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var-op-append.mk revision 1.11 
      1 # $NetBSD: var-op-append.mk,v 1.11 2023/11/02 05:14:58 rillig Exp $
      2 #
      3 # Tests for the '+=' variable assignment operator, which appends to a
      4 # variable, creating it if necessary.
      5 #
      6 # See also
      7 #	var-op.mk
      8 #
      9 # Standards
     10 #	The '+=' variable assignment operator is planned to be added in
     11 #	POSIX.1-202x.
     12 #
     13 #	This implementation does not support the immediate-expansion macros
     14 #	specified in POSIX.1-202x.  All variables are delayed-expansion.
     15 #
     16 # History
     17 #	The '+=' variable assignment operator was added before 1993-03-21.
     18 
     19 # Appending to an undefined variable is possible.
     20 # The variable is created, and no extra space is added before the value.
     21 VAR+=	one
     22 .if ${VAR} != "one"
     23 .  error
     24 .endif
     25 
     26 # Appending to an existing variable adds a single space and the value.
     27 VAR+=	two
     28 .if ${VAR} != "one two"
     29 .  error
     30 .endif
     31 
     32 # Appending an empty string nevertheless adds a single space.
     33 VAR+=	# empty
     34 .if ${VAR} != "one two "
     35 .  error
     36 .endif
     37 
     38 # Variable names may contain '+', and this character is also part of the
     39 # '+=' assignment operator.  As far as possible, the '+' is interpreted as
     40 # part of the assignment operator.
     41 #
     42 # See Parse_Var, AdjustVarassignOp.
     43 C++=	value
     44 .if ${C+} != "value" || defined(C++)
     45 .  error
     46 .endif
     47 
     48 # Before var.c 1.793 from 2021-02-03, the variable name of a newly created
     49 # variable was expanded two times in a row, which was unexpected but
     50 # irrelevant in practice since variable names containing dollars lead to
     51 # strange side effects in several other places as well.
     52 .MAKEFLAGS: -dv
     53 VAR.${:U\$\$\$\$\$\$\$\$}+=	dollars
     54 .MAKEFLAGS: -d0
     55 .if ${VAR.${:U\$\$\$\$\$\$\$\$}} != "dollars"
     56 .  error
     57 .endif
     58 
     59 all:
     60