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63 lines
2.2 KiB
Makefile
63 lines
2.2 KiB
Makefile
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# $NetBSD: directive-export-impl.mk,v 1.1 2020/12/29 01:45:06 rillig Exp $
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#
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# Test for the implementation of exporting variables to child processes.
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# This involves marking variables for export, actually exporting them,
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# or marking them for being re-exported.
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#
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# See also:
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# Var_Export
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# ExportVar
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# VarExportedMode (global)
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# VAR_EXPORTED (per variable)
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# VAR_REEXPORT (per variable)
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# VarExportMode (per call of Var_Export and ExportVar)
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: ${:U:sh} # side effect: initialize .SHELL
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.MAKEFLAGS: -dcpv
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# This is a variable that references another variable. At this point, the
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# other variable is still undefined.
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UT_VAR= <${REF}>
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# At this point, ExportVar("UT_VAR", VEM_PLAIN) is called. Since the
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# variable value refers to another variable, ExportVar does not actually
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# export the variable but only marks it as VAR_EXPORTED and VAR_REEXPORT.
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# After that, ExportVars registers the variable name in .MAKE.EXPORTED.
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# That's all for now.
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.export UT_VAR
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# Evaluating this expression shows the variable flags in the debug log,
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# which are VAR_EXPORTED|VAR_REEXPORT.
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: ${UT_VAR:N*}
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# At the last moment before actually forking off the child process for the
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# :!...! modifier, Cmd_Exec calls Var_ReexportVars to have all relevant
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# variables exported. Since this variable has both of the above-mentioned
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# flags set, it is actually exported to the environment. The variable flags
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# are not modified though, since the next time the :!...! modifier is
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# evaluated, the referenced variables could have changed, therefore the
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# variable will be exported anew for each ':sh' modifier, ':!...!' modifier,
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# '!=' variable assignment.
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.if ${:!echo "\$UT_VAR"!} != "<>"
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. error
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.endif
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# Evaluating this expression shows the variable flags in the debug log,
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# which are still VAR_EXPORTED|VAR_REEXPORT, which means that the variable
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# is still marked as being re-exported for each child process.
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: ${UT_VAR:N*}
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# Now the referenced variable gets defined. This does not influence anything
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# in the process of exporting the variable value, though.
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REF= defined
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# Nothing surprising here. The variable UT_VAR gets exported, and this time,
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# REF is defined and gets expanded into the exported environment variable.
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.if ${:!echo "\$UT_VAR"!} != "<defined>"
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. error
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.endif
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all:
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.MAKEFLAGS: -d0
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