Otherwise -Wstrict-prototypes now emits the following warnings:
mini-dtls-large.c:30:5: error: function declaration isn't a prototype [-Werror=strict-prototypes]
30 | int main()
| ^~~~
mini-dtls-large.c: In function 'main':
mini-dtls-large.c:30:5: error: old-style function definition [-Werror=old-style-definition]
cc1: all warnings being treated as errors