Module Name: src
Committed By: rillig
Date: Fri Oct 23 17:53:01 UTC 2020
Modified Files:
src/usr.bin/make/unit-tests: varname-empty.exp varname-empty.mk
Log Message:
make(1): add tests for the variable named ""
To generate a diff of this commit:
cvs rdiff -u -r1.3 -r1.4 src/usr.bin/make/unit-tests/varname-empty.exp
cvs rdiff -u -r1.6 -r1.7 src/usr.bin/make/unit-tests/varname-empty.mk
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/usr.bin/make/unit-tests/varname-empty.exp
diff -u src/usr.bin/make/unit-tests/varname-empty.exp:1.3 src/usr.bin/make/unit-tests/varname-empty.exp:1.4
--- src/usr.bin/make/unit-tests/varname-empty.exp:1.3 Sat Aug 22 21:22:24 2020
+++ src/usr.bin/make/unit-tests/varname-empty.exp Fri Oct 23 17:53:01 2020
@@ -6,6 +6,8 @@ Var_Set("", "appended", ...) name expand
Var_Set("", "", ...) name expands to empty string - ignored
Var_Set("", "subst", ...) name expands to empty string - ignored
Var_Set("", "shell-output", ...) name expands to empty string - ignored
+Var_Set("${:U}", "assigned indirectly", ...) name expands to empty string - ignored
+Var_Set("", "assigned", ...) name expands to empty string - ignored
out: fallback
out: 1 2 3
exit status 0
Index: src/usr.bin/make/unit-tests/varname-empty.mk
diff -u src/usr.bin/make/unit-tests/varname-empty.mk:1.6 src/usr.bin/make/unit-tests/varname-empty.mk:1.7
--- src/usr.bin/make/unit-tests/varname-empty.mk:1.6 Thu Sep 24 06:03:44 2020
+++ src/usr.bin/make/unit-tests/varname-empty.mk Fri Oct 23 17:53:01 2020
@@ -1,4 +1,4 @@
-# $NetBSD: varname-empty.mk,v 1.6 2020/09/24 06:03:44 rillig Exp $
+# $NetBSD: varname-empty.mk,v 1.7 2020/10/23 17:53:01 rillig Exp $
#
# Tests for the special variable with the empty name.
#
@@ -16,22 +16,39 @@
# The only places where a variable is assigned a value are Var_Set and
# Var_Append, and these places protect the variable named "" from being
# defined. This is different from read-only variables, as that flag can
-# only apply to variables that are defined.
+# only apply to variables that are defined. The variable named "" must
+# never be defined though.
#
-# This is because it is heavily used in the .for loop expansion,
-# as well as to generate arbitrary strings, as in ${:Ufallback}.
+# See also:
+# The special variables @F or ^D, in var-class-local.mk
# Until 2020-08-22 it was possible to assign a value to the variable with
-# the empty name, leading to all kinds of unexpected effects.
-#
-# Before 2020-08-22, the simple assignment operator '=' had an off-by-one
-# bug that caused unrelated memory to be read in Parse_DoVar, invoking
-# undefined behavior.
+# the empty name, leading to all kinds of unexpected effects in .for loops
+# and other places that assume that ${:Ufallback} expands to "fallback".
+# The bug in Var_Set was that only expanded variables had been checked for
+# the empty name, but not the direct assignments with an empty name.
?= default
= assigned # undefined behavior until 2020-08-22
+= appended
:= subst
!= echo 'shell-output'
+.if ${:Ufallback} != "fallback"
+. error
+.endif
+
+${:U}= assigned indirectly
+.if ${:Ufallback} != "fallback"
+. error
+.endif
+
+# Before 2020-08-22, the simple assignment operator '=' after an empty
+# variable name had an off-by-one bug in Parse_DoVar. The code that was
+# supposed to "skip to operator character" started its search _after_ the
+# assignment operator, assuming that the variable name would be at least
+# one character long. It then looked for the next occurrence of a '=', which
+# could be several lines away or not occur at all. While looking for the
+# '=', some whitespace was nulled out, leading to out-of-bounds write.
+= assigned # undefined behavior until 2020-08-22
# The .for loop expands the expression ${i} to ${:U1}, ${:U2} and so on.
# This only works if the variable with the empty name is guaranteed to
