What sense do these clobbered variable warnings make?

Question

I have a function like this:

#include 
jmp_buf buf;
void func2(int g);
extern int some_global;
void func(int x)
{
    if (setjmp(buf))
               


        

Answer 1

From man longjmp:

The values of automatic variables are unspecified after a call to longjmp() if they meet all the following criteria:

   ·  they are local to the function that made the corresponding setjmp(3)
      call;

   ·  their  values  are  changed  between  the  calls  to  setjmp(3)  and
      longjmp(); and

   ·  they are not declared as volatile.

As it happens, your x variable in the first example meets the criteria:

• It is local to the function, as function parameters are just like local automatic variables.
• Its value may be changed just after setjmp if some_global is true.
• It is not volatile.

So its value may be unspecified (clobbered).

About why the second version does not emit the warning... no idea.