From 28f8fb7d2b3fde2f5cbe5526ac4f1c932e3f5d26 Mon Sep 17 00:00:00 2001 From: Keir Fraser Date: Mon, 23 May 2011 17:38:28 +0100 Subject: [PATCH] Fix Config.mk's cc-option for -Wno-* options. These disable-warning options are handled specially by GCC: (a) they are ignored unless the compiler emits a warning; and (b) even then they produce a warning rather than an error To handle this, modify the test invocation of GCC to compile a fragment of code that will always provoke a warning (integer assigned to pointer). This works around (a) above. Then, we grep the compiler's stdout/stderr for the option-under-test, the presence of which would indicate an "unrecognized command-line option" warning/error. This works around (b) above, letting us distinguish between the "integer assigned to pointer" and "unrecognized command-line option" warnings. Signed-off-by: Keir Fraser --- Config.mk | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/Config.mk b/Config.mk index d57a6e4478..aa681aebd0 100644 --- a/Config.mk +++ b/Config.mk @@ -71,9 +71,19 @@ PYTHON_PREFIX_ARG ?= --prefix="$(PREFIX)" # https://bugs.launchpad.net/ubuntu/+bug/362570 # cc-option: Check if compiler supports first option, else fall back to second. +# +# This is complicated by the fact that unrecognised -Wno-* options: +# (a) are ignored unless the compilation emits a warning; and +# (b) even then produce a warning rather than an error +# To handle this we do a test compile, passing the option-under-test, on a code +# fragment that will always produce a warning (integer assigned to pointer). +# We then grep for the option-under-test in the compiler's output, the presence +# of which would indicate an "unrecognized command-line option" warning/error. +# # Usage: cflags-y += $(call cc-option,$(CC),-march=winchip-c6,-march=i586) -cc-option = $(shell if test -z "`$(1) $(2) -S -o /dev/null -xc \ - /dev/null 2>&1`"; then echo "$(2)"; else echo "$(3)"; fi ;) +cc-option = $(shell if test -z "`echo 'void*p=1;' | \ + $(1) $(2) -S -o /dev/null -xc - 2>&1 | grep -- $(2)`"; \ + then echo "$(2)"; else echo "$(3)"; fi ;) # cc-option-add: Add an option to compilation flags, but only if supported. # Usage: $(call cc-option-add CFLAGS,CC,-march=winchip-c6) -- 2.30.2