237 lines
10 KiB
Makefile
237 lines
10 KiB
Makefile
# $NetBSD: var-scope-local.mk,v 1.5 2022/02/09 21:09:24 rillig Exp $
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#
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# Tests for target-local variables, such as ${.TARGET} or $@. These variables
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# are relatively short-lived as they are created just before making the
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# target. In contrast, global variables are typically created when the
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# makefiles are read in.
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#
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# The 7 built-in target-local variables are listed in the manual page. They
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# are defined just before the target is actually made. Additional
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# target-local variables can be defined in dependency lines like
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# 'target: VAR=value', one at a time.
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.MAIN: all
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# The target-local variables can be used in expressions, just like other
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# variables. When these expressions are evaluated outside of a target, these
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# expressions are not yet expanded, instead their text is preserved, to allow
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# these expressions to expand right in time when the target-local variables
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# are actually set.
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#
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# Conditions from .if directives are evaluated in the scope of the command
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# line, which means that variables from the command line, from the global
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# scope and from the environment are resolved, in this order (but see the
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# command line option '-e'). In that phase, expressions involving
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# target-local variables need to be preserved, including the exact names of
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# the variables.
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#
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# Each of the built-in target-local variables has two equivalent names, for
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# example '@' is equivalent to '.TARGET'. The implementation might
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# canonicalize these aliases at some point, and that might be surprising.
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# This aliasing happens for single-character variable names like $@ or $<
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# (see VarFind, CanonicalVarname), but not for braced or parenthesized
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# expressions like ${@}, ${.TARGET} ${VAR:Mpattern} (see Var_Parse,
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# ParseVarname).
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#
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# In the following condition, make expands '$@' to the long-format alias
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# '$(.TARGET)'; note that the alias is not written with braces, as would be
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# common in BSD makefiles, but with parentheses. This alternative spelling
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# behaves the same though.
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.if $@ != "\$\(.TARGET)"
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. error
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.endif
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# In the long form of writing a target-local variable, the text of the
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# expression is preserved exactly as written, no matter whether it is written
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# with '{' or '('.
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.if ${@} != "\$\{@}"
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. error
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.endif
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.if $(@) != "\$\(@)"
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. error
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.endif
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# If the variable expression contains modifiers, the behavior depends on the
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# actual modifiers. The modifier ':M' keeps the expression in the state
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# 'undefined'. Since the expression is still undefined after evaluating all
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# the modifiers, the value of the expression is discarded and the expression
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# text is used instead. This preserves the expressions based on target-local
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# variables as long as possible.
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.if ${@:M*} != "\$\{@:M*}"
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. error
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.endif
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# In the following examples, the expressions are based on target-local
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# variables but use the modifier ':L', which turns an undefined expression
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# into a defined one. At the end of evaluating the expression, the state of
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# the expression is not 'undefined' anymore. The value of the expression
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# is the name of the variable, since that's what the modifier ':L' does.
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.if ${@:L} != "@"
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. error
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.endif
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.if ${.TARGET:L} != ".TARGET"
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. error
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.endif
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.if ${@F:L} != "@F"
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. error
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.endif
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.if ${@D:L} != "@D"
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. error
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.endif
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# Additional target-local variables may be defined in dependency lines.
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.MAKEFLAGS: -dv
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# In the following line, the ':=' may either be interpreted as an assignment
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# operator or as the dependency operator ':', followed by an empty variable
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# name and the assignment operator '='. It is the latter since in an
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# assignment, the left-hand side must be at most a single word. The empty
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# variable name is expanded twice, once for 'one' and once for 'two'.
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# expect: Var_SetExpand: variable name "" expands to empty string, with value "three" - ignored
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# expect: Var_SetExpand: variable name "" expands to empty string, with value "three" - ignored
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one two:=three
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# If the two targets to the left are generated by a variable expression, the
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# line is parsed as a variable assignment since its left-hand side is a single
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# word.
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# expect: Global: one two = three
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${:Uone two}:=three
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.MAKEFLAGS: -d0
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.SUFFIXES: .c .o
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# One of the dynamic target-local variables is '.TARGET'. Since this is not
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# a suffix transformation rule, the variable '.IMPSRC' is not defined.
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# expect: : Making var-scope-local.c out of nothing.
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var-scope-local.c:
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: Making ${.TARGET} ${.IMPSRC:Dfrom ${.IMPSRC}:Uout of nothing}.
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# This is a suffix transformation rule, so both '.TARGET' and '.IMPSRC' are
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# defined.
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# expect: : Making var-scope-local.o from var-scope-local.c.
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# expect: : Making basename "var-scope-local.o" in "." from "var-scope-local.c" in ".".
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.c.o:
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: Making ${.TARGET} from ${.IMPSRC}.
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# The local variables @F, @D, <F, <D are legacy forms.
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# See the manual page for details.
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: Making basename "${@F}" in "${@D}" from "${<F}" in "${<D}".
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# expect: : all overwritten
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all: var-scope-local.o
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# The ::= modifier overwrites the .TARGET variable in the node
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# 'all', not in the global scope. This can be seen with the -dv
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# option, looking for "all: @ = overwritten".
