We have a long history of INVALID bugs about std functions being available in the global namespace (PRs 27846, 67566, 82619, 99865, 110602, 111553, probably others). Let's document it.
Also de-prioritize the C++98-only bugs, which are unlikely to affect anybody nowadays. OK for wwwdocs? -- >8 -- Add ADL to C++ non-bugs Also move the item about C++98 'export' to the end, and update the item about <: digraphs that only applies to C++98. --- htdocs/bugs/index.html | 36 ++++++++++++++++++++++++------------ 1 file changed, 24 insertions(+), 12 deletions(-) diff --git a/htdocs/bugs/index.html b/htdocs/bugs/index.html index 813b78c0..41edc561 100644 --- a/htdocs/bugs/index.html +++ b/htdocs/bugs/index.html @@ -539,15 +539,15 @@ for details. <h2 id="nonbugs_cxx">C++</h2> <dl> -<dt><code>export</code></dt> -<dd><p>Most C++ compilers (G++ included) never implemented C++98 -<code>export</code>, which was removed in C++11, and the keyword reused in -C++20 by the Modules feature. The C++98 feature was intended to support -separate compilation of template declarations and -definitions. Without <code>export</code>, a template definition must be in -scope to be used. The obvious workaround is simply to place all definitions in -the header itself. Alternatively, the compilation unit containing template -definitions may be included from the header.</p></dd> +<dt>Functions can be called without qualifying them with their namespace.</dt> +<dd> +Argument Dependent Lookup (ADL) means that functions can be found in namespaces +associated with their arguments. This means that <code>move(arg)</code> can +call <code>std::move</code> if <code>arg</code> is a type defined in namespace +<code>std</code>, such as <code>std::string</code> or <code>std::vector</code>. +If <code>std::move</code> is not the function you intended to call, use a +qualified name such as <code>::move(arg)</code> or <code>foo::move(arg)</code>. +</dd> <dt>Nested classes can access private members and types of the containing class.</dt> @@ -597,9 +597,9 @@ handler and catch it in the main thread.</p></dd> <dd><p>If you have a class in the global namespace, say named <code>X</code>, and want to give it as a template argument to some other class, say <code>std::vector</code>, then <code>std::vector<::X></code> -fails with a parser error.</p> +fails with a parser error in C++98/C++03 mode.</p> -<p>The reason is that the standard mandates that the sequence +<p>The reason is that the C++98 standard mandates that the sequence <code><:</code> is treated as if it were the token <code>[</code>. (There are several such combinations of characters - they are called <em>digraphs</em>.) Depending on the version, the compiler then reports @@ -608,7 +608,19 @@ a parse error before the character <code>:</code> (the colon before <p>The simplest way to avoid this is to write <code>std::vector< ::X></code>, i.e. place a space between the opening angle bracket -and the scope operator.</p></dd> +and the scope operator, or compile using C++11 or later. Defect report 1104 +changed the parser rules so that <code><::</code> works as expected. +</p></dd> + +<dt><code>export</code></dt> +<dd><p>Most C++ compilers (G++ included) never implemented C++98 +<code>export</code>, which was removed in C++11, and the keyword reused in +C++20 by the Modules feature. The C++98 feature was intended to support +separate compilation of template declarations and +definitions. Without <code>export</code>, a template definition must be in +scope to be used. The obvious workaround is simply to place all definitions in +the header itself. Alternatively, the compilation unit containing template +definitions may be included from the header.</p></dd> </dl> <h3 id="upgrading">Common problems when upgrading the compiler</h3> -- 2.41.0