Error Invalid ## usage expanding macro when token pasting string constant to user defined literal

[Bryn Edwards]

Simple example:

#define NUM_CHAR(str) str##_numch

inline auto operator "" _numch(const char *ch, std::size_t size) noexcept -> std:size_t
{
  return size;
}

int main(void)
{
  auto x = NUM_CHAR("abc");
}

Produces on Cppcheck 1.87 :
(error) failed to expand 'NUM_CHAR', Invalid ## usage when expanding 'NUM_CHAR'.

Expected behaviour is that this does not produce an error.

Running Cppcheck on the code with macro expanded does not produce any error:

inline auto operator "" _numch(const char *ch, std::size_t size) noexcept -> std:size_t
{
  return size;
}

int main(void)
{
  auto x = "abc"_numch;
}

Note that this only occurs for pasting string constants, the following does not produce any error:

#define HALF(num) num##_half

inline auto operator "" _half(long double num) noexcept -> long double
{
  return 0.5 * num;
}

int main(void)
{
  auto x = HALF(100.0);
}

[Bryn Edwards]

Looked into this briefly.
Appears to be an issue with simplecpp, rather than cppcheck.

[Daniel Marjamäki]

yes that sounds reasonable. simplecpp ensures that ## output is a valid token. Can you please report this in the simplecpp issue tracker: https://github.com/danmar/simplecpp/issues

I would assume that an invalidHashHash exception is thrown somewhere in expandHashHash: https://github.com/danmar/simplecpp/blob/master/simplecpp.cpp#L1798
Feel free to fix this.