Compiling example code: 5-map.cc fail

[YuxinxinChen]

Hi,

This is a wonderful library I am looking for. However, when I am trying to compile the example code from the master branch, It fails with an error message:

5-map.cc:44:1: error: body of ‘constexpr’ function ‘constexpr const char* describe(Channel)’ not a return-statement
   44 | }
      | ^
make: *** [Makefile:20: 5-map.exe] Error 1

The g++ version I am using:

g++ (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Thanks!

-Yuxin

[aantron]

Thanks!

Does the example work if you remove this line from describe?

return "needed for gcc 5";

What is the command line you are using to compile the file? In particular, what language standard?

[QAbot-zh]

@aantron
I found the reason why the case failed to compile.
link
C++11's constexpr functions support exactly one return statement. The restriction was lifted in C++14.
So it doesn't work if only remove the final return line from describe in C++11.