GDCC-CC currently targets C11 compliance.

Unimplemented standard features

• Variable Length Arrays
• Complex numbers
• threads.h and stdatomic.h
• tgmath.h (_Generic is implemented, however)

Other quirks

• char/short/int are all 32-bit in ACS as the smallest addressable unit there is 32-bits. This is entirely permissible by the standard.
• C main is never called automatically. This isn't likely to be particularly useful in the context of game scripting.