On Thu, 2019-02-28 at 16:18 -0700, Shaobo He wrote: > I can't afford a pdf version of the C standard. So I looked at the draft > version > used in the link I put in the commit message. It says (in 6.2.4:2), > > ``` > The lifetime of an object is the portion of program execution during which > storage is guaranteed to be reserved for it. An object exists, has a constant > address, and retains its last-stored value throughout its lifetime. If an > object > is referred to outside of its lifetime, the behavior is undefined. The value > of > a pointer becomes indeterminate when the object it points to (or just past) > reaches the end of its lifetime. > ``` > I couldn't find the definition of lifetime over a dynamically allocated > object > in the draft of C standard. I refer to this link > (https://en.cppreference.com/w/c/language/lifetime) which suggests that the > lifetime of an allocated object ends after the deallocation function is > called > upon it. > > I think maybe the more problematic issue is that the value of a freed pointer > is > intermediate.
In another section of the same draft I found the following: J.2 Undefined behavior [ ... ] The value of a pointer that refers to space deallocated by a call to the free or realloc function is used (7.22.3). Since the C standard explicitly refers to free() and realloc(), does that mean that that statement about undefined behavior does not apply to munmap() (for user space code) nor to kfree() (for kernel code)? Bart.
