Incorrect output for template code

[IOBYTE]

This code:

template<long Len = 128, long BlockSize = 128, class T = wchar_t>
class String {
public:
  bool Format(const wchar_t FormatStr[], ...) { return true; }
};

void FTest() {
  double d{};

  String s;
  s.Format(L"%i", d);
}

produced this output:

template<long Len = 128, long BlockSize = 128, class T = wchar_t>
class S

/* First instantiated from: insights.cpp:10 */
#ifdef INSIGHTS_USE_TEMPLATE
template<>
String -> String<128, 128, wchar_t>;
#endif
tring {
public:
  bool Format(const wchar_t FormatStr[], ...) { return true; }
};

/* First instantiated from: insights.cpp:10 */
#ifdef INSIGHTS_USE_TEMPLATE
template<>
class String<128, 128, wchar_t>
{
  
  public: 
  inline bool Format(const wchar_t * FormatStr, ...)
  {
    return true;
  }
  
  // inline constexpr String() noexcept = default;
};

#endif


void FTest()
{
  double d = {};
  String<128, 128, wchar_t> s = String<128, 128, wchar_t>();
  s.Format(L"%i", d);
}

The first instantiation was inserted in the middle of the class name on line 2.

[andreasfertig]

Hello @IOBYTE,

thanks for catching and reporting this issue! It looks like the deduction guide is the trouble maker here. A patch is on its way.

Andreas

[IOBYTE]

Thank you for the quick response.

I have a question about the output. Should it compile? The output on line 48 gives an error.

$ g++ -std=c++2a out.cpp
out.cpp:48:8: error: expected unqualified-id before ‘->’ token
   48 | String -> String<128, 128, wchar_t>;
      |        ^~
$ clang++ -std=c++20 out.cpp
out.cpp:48:8: error: cannot use arrow operator on a type
String -> String<128, 128, wchar_t>;
       ^
1 error generated.

[IOBYTE]

I forgot to mention that I added this as the first line of the output:
#define INSIGHTS_USE_TEMPLATE

[andreasfertig]

Hello @IOBYTE,

it is not supposed to compile. Deduction guides are still an element I'm fighting with. However, I think I can make the one in this example work. Thanks for bringing it up.

Andreas