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Differential D103987

Start tracking Clang's C implementation status
ClosedPublic

Authored by aaron.ballman on Jun 9 2021, 12:58 PM.

Details

Reviewers
rsmith
erichkeane
jyknight
Summary

We currently have a very useful page tracking our implementation status of C++ features (https://clang.llvm.org/cxx_status.html) but we have nothing similar for C. This patch adds the initial support for tracking this information. It's a work-in-progress.

Currently, the document is generated by hand from the information listed in the latest C2x draft (http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2596.pdf for the moment) on the papers that directly impact the language (as opposed to library features). This means information is missing about all the C versions before C2x and it is missing the papers that have been accepted but not yet rolled into the working draft.

I verified the proposals that I believe Clang definitively does/does not implement, but I marked a number of papers as "unknown" because I've not had the chance to see what support we have for them yet. I expect the "Unknown" columns to dwindle as I get the chance to check their status more thoroughly. I also expect we'll add papers from C17 and potentially C11, but I am not certain I have the bandwidth to go as far back in time as C99 let alone C89. Once the status page for features is done, a future endeavor can add a DR status page.

Assuming that this status page is desirable to others, I figure we can commit the incomplete page and I can add information to it post-commit, as I have the time. One question this work did raise for me is whether we want to update the bug tracker to have specific C versions like we do for C++ (currently, we categorize by standard version for C++ and just use "C" as a catch-all for all the versions of C)?

Diff Detail

Event Timeline

aaron.ballman requested review of this revision.Jun 9 2021, 12:58 PM
aaron.ballman created this revision.
Herald added a project: Restricted Project. · View Herald TranscriptJun 9 2021, 12:58 PM
Harbormaster completed remote builds in B108478: Diff 350982.Jun 9 2021, 1:31 PM
jyknight accepted this revision.Jun 9 2021, 2:54 PM

Sounds like a great plan to me.

I might suggest adding some text about the page being incomplete, so that people don't wonder if the blank sections for pre-C2x are a bug.

This revision is now accepted and ready to land.Jun 9 2021, 2:54 PM
aaron.ballman closed this revision.Jun 10 2021, 9:02 AM
In D103987#2809125, @jyknight wrote:

Sounds like a great plan to me.

I might suggest adding some text about the page being incomplete, so that people don't wonder if the blank sections for pre-C2x are a bug.

Thanks, that's a great suggestion!

I've landed this patch with some additional text about the incompleteness in 3a7a7749417854827cf621eaef6012d31e7a82ab, and I'll update the page as I have the opportunity. If anyone spots anything they think I've misclassified, please let me know.

Revision Contents

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www/
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Diff 350982

