Improve error reporting

[aremmell]

Thanks for the library. I'm now using it to load and save configuration files in an IoT Linux service.

I have made some small additions I think you will find useful (feel free to disregard if not!):

1. Add function json_strerror. Takes an int return value from any other function in the library and returns a const char* of the human-readable error message for that code (or '<unknown>' if it isn't a known error code).
2. Add function json_perror. Calls json_strerror and outputs the message to stderr.

All of my changes can be disabled by uncommenting the #define JSON_NO_ERRORMSG line I added to json.h. I did this in case memory constraints are a concern.

These functions are intended to be in the spirit of the POSIX strerror and perror functions.

Cheers,
Ryan

[aremmell]

Another suggested improvement would be to add a global to store the 'last error' for the calling thread, and then remove the int parameter from these functions and instead add a new function called json_geterror.

[NicolasDP]

Just to be consistent, the indentation in the file is tabulation.

[NicolasDP]

I think it is a very useful addition to the library. However, the maintainer of this repo might wish you to replace your 4 space indentation by a tabulation (in both json.c and json.h) to remain consistent.

Also, somehow, the permission settings on the files have been changed from 644 to 744 (with execution rights on it).

[aremmell]

Thanks, @NicolasDP

I wrote this in a git repo on an NFS mount on the IoT board hence the permissions (the mount needs to be accessible to world since the remote users aren’t known).

I can/will fix that and the indentation if desired.

Cheers

[aremmell]

lol @ me. I did that probably the worst way possible and I think I just caught back up. Never code without food.

Anyway, it turns out some of the formatting was using spaces, so that lead to much confusion on my part trying to read diffs.

I think it should be good now, though. And the permissions should be good as well.