[Qemu-devel] [PATCH 1/3] rules.mak: New logical functions for handling y/n values

[Peter Maydell <peter.maydell@linaro.org>]

Add new logical functions for handling y/n values like those we
use in CONFIG_FOO variables:
 lnot : logical NOT
 land : logical AND
 lor : logical OR
 eq : equality
 ne : non-equality
 lif : like Make's $(if) but with an eq-like test

and a couple of utility functions:
 isempty : true if argument is empty
 notempty : true if argument is not empty

Based on an idea by Ákos Kovács <akoskovacs@gmx.com>.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 rules.mak |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/rules.mak b/rules.mak
index abc2e84..ccbf0e3 100644
--- a/rules.mak
+++ b/rules.mak
@@ -89,6 +89,24 @@ find-in-path = $(if $(find-string /, $1), \
         $(wildcard $1), \
         $(wildcard $(patsubst %, %/$1, $(subst :, ,$(PATH)))))
 
+# Logical functions (for operating on y/n values like CONFIG_FOO vars)
+# Inputs to these must be either "y" (true) or "n" or "" (both false)
+# Output is always either "y" or "n".
+# Usage: $(call land,$(CONFIG_FOO),$(CONFIG_BAR))
+# Logical NOT
+lnot = $(if $(subst n,,$1),n,y)
+# Logical AND
+land = $(if $(findstring yy,$1$2),y,n)
+# Logical OR
+lor = $(if $(findstring y,$1$2),y,n)
+# Comparison: note that "n" is eq to "".
+eq = $(if $(filter $(call lnot,$1),$(call lnot,$2)),y,n)
+ne = $(if $(filter $(call lnot,$1),$(call lnot,$2)),n,y)
+
+# Returns "y" or "n" depending on whether input argument is the empty string
+isempty = $(if $1,n,y)
+notempty = $(if $1,y,n)
+
 # Generate files with tracetool
 TRACETOOL=$(PYTHON) $(SRC_PATH)/scripts/tracetool.py
 
-- 
1.7.9.5