_type) \
  50. 	template<typename TF> \
  51. 	void write_debug_output( std::ostream & out, TF && f, tracer::tag<match_type>::type )
  52.  
  53. struct my_object { };
  54. TRACE_OUTPUT(my_object) {
  55. 	out << "my_object f is a " 
  56.  		<< (std::is_const<typename std::remove_reference<TF>::type>::value ? "const " : "" )
  57.  		<< (std::is_lvalue_reference<TF>::value ? "lvalue" : "rvalue");
  58. }
  59.  
  60. struct other_object {
  61. 	int val;
  62. };
  63. TRACE_OUTPUT(other_object) {
  64.  	out << "val=" << f.val;
  65. }
  66.  
  67. int main()
  68. {
  69.  	my_object const a;
  70. 	TRACE(a);
  71.  	TRACE("CONST",a);
  72.   	my_object b;
  73.   	TRACE("MUTABLE",b);
  74.  	TRACE("RVALUE", my_object() );
  75.  	TRACE( 123, 5.5 );
  76.  	TRACE();
  77.  	TRACE( "other", other_object{14} );
  78. }
  79.  
Success #stdin #stdout 0s 3300KB
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Standard input is empty
stdout
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prog.cpp:70: my_object f is a const lvalue
prog.cpp:71: CONST my_object f is a const lvalue
prog.cpp:73: MUTABLE my_object f is a lvalue
prog.cpp:74: RVALUE my_object f is a rvalue
prog.cpp:75: 123 5.5
prog.cpp:76: 
prog.cpp:77: other val=14
https://ideone.com/axWRoR
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
secret

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