C99 introduced the following keywords: _Bool_Complex_Imaginaryinlinerestrict
Why _Bool_Complex and _Imaginary instead of just boolcomplex and imaginary? To preserve backwards compatibility for existing codebases that might use boolcomplex or imaginary.
However, if that was a problem, why would that not have been a problem with inline and restrict too? How was C99 able to get away with adding those keywords directly rather than as _Underscored keywords?