fix warnings showing up with -Wall

[andresy]

Proposed changes

Fix all warnings occurring when compiling with -Wall

Checklist

Put an x in the boxes that apply.

• [x ] I have read the CONTRIBUTING document
• [ x] I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• [ x] I have added tests that prove my fix is effective or that my feature works
• [ x] I have updated the necessary documentation (if needed)

[awni]

This is awesome, thanks! What do you think about adding -Wall as a build option by default so we stay warning free (that way it will be checked in circle).

[andresy]

I think with clang it would make sense.

With gcc one get a lot more warnings -- (possibly what you would get with -Wall -Wextra with clang), so I think we would not want to have this option enabled right now for gcc.

These warnings you get with gcc include type mismatch warnings (say a int for loop, with a size_t limit). I did not fix these yet, I was actually not sure we want to fix them

[awni]

LGTM