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: ${.TARGET} ${.TARGET::=overwritten}${.TARGET}
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# Begin tests for custom target-local variables, for all 5 variable assignment
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# operators.
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all: var-scope-local-assign.o
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all: var-scope-local-append.o
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all: var-scope-local-append-global.o
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all: var-scope-local-default.o
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all: var-scope-local-subst.o
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all: var-scope-local-shell.o
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var-scope-local-assign.o \
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var-scope-local-append.o \
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var-scope-local-append-global.o \
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var-scope-local-default.o \
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var-scope-local-subst.o \
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var-scope-local-shell.o:
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: Making ${.TARGET} with VAR="${VAR}".
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# Target-local variables are enabled by default. Force them to be enabled
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# just in case a test above has disabled them.
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.MAKE.TARGET_LOCAL_VARIABLES= yes
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VAR= global
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# If the sources of a dependency line look like a variable assignment, make
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# treats them as such. There is only a single variable assignment per
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# dependency line, which makes whitespace around the assignment operator
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# irrelevant.
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#
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# expect-reset
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# expect: : Making var-scope-local-assign.o with VAR="local".
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var-scope-local-assign.o: VAR= local
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# Assignments using '+=' do *not* look up the global value, instead they only
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# look up the variable in the target's own scope.
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var-scope-local-append.o: VAR+= local
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# Once a variable is defined in the target-local scope, appending using '+='
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# behaves as expected. Note that the expression '${.TARGET}' is not resolved
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# when parsing the dependency line, its evaluation is deferred until the
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# target is actually made.
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# expect: : Making var-scope-local-append.o with VAR="local to var-scope-local-append.o".
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var-scope-local-append.o: VAR += to ${.TARGET}
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# To access the value of a global variable, use a variable expression. This
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# expression is expanded before parsing the whole dependency line. Since the
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# expansion happens to the right of the dependency operator ':', the expanded
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# text does not influence parsing of the dependency line. Since the expansion
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# happens to the right of the assignment operator '=', the expanded text does
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# not influence the parsing of the variable assignment. The effective
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# variable assignment, after expanding the whole line first, is thus
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# 'VAR= global+local'.
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# expect: : Making var-scope-local-append-global.o with VAR="global+local".
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var-scope-local-append-global.o: VAR= ${VAR}+local
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var-scope-local-default.o: VAR ?= first
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var-scope-local-default.o: VAR ?= second
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# XXX: '?=' does look at the global variable. That's a long-standing
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# inconsistency between the assignment operators '+=' and '?='. See
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# Var_AppendExpand and VarAssign_Eval.
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# expect: : Making var-scope-local-default.o with VAR="global".
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# Using the variable assignment operator ':=' provides another way of
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# accessing a global variable and extending it with local modifications. The
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# '$' has to be written as '$$' though to survive the expansion of the
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# dependency line as a whole. After that, the parser sees the variable
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# assignment as 'VAR := ${VAR}+local' and searches for the variable 'VAR' in
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# the usual scopes, picking up the variable from the global scope.
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# expect: : Making var-scope-local-subst.o with VAR="global+local".
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var-scope-local-subst.o: VAR := $${VAR}+local
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# The variable assignment operator '!=' assigns the output of the shell
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# command, as everywhere else. The shell command is run when the dependency
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# line is parsed.
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var-scope-local-shell.o: VAR != echo output
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# While VAR=use will be set for a .USE node, it will never be seen since only
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# the ultimate target's context is searched; the variable assignments from the
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# .USE target are not copied to the ultimate target's.
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# expect: : var-scope-local-use.o uses .USE VAR="global"
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a_use: .USE VAR=use
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: ${.TARGET} uses .USE VAR="${VAR}"
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all: var-scope-local-use.o
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var-scope-local-use.o: a_use
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# Since parse.c 1.656 from 2022-01-27 and before parse.c 1.662 from
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# 2022-02-05, there was an out-of-bounds read in Parse_IsVar when looking for
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# a variable assignment in a dependency line with trailing whitespace. Lines
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# without trailing whitespace were not affected. Global variable assignments
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# were guaranteed to have no trailing whitespace and were thus not affected.
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#
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# Try to reproduce some variants that may lead to a crash, depending on the
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# memory allocator. To get a crash, the terminating '\0' of the line must be
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# the last byte of a memory page. The expression '${:U}' forces this trailing
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# whitespace.
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# On FreeBSD x86_64, a crash could in some cases be forced using the following
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# line, which has length 47, so the terminating '\0' may end up at an address
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# of the form 0xXXXX_XXXX_XXXX_Xfff:
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Try_to_crash_FreeBSD.xxxxxxxxxxxxxxxxxx: 12345 ${:U}
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# The following line has length 4095, so line[4095] == '\0'. If the line is
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# allocated on a page boundary and the following page is not mapped, this line
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# leads to a segmentation fault.
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${:U:range=511:@_@1234567@:ts.}: 12345 ${:U}
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# The following line has length 8191, so line[8191] == '\0'. If the line is
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# allocated on a page boundary and the following page is not mapped, this line
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# leads to a segmentation fault.
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${:U:range=1023:@_@1234567@:ts.}: 12345 ${:U}
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12345:
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