8.19. .desc symbol, abs-expression

This directive sets the descriptor of the symbol (refer to Section 6.5 Symbol Attributes) to the low 16 bits of an absolute expression.

The .desc directive is not available when as is configured for COFF output; it is only for a.out or b.out object format. For the sake of compatibility, as accepts it, but produces no output, when configured for COFF.