C90 Compliance

I'm trying to get another library (https://github.com/redis/hiredis) to compile with an app that is shooting for C89/C90 compliance. I'm running into problems. It uses sds.

The errors in sds that are preventing compilation are things like the following:

sds.h:48:10: warning: ISO C90 does not support flexible array members [-Wpedantic]
char buf[];

sds.h:86:8: error: unknown type name ‘inline’
static inline size_t sdslen(const sds s) {

sds.c:640:52: warning: ISO C90 does not support ‘long long’ [-Wlong-long]

Is there any chance that sds (being a low level library) can be changed to become C90 compliant?

Related Issue:
https://github.com/redis/hiredis/issues/494