Enrico Weigelt <weigelt@xxxxxxxx> writes: > * Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx> wrote: > >> Modifying an object via a const lvalue is a constraint violation; any >> program that does this is not a valid C program. > > Is the compiler able to use that for optimizations (eg. hold > const variables in registers, etc) ? It depends. Modifying an object via a const lvalue is invalid, but it is possible for the object to be modified in other ways. E.g., a const char* pointer may point to a value which is modified via a normal char* pointer. An object which is itself declared const may not be modified in any way, and the compiler does take advantage of that. >> Modifying a const object via a non-const lvalue is undefined behaviour. > > Is there a flag to forbid that ? -Wcast-qual -Werror. Ian
