Specify signed char

[tasleson]

Addresses #1939

x86 architecture default to signed characters. Other architectures
default to unsigned characters. When building on non-x86 arch we
get the following error

./json.hpp:22700:42:   required from here
./json.hpp:8494:24: error: comparison is always true due to limited
                           range of data type [-Werror=type-limits]
 8494 |             if ('\x00' <= c and c <= '\x1F')
      |                 ~~~~~~~^~~~

Signed-off-by: Tony Asleson [email protected]

[jaredgrubb]

Hmm, not sure if that's the best fix. Maybe change the condition to if (static_cast<unsigned char>(c) <= '\x1F')?

[coveralls]

Coverage remained the same at 100.0% when pulling 3c3c11a on tasleson:specify_sign into 973c52d on nlohmann:develop.

[nlohmann]

We may use SFINAE to decide between a signed char and an unsigned char version. Changing everything internally to signed char seems odd.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[nlohmann]

I do not like this change just to fix a type-limits warning. The must be a better way.