On 11.08.2023 15:48, Anthony PERARD wrote:
> On Wed, Jul 26, 2023 at 12:33:07PM +0200, Jan Beulich wrote:
>> In options like -march=, it may be only the sub-option which is
>> unrecognized by the compiler. In such an event the error message often
>> splits option and argument, typically saying something like "bad value
>> '<argument>' for '<option>'. Extend the grep invocation accordingly,
>> also accounting for Clang to not mention e.g. -march at all when an
>> incorrect argument was given for it.
>>
>> To keep things halfway readable, re-wrap and re-indent the entire
>> construct.
>>
>> Signed-off-by: Jan Beulich <jbeul...@suse.com>
>> ---
>> In principle -e "$$pat" could now be omitted from the grep invocation,
>> since if that matches, both $$opt and $$arg will, too. But I thought I'd
>> leave it for completeness.
>> ---
>> v3: Fix build with make 4.3 and newer, where the treatment of \# has
>> changed.
>> v2: Further relax grep patterns for clang, which doesn't mention -march
>> when complaining about an invalid argument to it.
>>
>> --- a/Config.mk
>> +++ b/Config.mk
>> @@ -8,6 +8,7 @@ endif
>> comma := ,
>> open := (
>> close := )
>> +sharp := \#
>> squote := '
>> #' Balancing squote, to help syntax highlighting
>> empty :=
>> @@ -90,9 +91,14 @@ PYTHON_PREFIX_ARG ?= --prefix="$(prefix)
>> # of which would indicate an "unrecognized command-line option"
>> warning/error.
>> #
>> # Usage: cflags-y += $(call cc-option,$(CC),-march=winchip-c6,-march=i586)
>> -cc-option = $(shell if test -z "`echo 'void*p=1;' | \
>> - $(1) $(2) -c -o /dev/null -x c - 2>&1 | grep --
>> $(2:-Wa$(comma)%=%) -`"; \
>> - then echo "$(2)"; else echo "$(3)"; fi ;)
>> +cc-option = $(shell pat='$(2:-Wa$(comma)%=%)'; \
>> + opt="$${pat%%=*}" arg="$${pat$(sharp)*=}"; \
>> + if test -z "`echo 'void*p=1;' | \
>> + $(1) $(2) -c -o /dev/null -x c - 2>&1 | \
>> + grep -e "$$pat" -e "$$opt" -e "$$arg" -`";
>> \
>> + then echo "$(2)"; \
>> + else echo "$(3)"; \
>> + fi;)
>
> This patch looks fine. Shouldn't the comment been updated as well? At
> the moment, it only discuss about -Wno-*, which it seems is why `grep`
> was introduced in the first place.
>
> But isn't it doing doing pattern matching on an error message going to
> lead sometime to false positive? Linux's build system seems to works
> fine by just using the exit value. They've got a few trick to deal with
> -Wno-* and with clang.
>
> For -Wno-$(warning), they test -W$(warning) instead. For clang, they've
> enable additional warnings:
> -Werror=unknown-warning-option
> -Werror=ignored-optimization-argument
> -Werror=option-ignored
> -Werror=unused-command-line-argument
I think using just -Werror is going to be enough. The completely changed
patch below appears to be doing fine, but of course requires me to drop
...
> In any case, the patch is fine.
> Reviewed-by: Anthony PERARD <anthony.per...@citrix.com>
... this.
Jan
--- a/Config.mk
+++ b/Config.mk
@@ -81,17 +81,17 @@ PYTHON_PREFIX_ARG ?= --prefix="$(prefix)
# cc-option: Check if compiler supports first option, else fall back to second.
#
-# This is complicated by the fact that unrecognised -Wno-* options:
+# This is complicated by the fact that with most gcc versions 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.
+# Further Clang also only warns for unrecognised -W* options. To handle this
+# we do a test compile, substituting -Wno-* by -W* and adding -Werror. This
+# way all unrecognised options are diagnosed uniformly, allowing us to merely
+# check exit status.
#
# Usage: cflags-y += $(call cc-option,$(CC),-march=winchip-c6,-march=i586)
-cc-option = $(shell if test -z "`echo 'void*p=1;' | \
- $(1) $(2) -c -o /dev/null -x c - 2>&1 | grep --
$(2:-Wa$(comma)%=%) -`"; \
+cc-option = $(shell if $(1) $(2:-Wno-%=-W%) -Werror -c -o /dev/null -x c
/dev/null >/dev/null 2>&1; \
then echo "$(2)"; else echo "$(3)"; fi ;)
# cc-option-add: Add an option to compilation flags, but only if supported.
