7.13 Nonlocal jumps <setjmp.h>

• 7.13.1 Save calling environment
  • 7.13.1.1 The setjmp macro
• 7.13.2 Restore calling environment
  • 7.13.2.1 The longjmp function

1

The header <setjmp.h> defines the macro setjmp, and declares one function and one type, for bypassing the normal function call and return discipline.[1]

2

The type declared is

jmp_buf

which is an array type suitable for holding the information needed to restore a calling environment. The environment of a call to the setjmp macro consists of information sufficient for a call to the longjmp function to return execution to the correct block and invocation of that block, were it called recursively. It does not include the state of the floating-point status flags, of open files, or of any other component of the abstract machine.

3

It is unspecified whether setjmp is a macro or an identifier declared with external linkage. If a macro definition is suppressed in order to access an actual function, or a program defines an external identifier with the name setjmp, the behavior is undefined.

Footnotes

[1]

These functions are useful for dealing with unusual conditions encountered in a low-level function of a program.