From 5d5367ed00c22cc194b8a2411b2b4b828751003b Mon Sep 17 00:00:00 2001 From: nsfisis Date: Wed, 31 Aug 2022 23:30:53 +0900 Subject: update hugo --- .../index.html | 48 +++++++++++----------- 1 file changed, 24 insertions(+), 24 deletions(-) (limited to 'docs/posts/2021-10-02/cpp-you-can-use-keywords-in-attributes/index.html') diff --git a/docs/posts/2021-10-02/cpp-you-can-use-keywords-in-attributes/index.html b/docs/posts/2021-10-02/cpp-you-can-use-keywords-in-attributes/index.html index 7261530..38c34aa 100644 --- a/docs/posts/2021-10-02/cpp-you-can-use-keywords-in-attributes/index.html +++ b/docs/posts/2021-10-02/cpp-you-can-use-keywords-in-attributes/index.html @@ -15,7 +15,7 @@ - + @@ -47,26 +47,26 @@ 元 URL: https://qiita.com/nsfisis/items/94090937bcf860cfa93b

タイトル落ち。まずはこのコードを見て欲しい。

-
#include <iostream>
-
-[[alignas]] [[alignof]] [[and]] [[and_eq]] [[asm]] [[auto]] [[bitand]]
-[[bitor]] [[bool]] [[break]] [[case]] [[catch]] [[char]] [[char16_t]]
-[[char32_t]] [[class]] [[compl]] [[const]] [[const_cast]] [[constexpr]]
-[[continue]] [[decltype]] [[default]] [[delete]] [[do]] [[double]]
-[[dynamic_cast]] [[else]] [[enum]] [[explicit]] [[export]] [[extern]] [[false]]
-[[final]] [[float]] [[for]] [[friend]] [[goto]] [[if]] [[inline]] [[int]]
-[[long]] [[mutable]] [[namespace]] [[new]] [[noexcept]] [[not]] [[not_eq]]
-[[nullptr]] [[operator]] [[or]] [[or_eq]] [[override]] [[private]]
-[[protected]] [[public]] [[register]] [[reinterpret_cast]] [[return]] [[short]]
-[[signed]] [[sizeof]] [[static]] [[static_assert]] [[static_cast]] [[struct]]
-[[switch]] [[template]] [[this]] [[thread_local]] [[throw]] [[true]] [[try]]
-[[typedef]] [[typeid]] [[typename]] [[union]] [[unsigned]]
-[[virtual]] [[void]] [[volatile]] [[wchar_t]] [[while]] [[xor]] [[xor_eq]]
-// [[using]]
-int main() {
-    std::cout << "Hello, World!" << std::endl;
-}
-
+
#include <iostream>
+
+[[alignas]] [[alignof]] [[and]] [[and_eq]] [[asm]] [[auto]] [[bitand]]
+[[bitor]] [[bool]] [[break]] [[case]] [[catch]] [[char]] [[char16_t]]
+[[char32_t]] [[class]] [[compl]] [[const]] [[const_cast]] [[constexpr]]
+[[continue]] [[decltype]] [[default]] [[delete]] [[do]] [[double]]
+[[dynamic_cast]] [[else]] [[enum]] [[explicit]] [[export]] [[extern]] [[false]]
+[[final]] [[float]] [[for]] [[friend]] [[goto]] [[if]] [[inline]] [[int]]
+[[long]] [[mutable]] [[namespace]] [[new]] [[noexcept]] [[not]] [[not_eq]]
+[[nullptr]] [[operator]] [[or]] [[or_eq]] [[override]] [[private]]
+[[protected]] [[public]] [[register]] [[reinterpret_cast]] [[return]] [[short]]
+[[signed]] [[sizeof]] [[static]] [[static_assert]] [[static_cast]] [[struct]]
+[[switch]] [[template]] [[this]] [[thread_local]] [[throw]] [[true]] [[try]]
+[[typedef]] [[typeid]] [[typename]] [[union]] [[unsigned]]
+[[virtual]] [[void]] [[volatile]] [[wchar_t]] [[while]] [[xor]] [[xor_eq]]
+// [[using]]
+int main() {
+    std::cout << "Hello, World!" << std::endl;
+}
+

コンパイラのバージョン $ clang++ –version Apple clang version 11.0.0 (clang-1100.0.33.8) @@ -92,9 +92,9 @@ $ clang++ –std=c++17 hoge.cpp

同サイトの [keywords のページ] (https://en.cppreference.com/w/cpp/keyword) から一覧を拝借し、上のコードが出来上がった (C++17 においてキーワードでないものなど、一部省いている)。 大量の警告 (unknown attribute ‘〇〇’ ignored) がコンパイラから出力されるが、コンパイルできる。

上のコードでは [[using]] をコメントアウトしているが、これは using キーワードのみ属性構文の中で意味を持つからであり、このコメントアウトを外すとコンパイルに失敗する。

-
// using の例
-[[using foo: attr1, attr2]] int x; // [[foo::attr1, foo::attr2]] の糖衣構文
-

C++17 の仕様も見てみる (正確には標準化前のドラフト)。

+
// using の例
+[[using foo: attr1, attr2]] int x; // [[foo::attr1, foo::attr2]] の糖衣構文
+

C++17 の仕様も見てみる (正確には標準化前のドラフト)。

引用元: https://timsong-cpp.github.io/cppwp/n4659/dcl.attr#grammar-4

If a keyword or an alternative token that satisfies the syntactic requirements of an identifier is contained in an attribute-token, it is considered an identifier.

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