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| author | Craig Jennings <c@cjennings.net> | 2025-08-14 22:58:58 -0500 |
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| committer | Craig Jennings <c@cjennings.net> | 2025-08-14 22:58:58 -0500 |
| commit | 82ba818ff456bcd6d56a06226e3f27e98fbb55c3 (patch) | |
| tree | 158cfc17b2f644a10f063cb546752cfaae12c97f /devdocs/c/language%2Fattributes%2Fnodiscard.html | |
| parent | 9278ddd4ea1a8b1a4c1edaa8894516e3f48d245b (diff) | |
| download | dotemacs-82ba818ff456bcd6d56a06226e3f27e98fbb55c3.tar.gz dotemacs-82ba818ff456bcd6d56a06226e3f27e98fbb55c3.zip | |
removing all downloaded devdocs files
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| -rw-r--r-- | devdocs/c/language%2Fattributes%2Fnodiscard.html | 42 |
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diff --git a/devdocs/c/language%2Fattributes%2Fnodiscard.html b/devdocs/c/language%2Fattributes%2Fnodiscard.html deleted file mode 100644 index 35c94f7d..00000000 --- a/devdocs/c/language%2Fattributes%2Fnodiscard.html +++ /dev/null @@ -1,42 +0,0 @@ - <h1 id="firstHeading" class="firstHeading">C attribute: nodiscard <span class="t-mark-rev t-since-c23">(since C23)</span> -</h1> <p>If a function declared <code>nodiscard</code> or a function returning a struct/union/enum declared <code>nodiscard</code> by value is called from a <a href="../expressions" title="c/language/expressions">discarded-value expression</a> other than a cast to <code>void</code>, the compiler is encouraged to issue a warning.</p> -<h3 id="Syntax"> Syntax</h3> <table class="t-sdsc-begin"> <tr class="t-sdsc"> <td> <code>[[</code> <code>nodiscard</code> <code>]]</code><br><code>[[</code> <code>__nodiscard__</code> <code>]]</code> </td> <td> (1) </td> <td class="t-sdsc-nopad"> </td> -</tr> <tr class="t-sdsc"> <td> <code>[[</code> <code>nodiscard</code> <code>(</code> <span class="t-spar">string-literal</span> <code>)</code> <code>]]</code><br><code>[[</code> <code>__nodiscard__</code> <code>(</code> <span class="t-spar">string-literal</span> <code>)</code> <code>]]</code> </td> <td> (2) </td> <td class="t-sdsc-nopad"> </td> -</tr> -</table> <table class="t-par-begin"> <tr class="t-par"> <td> <span class="t-spar">string-literal</span> </td> <td> - </td> <td> text that could be used to explain the rationale for why the result should not be discarded </td> -</tr> -</table> <h3 id="Explanation"> Explanation</h3> <p>Appears in a function declaration, enumeration declaration, or struct/union declaration.</p> -<p>If, from a <a href="../expressions" title="c/language/expressions">discarded-value expression</a> other than a cast to <code>void</code>,</p> -<ul> -<li> a function declared <code>nodiscard</code> is called, or </li> -<li> a function returning a struct/union/enum declared <code>nodiscard</code> is called, </li> -</ul> <p>the compiler is encouraged to issue a warning.</p> -<p>The <span class="t-spar">string-literal</span>, if specified, is usually included in the warnings.</p> -<h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">struct [[nodiscard]] error_info { int status; /*...*/ }; -struct error_info enable_missile_safety_mode() { /*...*/ return (struct error_info){0}; } -void launch_missiles() { /*...*/ } -void test_missiles() { - enable_missile_safety_mode(); // compiler may warn on discarding a nodiscard value - launch_missiles(); -} -struct error_info* foo() { static struct error_info e; /*...*/ return &e; } -void f1() { - foo(); // nodiscard type itself is not returned, no warning -} -// nodiscard( string-literal ): -[[nodiscard("PURE FUN")]] int strategic_value(int x, int y) { return x ^ y; } - -int main() -{ - strategic_value(4,2); // compiler may warn on discarding a nodiscard value - int z = strategic_value(0,0); // OK: return value is not discarded - return z; -}</pre></div> <p>Possible output:</p> -<div class="text source-text"><pre data-language="c">game.cpp:5:4: warning: ignoring return value of function declared with 'nodiscard' attribute -game.cpp:17:5: warning: ignoring return value of function declared with 'nodiscard' attribute: PURE FUN</pre></div> </div> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/language/attributes/nodiscard" title="cpp/language/attributes/nodiscard">C++ documentation</a></span> for <code>nodiscard</code> </td> -</tr> </table> <div class="_attribution"> - <p class="_attribution-p"> - © cppreference.com<br>Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.<br> - <a href="https://en.cppreference.com/w/c/language/attributes/nodiscard" class="_attribution-link">https://en.cppreference.com/w/c/language/attributes/nodiscard</a> - </p> -</div> |
