#pragma unknown_control_flow (funcname[, funcname])
To describe procedures that alter the flow graphs of their callers, use the #pragma unknown_control_flow directive. Typically, this directive accompanies declarations of functions like setjmp(). On Oracle Solaris systems, the include file <setjmp.h> contains the following code:
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.