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+# Generic Makefile Utilities
+
+###
+# Utility functions
+
+# Function: streq LHS RHS
+#
+# Return "true" if LHS == RHS, otherwise "".
+#
+# LHS == RHS <=> (LHS subst RHS is empty) and (RHS subst LHS is empty)
+streq = $(if $(1),$(if $(subst $(1),,$(2))$(subst $(2),,$(1)),,true),$(if $(2),,true))
+
+# Function: strneq LHS RHS
+#
+# Return "true" if LHS != RHS, otherwise "".
+strneq = $(if $(call streq,$(1),$(2)),,true)
+
+# Function: contains list item
+#
+# Return "true" if 'list' contains the value 'item'.
+contains = $(if $(strip $(foreach i,$(1),$(if $(call streq,$(2),$(i)),T,))),true,)
+
+# Function: is_subset a b
+# Return "true" if 'a' is a subset of 'b'.
+is_subset = $(if $(strip $(set_difference $(1),$(2))),,true)
+
+# Function: set_difference a b
+# Return a - b.
+set_difference = $(foreach i,$(1),$(if $(call contains,$(2),$(i)),,$(i)))
+
+# Function: Set variable value
+#
+# Set the given make variable to the given value.
+Set = $(eval $(1) := $(2))
+
+# Function: Append variable value
+#
+# Append the given value to the given make variable.
+Append = $(eval $(1) += $(2))
+
+# Function: IsDefined variable
+#
+# Check whether the given variable is defined.
+IsDefined = $(call strneq,undefined,$(flavor $(1)))
+
+# Function: IsUndefined variable
+#
+# Check whether the given variable is undefined.
+IsUndefined = $(call streq,undefined,$(flavor $(1)))
+
+# Function: VarOrDefault variable default-value
+#
+# Get the value of the given make variable, or the default-value if the variable
+# is undefined.
+VarOrDefault = $(if $(call IsDefined,$(1)),$($(1)),$(2))
+
+# Function: CheckValue variable
+#
+# Print the name, definition, and value of a variable, for testing make
+# utilities.
+#
+# Example:
+#   foo = $(call streq,a,a)
+#   $(call CheckValue,foo)
+# Example Output:
+#   CHECKVALUE: foo: $(call streq,,) - true
+CheckValue = $(info CHECKVALUE: $(1): $(value $(1)) - $($(1)))
+
+# Function: CopyVariable src dst
+#
+# Copy the value of the variable 'src' to 'dst', taking care to not define 'dst'
+# if 'src' is undefined. The destination variable must be undefined.
+CopyVariable = \
+  $(call AssertValue,$(call IsUndefined,$(2)),destination is already defined)\
+  $(if $(call IsUndefined,$(1)),,\
+       $(call Set,$(2),$($(1))))
+
+# Function: Assert value message
+#
+# Check that a value is true, or give an error including the given message
+Assert = $(if $(1),,\
+           $(error Assertion failed: $(2)))
+
+# Function: AssertEqual variable expected-value
+#
+# Check that the value of a variable is 'expected-value'.
+AssertEqual = \
+  $(if $(call streq,$($(1)),$(2)),,\
+       $(error Assertion failed: $(1): $(value $(1)) - $($(1)) != $(2)))
+
+# Function: CheckCommandLineOverrides list
+#
+# Check that all command line variables are in the given list. This routine is
+# useful for validating that users aren't trying to override something which
+# will not work.
+CheckCommandLineOverrides = \
+  $(foreach arg,$(MAKEOVERRIDES),\
+    $(call Set,varname,$(firstword $(subst =, ,$(arg)))) \
+    $(if $(call contains,$(1),$(varname)),,\
+      $(error "Invalid command line override: $(1) $(varname) (not supported)")))
+
+###
+# Clean up make behavior
+
+# Cancel all suffix rules. We don't want no stinking suffix rules.
+.SUFFIXES:
+
+###
+# Debugging
+
+# General debugging rule, use 'make print-XXX' to print the definition, value
+# and origin of XXX.
+make-print-%:
+	$(error PRINT: $(value $*) = "$($*)" (from $(origin $*)))