[PATCH] build: disable default built-in rules and variables

[PATCH] build: disable default built-in rules and variables

[Doug Goldstein]

Disable the built-in rules and variables from GNU make to improve
build performance and avoid awkward corner cases with the built-in
rules. Currently none of the implicit rules are used but this is helpful
to do when developing changes to the build system.

Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
---
 xen/Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/xen/Makefile b/xen/Makefile
index fa9cf0a..3a1de99 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -15,6 +15,9 @@ export XEN_BUILD_HOST	?= $(shell hostname)
 export BASEDIR := $(CURDIR)
 export XEN_ROOT := $(BASEDIR)/..
 
+# Do not use make's built-in rules and variables
+MAKEFLAGS += -rR
+
 EFI_MOUNTPOINT ?= $(BOOT_DIR)/efi
 
 .PHONY: default
-- 
2.4.10

Re: [PATCH] build: disable default built-in rules and variables

[Andrew Cooper]

On 01/12/2015 21:19, Doug Goldstein wrote:
> Disable the built-in rules and variables from GNU make to improve
> build performance and avoid awkward corner cases with the built-in
> rules. Currently none of the implicit rules are used but this is helpful
> to do when developing changes to the build system.
>
> Signed-off-by: Doug Goldstein <cardoe@cardoe.com>

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

Trying this out, it reliably drops Xen's build time from ~58s to ~52s on
the dev box I have to hand.

~Andrew