const qualifier mismatch warnings

[obones]

This is a spin off from #1866 as I believe it requires a bit of discussion.

Compiling with VS2019, I get those three warnings:

File	Line	Code	Message
data_tag.c	234	C4090	'function': different 'const' qualifiers
r_api.c	923	C4090	'function': different 'const' qualifiers
rtl_433.c	1431	C4090	'function': different 'const' qualifiers

They all come from a line that calls the free method to free memory allocated earlier. But the argument given to free is always a char const ** when the method expects a non const pointer.

Could it be that the const keyword is wrongly placed in the variable/return type declaration? I must admit that I'm always a bit confused by the possible positions of the const keyword and their respective meanings.

Any suggestion is most welcome

[zuckschwerdt]

I follow the handy rule to read types right-to-left, so a pointer to a pointer to const-chars. These instances are arrays of char const *. The contents must never be touched or free'd but the array itself is short-lived heap memory.

[gdt]

Is this still a problem with current code?

[obones]

This appears to have been fixed by d67ee96