directive-ifdef.mk revision 1.5
1 1.5 rillig # $NetBSD: directive-ifdef.mk,v 1.5 2022/01/23 21:48:59 rillig Exp $ 2 1.1 rillig # 3 1.5 rillig # Tests for the .ifdef directive, which evaluates bare words by calling 4 1.5 rillig # 'defined(word)'. 5 1.1 rillig 6 1.5 rillig DEFINED= defined 7 1.5 rillig 8 1.5 rillig # There is no variable named 'UNDEF', therefore the condition evaluates to 9 1.5 rillig # false. 10 1.5 rillig .ifdef UNDEF 11 1.5 rillig . error 12 1.5 rillig .endif 13 1.5 rillig 14 1.5 rillig # There is a variable named 'DEFINED', so the condition evaluates to true. 15 1.5 rillig .ifdef DEFINED 16 1.5 rillig .else 17 1.5 rillig . error 18 1.5 rillig .endif 19 1.1 rillig 20 1.5 rillig # Since a bare word is an abbreviation for 'defined(word)', these can be 21 1.5 rillig # used to construct complex conditions. 22 1.5 rillig .ifdef UNDEF && DEFINED 23 1.5 rillig . error 24 1.5 rillig .endif 25 1.5 rillig .ifdef UNDEF || DEFINED 26 1.5 rillig .else 27 1.5 rillig . error 28 1.5 rillig .endif 29 1.3 rillig 30 1.3 rillig # It looks redundant to have a call to defined() in an .ifdef, but it's 31 1.5 rillig # possible. The '.ifdef' only affects bare words, not function calls. 32 1.3 rillig .ifdef defined(DEFINED) 33 1.3 rillig .else 34 1.3 rillig . error 35 1.3 rillig .endif 36 1.3 rillig 37 1.5 rillig # String literals are handled the same in all variants of the '.if' directive, 38 1.5 rillig # they evaluate to true if they are not empty, therefore this particular 39 1.5 rillig # example looks confusing and is thus not found in practice. 40 1.4 rillig .ifdef "" 41 1.4 rillig . error 42 1.4 rillig .else 43 1.4 rillig .endif 44 1.4 rillig 45 1.5 rillig # Whitespace counts as non-empty as well. 46 1.4 rillig .ifdef " " 47 1.4 rillig .else 48 1.4 rillig . error 49 1.4 rillig .endif 50 1.4 rillig 51 1.5 rillig all: .PHONY 52
Indexes created Thu Oct 02 10:09:58 GMT 2025