Ada Programming/Pragmas/No Return
pragma No_Return (local_name);
No Return is a representation pragma for procedures, which states that a procedure will never return normally; that is, it will raise an exception, loop endlessly, or terminate the program (e.g. by means of an imported function like C’s exit or by triggering a hardware reset).
On the call site, this enables detection of dead code and suppression of warnings about missing return statements or missing assignment to variables.
The compiler ensures that a non-returning procedure will indeed not return by raising Program_Error if it would otherwise.
procedure P ( … ); pragma No_Return (P); procedure Q (out x: … ) is begin if Cond then P ( … ); Some_Thing_Else; -- This is dead code--and due to No_Return probably a compiler warning! else x := … ; end if; -- No warning about a missing assignment to x here end Q;
The pragma No_Return is standard in the language since Ada 2005. Some compilers (e.g. GNAT and AdaMagic) already recognised No_Return as implementation defined pragma before.
Ada Reference Manual
- AI95-00329 in Appendix: From: Tucker Taft, Sent: Tuesday, March 4, 2003 11:13 AM