What are the contents of the memory just allocated by `malloc()`?

Question

I was curious about what exactly a pointer holds, after malloc() was used to allocate memory space? The manpage tells me that calloc() initializes

Answer 1

No, malloc() returns uninitialized memory, the contents of which is indeterminate. So, attempt to use the value invokes undefined behavior.

Quoting C11, annex §J.2, Undefined behavior

The value of the object allocated by the malloc function is used

In this case, %s expects a null-terminated char array. However, the content of dynamic_chars is indeterminate, so there may very well be no null-terminator, at all, which will cause the out-of-bound memory access, which in turn invokes the UB.

Quoting C11, chapter §7.22.3.5, The malloc function (emphasis mine):

The malloc function allocates space for an object whose size is specified by size and whose value is indeterminate.

That said, please see this discussion on why not to cast the return value of malloc() and family in C..