Q: What are #pragmas and what are they good for?
A: The #pragma directive provides a single, well-defined ``escape hatch'' which can be used for all sorts of (nonportable) implementation-specific controls and extensions: source listing control, structure packing, warning suppression (like lint's old /* NOTREACHED */ comments), etc.
ISO Sec. 6.8.6
H&S Sec. 3.7 p. 61