Undefined behavior: when attempting to access the result of function call

Question

The following compiles and prints \"string\" as an output.

#include 

struct S { int x; char c[7]; };

struct S bar() {
    struct S s = {42,          


        

Answer 1

The sequence point occurs at the end of the full expression- i.e., when printf returns in this example. There are other cases where sequence points occur

Effectively, this rule states that function temporaries do not live beyond the next sequence point- which in this case, occurs well after it's use, so your program has quite well-defined behaviour.

Here's a simple example of not well-defined behaviour:

char* c = bar().c; *c = 5; // UB

Here, the sequence point is met after c is created, and the memory it points to is destroyed, but we then attempt to access c, resulting in UB.