clang/www/c_status.html

  • This file was added.
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Clang - C Programming Language Status</title>
<link type="text/css" rel="stylesheet" href="menu.css">
<link type="text/css" rel="stylesheet" href="content.css">
<style type="text/css">
.none { background-color: #FFCCCC }
.partial { background-color: #FFE0B0 }
.unreleased { background-color: #FFFF99 }
.unknown { background-color: #FF55FF }
.full { background-color: #CCFF99 }
.na { background-color: #DDDDDD }
:target { background-color: #FFFFBB; outline: #DDDD55 solid thin; }
th { background-color: #FFDDAA }
td { vertical-align: middle }
tt { white-space: nowrap }
</style>
</head>
<body>
<!--#include virtual="menu.html.incl"-->
<div id="content">
<!--*************************************************************************-->
<h1>C Support in Clang</h1>
<!--*************************************************************************-->
<p>Clang implements the following published and upcoming ISO C standards:</p>
<table width="689" border="1" cellspacing="0">
<tr>
<th>Language Standard</th>
<th>Flag</th>
<th>Available in Clang?</th>
</tr>
<tr>
<td><a href="#c89">C89</a></td>
<td><tt>-std=c89</tt></td>
<td class="full" align="center">Yes</td>
</tr>
<tr>
<td><a href="#c99">C99</a></td>
<td><tt>-std=c99</tt></td>
<td class="full" align="center">Almost certainly</td>
</tr>
<tr>
<td><a href="#c11">C11</a></td>
<td><tt>-std=c11</tt></td>
<td class="full" align="center">Probably</td>
</tr>
<tr>
<td><a href="#c17">C17</a></td>
<td><tt>-std=c17</tt></td>
<td class="full" align="center">Maybe?</td>
</tr>
<tr>
<td><a href="#c2x">C2x</a></td>
<td><tt>-std=c2x</tt></td>
<td class="partial" align="center">Partial</td>
</tr>
</table>
<p>The Clang community is continually striving to improve C standards
compliance between releases. We implement the resolution for defect
reports, but we do not currently track our DR status (help with
tracking DR status is appreciated).</p>
<p>The <a href="https://bugs.llvm.org/">LLVM bug tracker</a> contains a
Clang C component that tracks known bugs with Clang's language
conformance.</p>
<h2 id="c89">C89 implementation status</h2>
<p></p>
<h2 id="c99">C99 implementation status</h2>
<p></p>
<h2 id="c11">C11 implementation status</h2>
<p></p>
<h2 id="c17">C17 implementation status</h2>
<p></p>
<h2 id="c2x">C2x implementation status</h2>
<p></p>
<p>You can use Clang in C2x mode with the <code>-std=c2x</code> option.</p>
<details open>
<summary>List of features and minimum Clang version with support</summary>
<table width="689" border="1" cellspacing="0">
<tr>
<th>Language Feature</th>
<th>C2x Proposal</th>
<th>Available in Clang?</th>
</tr>
<!-- Pre-Oct 2019 Papers -->
<tr>
<td>Evaluation formats</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2186.pdf">N2186</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr>
<td>Clarifying the restrict Keyword v2</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2260.pdf">N2660</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr>
<td>Harmonizing static_assert with C++</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2265.pdf">N2665</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr>
<td>nodiscard attribute</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2667.pdf">N2667</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr>
<td>maybe_unused attribute</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2670.pdf">N2670</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr id="TS18661">
<td rowspan="6">TS 18661 Integration</td>
</tr>
<tr> <!-- Pre-Oct 2019 -->
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2314.pdf">N2314</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr> <!-- Pre-Oct 2019 -->
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2341.pdf">N2341</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr> <!-- Pre-Oct 2019 -->
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2401.pdf">N2401</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr> <!-- Pre-Oct 2019 -->
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2359.pdf">N2359</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr> <!-- Nov 2020 -->
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2546.pdf">N2546</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr>
<td>Preprocessor line numbers unspecified</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2322.htm">N2322</a></td>
<td class="full" align="center">Yes</td>
</tr>
<tr>
<td>deprecated attribute</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2334.pdf">N2334</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr id="Attributes">
<td rowspan="3">Attributes</td>
</tr>
<tr> <!-- Pre-Oct 2019 -->
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2335.pdf">N2335</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr> <!-- Aug 2020 -->
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2554.pdf">N2554</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr>
<td>Defining new types in offsetof</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm">N2350</a></td>
<td class="full" align="center">Yes</td>
</tr>
<tr>
<td>fallthrough attribute</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2408.pdf">N2408</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr>
<td>Two's complement sign representation</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2412.pdf">N2412</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr>
<td>Adding the u8 character prefix</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2418.pdf">N2418</a></td>
<td class="none" align="center">No</td>
</tr>
<tr>
<td>Remove support for function definitions with identifier lists</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2432.pdf">N2432</a></td>
<td class="none" align="center">No</td>
</tr>
<!-- Oct 2019 Papers -->
<tr>
<td>*_IS_IEC_60559 feature test macros</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2379.htm">N2379</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr>
<td>Floating-point negation and conversion</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2416.pdf">N2416</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr>
<td>Annex F.8 update for implementation extensions and rounding</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2384.pdf">N2384</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr>
<td>_Bool definitions for true and false</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2393.pdf">N2393</a></td>
<td class="none" align="center">No</td>
</tr>
<!-- Mar 2020 Papers -->
<tr>
<td>[[nodiscard("should have a reason")]]</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2448.pdf">N2448</a></td>
<td class="full" align="center">Clang 10</td>
</tr>
<tr>
<td>Allowing unnamed parameters in function definitions</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2480.pdf">N2480</a></td>
<td class="full" align="center">Clang 11</td>
</tr>
<!-- Aug 2020 Papers -->
<tr>
<td>Free positioning of labels inside compound statements</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2508.pdf">N2508</a></td>
<td class="none" align="center">No</td>
</tr>
<tr>
<td>Clarification request for C17 example of undefined behavior</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2517.pdf">N2517</a></td>
<td class="none" align="center">No</td>
</tr>
<tr>
<td>Querying attribute support</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2553.pdf">N2553</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<!-- Nov 2020 Papers -->
<tr>
<td>Binary literals</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2549.pdf">N2549</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr>
<td>Allow duplicate attributes</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2557.pdf">N2557</a></td>
<td class="unreleased" align="center">Clang 13</td>
</tr>
<tr>
<td>Character encoding of diagnostic text</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2563.pdf">N2563</a></td>
<td class="full" align="center">Yes</td>
</tr>
<tr>
<td>What we think we reserve</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2572.pdf">N2572</a></td>
<td class="partial" align="center">Yes</td>
</tr>
<tr>
<td>Decimal floating-point triples</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2580.htm">N2580</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr>
<td>Remove mixed wide string literal concatenation</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2594.htm">N2594</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr>
<td>Update to IEC 60559:2020</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2600.pdf">N2600</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
<tr>
<td>Compatibility of Pointers to Arrays with Qualifiers</td>
<td><a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2607.pdf">N2607</a></td>
<td class="unknown" align="center">Unknown</td>
</tr>
</table>
</details>
</div>
</body>
</html>

clang/www/menu.html.incl

Context not available.
<a href="/docs/UsersManual.html">User's Manual</a> <a href="/docs/UsersManual.html">User's Manual</a>
<a href="/compatibility.html">Language&nbsp;Compatibility</a> <a href="/compatibility.html">Language&nbsp;Compatibility</a>
<a href="/docs/LanguageExtensions.html">Language&nbsp;Extensions</a> <a href="/docs/LanguageExtensions.html">Language&nbsp;Extensions</a>
<a href="/c_status.html">C Status</a>
<a href="/cxx_status.html">C++ Status</a> <a href="/cxx_status.html">C++ Status</a>
</div> </div>
Context not available.