From: Masahiro Yamada masahiroy@kernel.org
commit 1e860048c53ee77ee9870dcce94847a28544b753 upstream.
Linus pointed out a third of the time in the Kconfig parse stage comes from the single invocation of cc1plus in scripts/gcc-plugin.sh [1], and directly testing plugin-version.h for existence cuts down the overhead a lot. [2]
This commit takes one step further to kill the build test entirely.
The small piece of code was probably intended to test the C++ designated initializer, which was not supported until C++20.
In fact, with -pedantic option given, both GCC and Clang emit a warning.
$ echo 'class test { public: int test; } test = { .test = 1 };' | g++ -x c++ -pedantic - -fsyntax-only <stdin>:1:43: warning: C++ designated initializers only available with '-std=c++2a' or '-std=gnu++2a' [-Wpedantic] $ echo 'class test { public: int test; } test = { .test = 1 };' | clang++ -x c++ -pedantic - -fsyntax-only <stdin>:1:43: warning: designated initializers are a C++20 extension [-Wc++20-designator] class test { public: int test; } test = { .test = 1 }; ^ 1 warning generated.
Otherwise, modern C++ compilers should be able to build the code, and hopefully skipping this test should not make any practical problem.
Checking the existence of plugin-version.h is still needed to ensure the plugin-dev package is installed. The test code is now small enough to be embedded in scripts/gcc-plugins/Kconfig.
[1] https://lore.kernel.org/lkml/CAHk-=wjU4DCuwQ4pXshRbwDCUQB31ScaeuDo1tjoZ0_Pjh... [2] https://lore.kernel.org/lkml/CAHk-=whK0aQxs6Q5ijJmYF1n2ch8cVFSUzU5yUM_HOjig=...
Reported-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Masahiro Yamada masahiroy@kernel.org Signed-off-by: Kees Cook keescook@chromium.org Link: https://lore.kernel.org/r/20201203125700.161354-1-masahiroy@kernel.org Cc: Thomas Lindroth thomas.lindroth@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- scripts/gcc-plugin.sh | 19 ------------------- scripts/gcc-plugins/Kconfig | 2 +- 2 files changed, 1 insertion(+), 20 deletions(-) delete mode 100755 scripts/gcc-plugin.sh
--- a/scripts/gcc-plugin.sh +++ /dev/null @@ -1,19 +0,0 @@ -#!/bin/sh -# SPDX-License-Identifier: GPL-2.0 - -set -e - -srctree=$(dirname "$0") - -gccplugins_dir=$($* -print-file-name=plugin) - -# we need a c++ compiler that supports the designated initializer GNU extension -$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; -} test = { - .test = 1 -}; -EOF --- a/scripts/gcc-plugins/Kconfig +++ b/scripts/gcc-plugins/Kconfig @@ -9,7 +9,7 @@ menuconfig GCC_PLUGINS bool "GCC plugins" depends on HAVE_GCC_PLUGINS depends on CC_IS_GCC - depends on $(success,$(srctree)/scripts/gcc-plugin.sh $(CC)) + depends on $(success,test -e $(shell,$(CC) -print-file-name=plugin)/include/plugin-version.h) default y help GCC plugins are loadable modules that provide extra features to the