Constant expression evaluates to -1 which cannot be narrowed to type 'char' [-Wc++11-narrowing]

[dereckson]

On Debian Sid (in armv7l / arm-linux-gnueabihf architecture), with clang 3.8.1-17:

./src/base64.h:41:11: error: constant expression evaluates to -1 which cannot be narrowed to type 'char' [-Wc++11-narrowing]
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
          ^~
./src/base64.h:41:11: note: insert an explicit cast to silence this issue
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
          ^~
          static_cast<char>( )

As there are too many of them, it stops the compilation (-ferror-limit=)

---

I can't repro on FreeBSD 11 (amd64) with clang 3.8.0 (compilation works). I can't repro either on Debian Jessie, gcc 4.9.2.

It's not tied to clang, as I can repro on the same Debian Sid arm machine with gcc:

In file included from src/base64.cpp:29:0:
src/base64.h:56:1: error: narrowing conversion of ‘-1’ from ‘int’ to ‘char’ inside { } [-Wnarrowing]
 };
 ^