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Diffstat (limited to 'contrib/bmake/unit-tests/var-class-cmdline.mk')
| -rw-r--r-- | contrib/bmake/unit-tests/var-class-cmdline.mk | 80 |
1 files changed, 0 insertions, 80 deletions
diff --git a/contrib/bmake/unit-tests/var-class-cmdline.mk b/contrib/bmake/unit-tests/var-class-cmdline.mk deleted file mode 100644 index 679e051bb242..000000000000 --- a/contrib/bmake/unit-tests/var-class-cmdline.mk +++ /dev/null @@ -1,80 +0,0 @@ -# $NetBSD: var-class-cmdline.mk,v 1.5 2021/02/23 21:59:31 rillig Exp $ -# -# Tests for variables specified on the command line. -# -# Variables that are specified on the command line override those from the -# global scope. -# -# For performance reasons, the actual implementation is more complex than the -# above single-sentence rule, in order to avoid unnecessary lookups in scopes, -# which before var.c 1.586 from 2020-10-25 calculated the hash value of the -# variable name once for each lookup. Instead, when looking up the value of -# a variable, the search often starts in the global scope since that is where -# most of the variables are stored. This conflicts with the statement that -# variables from the cmdline scope override global variables, since after the -# common case of finding a variable in the global scope, another lookup would -# be needed in the cmdline scope to ensure that there is no overriding -# variable there. -# -# Instead of this costly lookup scheme, make implements it in a different -# way: -# -# Whenever a global variable is created, this creation is ignored if -# there is a cmdline variable of the same name. -# -# Whenever a cmdline variable is created, any global variable of the -# same name is deleted. -# -# Whenever a global variable is deleted, nothing special happens. -# -# Deleting a cmdline variable is not possible. -# -# These 4 rules provide the guarantee that whenever a global variable exists, -# there cannot be a cmdline variable of the same name. Therefore, after -# finding a variable in the global scope, no additional lookup is needed in -# the cmdline scope. -# -# The above ruleset provides the same guarantees as the simple rule "cmdline -# overrides global". Due to an implementation mistake, the actual behavior -# was not entirely equivalent to the simple rule though. The mistake was -# that when a cmdline variable with '$$' in its name was added, a global -# variable was deleted, but not with the exact same name as the cmdline -# variable. Instead, the name of the global variable was expanded one more -# time than the name of the cmdline variable. For variable names that didn't -# have a '$$' in their name, it was implemented correctly all the time. -# -# The bug was added in var.c 1.183 on 2013-07-16, when Var_Set called -# Var_Delete to delete the global variable. Just two months earlier, in var.c -# 1.174 from 2013-05-18, Var_Delete had started to expand the variable name. -# Together, these two changes made the variable name be expanded twice in a -# row. This bug was fixed in var.c 1.835 from 2021-02-22. -# -# Another bug was the wrong assumption that "deleting a cmdline variable is -# not possible". Deleting such a variable has been possible since var.c 1.204 -# from 2016-02-19, when the variable modifier ':@' started to delete the -# temporary loop variable after finishing the loop. It was probably not -# intended back then that a side effect of this seemingly simple change was -# that both global and cmdline variables could now be undefined at will as a -# side effect of evaluating a variable expression. As of 2021-02-23, this is -# still possible. -# -# Most cmdline variables are set at the very beginning, when parsing the -# command line arguments. Using the special target '.MAKEFLAGS', it is -# possible to set cmdline variables at any later time. - -# A normal global variable, without any cmdline variable nearby. -VAR= global -.info ${VAR} - -# The global variable is "overridden" by simply deleting it and then -# installing the cmdline variable instead. Since there is no obvious way to -# undefine a cmdline variable, there is no need to remember the old value -# of the global variable could become visible again. -# -# See varmod-loop.mk for a non-obvious way to undefine a cmdline variable. -.MAKEFLAGS: VAR=makeflags -.info ${VAR} - -# If Var_SetWithFlags should ever forget to delete the global variable, -# the below line would print "global" instead of the current "makeflags". -.MAKEFLAGS: -V VAR |