Re: [GIT PULL 2/2] Kconfig updates for v5.10-rc1

Linus Torvalds
2020-11-28T22:02:10Z

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On Fri, Nov 27, 2020 at 11:05 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> As for the cc1plus cost, I got a similar result.
>
> Running scripts/gcc-plugin.sh directly
> took me 0.5 sec, which is a fourth
> of the allmodconfig run-time.
>
> Actually, I did not know this shell script
> was so expensive to run...

So it turns out that one reason it's so expensive to run is that it
does a *lot* more than it claims to do.

It says "we need a c++ compiler that supports the designated
initializer GNU extension", but then it actually includes a header
file from hell, rather than just test designated initializers.

This patch makes the cc1plus overhead go down a lot. That said, I'm
doubtful we really want gcc plugins at all, considering that the only
real users have all apparently migrated to clang builtin functionality
instead.

Linus

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scripts/gcc-plugin.sh | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/gcc-plugin.sh b/scripts/gcc-plugin.sh
index b79fd0bea838..59db87bff456 100755
--- a/scripts/gcc-plugin.sh
+++ b/scripts/gcc-plugin.sh
@@ -8,8 +8,8 @@ srctree=$(dirname "$0")
gccplugins_dir=$($* -print-file-name=plugin)

# we need a c++ compiler that supports the designated initializer GNU extension
+test -e "$gccplugins_dir/include/plugin-version.h" &&
$HOSTCC -c -x c++ -std=gnu++98 - -fsyntax-only -I $srctree/gcc-plugins -I $gccplugins_dir/include 2>/dev/null <<EOF
-#include "gcc-common.h"
class test {
public:
int test;