Why are these constructs using pre and post-increment undefined behavior?

Why are these constructs using pre and post-increment undefined behavior?

c increment undefined-behavior operator-precedence sequence-points

c

Pointer expressions: ptr++, ++ptr and ++*ptr

c++ c pointers increment

c

Why does c = ++(a+b) give compilation error?

c increment

c

increment value of int being pointed to by pointer

c pointers increment post-increment

c

The difference between C and C++ regarding the ++ operator

c++ c increment prefix

c

Difference between i++ and (i)++ in C

c language-lawyer increment evaluation

c