bmake/unit-tests/var-scope-cmdline.mk

11 # variable name once for each lookup.  Instead, when looking up the value of
12 # a variable, the search often starts in the global scope since that is where
15 # common case of finding a variable in the global scope, another lookup would
17 # variable there.
22 #	Whenever a global variable is created, this creation is ignored if
23 #	there is a cmdline variable of the same name.
25 #	Whenever a cmdline variable is created, any global variable of the
28 #	Whenever a global variable is deleted, nothing special happens.
30 #	Deleting a cmdline variable is not possible.
32 # These 4 rules provide the guarantee that whenever a global variable exists,
33 # there cannot be a cmdline variable of the same name.  Therefore, after
34 # finding a variable in the global scope, no additional lookup is needed in
40 # that when a cmdline variable with '$$' in its name was added, a global
41 # variable was deleted, but not with the exact same name as the cmdline
42 # variable.  Instead, the name of the global variable was expanded one more
43 # time than the name of the cmdline variable.  For variable names that didn't
47 # Var_Delete to delete the global variable.  Just two months earlier, in var.c
48 # 1.174 from 2013-05-18, Var_Delete had started to expand the variable name.
49 # Together, these two changes made the variable name be expanded twice in a
52 # Another bug was the wrong assumption that "deleting a cmdline variable is
53 # not possible".  Deleting such a variable has been possible since var.c 1.204
54 # from 2016-02-19, when the variable modifier ':@' started to delete the
55 # temporary loop variable after finishing the loop.  It was probably not
69 # A normal global variable, without any cmdline variable nearby.
74 # The global variable is "overridden" by simply deleting it and then
75 # installing the cmdline variable instead.  Since there is no obvious way to
76 # undefine a cmdline variable, there is no need to remember the old value
77 # of the global variable could become visible again.
79 # See varmod-loop.mk for a non-obvious way to undefine a cmdline variable.
84 # If Var_SetWithFlags should ever forget to delete the global variable,