a BSD make tool (derived from NetBSD’s make).
| cond-token-var.mk (bmake-20201101) | : | cond-token-var.mk (bmake-20201117) |
|---|
|
| # $NetBSD: cond-token-var.mk,v 1.4 2020/10/24 08:46:08 rillig Exp $ | | # $NetBSD: cond-token-var.mk,v 1.5 2020/11/15 14:58:14 rillig Exp $ |
| # | | # |
|
| # Tests for variables in .if conditions. | | # Tests for variable expressions in .if conditions. |
| | # |
| | # Note the fine distinction between a variable and a variable expression. |
| | # A variable has a name and a value. To access the value, one writes a |
| | # variable expression of the form ${VAR}. This is a simple variable |
| | # expression. Variable expressions can get more complicated by adding |
| | # variable modifiers such as in ${VAR:Mpattern}. |
| | # |
| | # XXX: Strictly speaking, variable modifiers should be called expression |
| | # modifiers instead since they only modify the expression, not the variable. |
| | # Well, except for the assignment modifiers, these do indeed change the value |
| | # of the variable. |
| | |
| DEF= defined | | DEF= defined |
| | |
| # A defined variable may appear on either side of the comparison. | | # A defined variable may appear on either side of the comparison. |
| .if ${DEF} == ${DEF} | | .if ${DEF} == ${DEF} |
| . info ok | | . info ok |
| .else | | .else |
| . error | | . error |
| .endif | | .endif |
| | |
| # A variable that appears on the left-hand side must be defined. | | # A variable that appears on the left-hand side must be defined. |
|
| | # The following line thus generates a parse error. |
| .if ${UNDEF} == ${DEF} | | .if ${UNDEF} == ${DEF} |
| . error | | . error |
| .endif | | .endif |
| | |
| # A variable that appears on the right-hand side must be defined. | | # A variable that appears on the right-hand side must be defined. |
|
| | # The following line thus generates a parse error. |
| .if ${DEF} == ${UNDEF} | | .if ${DEF} == ${UNDEF} |
| . error | | . error |
| .endif | | .endif |
| | |
| # A defined variable may appear as an expression of its own. | | # A defined variable may appear as an expression of its own. |
| .if ${DEF} | | .if ${DEF} |
| .endif | | .endif |
| | |
|
| # An undefined variable generates a warning. | | # An undefined variable on its own generates a parse error. |
| .if ${UNDEF} | | .if ${UNDEF} |
| .endif | | .endif |
| | |
|
| # The :U modifier turns an undefined variable into an ordinary expression. | | # The :U modifier turns an undefined expression into a defined expression. |
| | # Since the expression is defined now, it doesn't generate any parse error. |
| .if ${UNDEF:U} | | .if ${UNDEF:U} |
| .endif | | .endif |
| | | |
| End of changes. 6 change blocks. |
|---|
| 4 lines changed or deleted | | 18 lines changed or added |
|---|
"Fossies" - the Fresh Open Source Software Archive 