#pragma unknown_control_flow (funcname[, funcname])
In order to describe procedures that alter the flow graphs of their callers, the C compiler provides the #pragma unknown_control_flow directive. Typically, this directive accompanies declarations of functions like setjmp(). On Sun systems, the include file <setjmp.h> contains the following:
extern int setjmp(); #pragma unknown_control_flow(setjmp)
Other functions with properties like those of setjmp() must be declared similarly.
In principle, an optimizer that recognizes this attribute could insert the appropriate edges in the control flow graph, thus handling function calls safely in functions that call setjmp(), while maintaining the ability to optimize code in unaffected parts of the flow graph.
The specified functions must be declared with a prototype or empty parameter list prior to this pragma.