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* [PATCH] gcc-plugins: simplify GCC plugin-dev capability test
@ 2020-12-03 12:57 Masahiro Yamada
  2020-12-03 17:37 ` Linus Torvalds
                   ` (3 more replies)
  0 siblings, 4 replies; 18+ messages in thread
From: Masahiro Yamada @ 2020-12-03 12:57 UTC (permalink / raw)
  To: linux-kbuild, Kees Cook, Emese Revfy, linux-hardening
  Cc: Linus Torvalds, Masahiro Yamada, Nathan Chancellor,
	Nick Desaulniers, clang-built-linux, linux-kernel

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_PjhLHzQ@mail.gmail.com/
[2] https://lore.kernel.org/lkml/CAHk-=whK0aQxs6Q5ijJmYF1n2ch8cVFSUzU5yUM_HOjig=+vnw@mail.gmail.com/

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.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

diff --git a/scripts/gcc-plugin.sh b/scripts/gcc-plugin.sh
deleted file mode 100755
index b79fd0bea838..000000000000
--- 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
diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
index ae19fb0243b9..ab9eb4cbe33a 100644
--- 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
-- 
2.27.0


^ permalink raw reply related	[flat|nested] 18+ messages in thread

end of thread, other threads:[~2021-01-19 21:27 UTC | newest]

Thread overview: 18+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-12-03 12:57 [PATCH] gcc-plugins: simplify GCC plugin-dev capability test Masahiro Yamada
2020-12-03 17:37 ` Linus Torvalds
2020-12-04 22:02 ` Kees Cook
2020-12-04 23:46 ` Kees Cook
     [not found] ` <CGME20201218075758eucas1p1605768803a5c9edce4fbe54b3e3b859a@eucas1p1.samsung.com>
2020-12-18  7:57   ` Marek Szyprowski
2020-12-18  9:43     ` Masahiro Yamada
2020-12-18 10:05       ` Marek Szyprowski
2020-12-18 15:03         ` Jon Hunter
2020-12-18 15:09           ` Marek Szyprowski
2020-12-18 15:12             ` Jon Hunter
2020-12-18 15:33               ` Jon Hunter
2020-12-18 15:42                 ` Masahiro Yamada
2020-12-18 15:55                   ` Jon Hunter
2020-12-18 16:53                   ` Thierry Reding
2020-12-18 17:54                 ` Linus Torvalds
2020-12-18 20:33                   ` Jon Hunter
2021-01-19 17:48                     ` Thierry Reding
2021-01-19 19:01                       ` Masahiro Yamada

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