1e5dd7070Spatrick<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" 2e5dd7070Spatrick "http://www.w3.org/TR/html4/strict.dtd"> 3e5dd7070Spatrick<html> 4e5dd7070Spatrick<head> 5e5dd7070Spatrick <META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 6e5dd7070Spatrick <title>Clang - Features and Goals</title> 7e5dd7070Spatrick <link type="text/css" rel="stylesheet" href="menu.css"> 8e5dd7070Spatrick <link type="text/css" rel="stylesheet" href="content.css"> 9e5dd7070Spatrick <style type="text/css"> 10e5dd7070Spatrick</style> 11e5dd7070Spatrick</head> 12e5dd7070Spatrick<body> 13e5dd7070Spatrick 14e5dd7070Spatrick<!--#include virtual="menu.html.incl"--> 15e5dd7070Spatrick 16e5dd7070Spatrick<div id="content"> 17e5dd7070Spatrick 18e5dd7070Spatrick<!--*************************************************************************--> 19e5dd7070Spatrick<h1>Clang - Features and Goals</h1> 20e5dd7070Spatrick<!--*************************************************************************--> 21e5dd7070Spatrick 22e5dd7070Spatrick<p> 23e5dd7070SpatrickThis page describes the <a href="index.html#goals">features and goals</a> of 24e5dd7070SpatrickClang in more detail and gives a more broad explanation about what we mean. 25e5dd7070SpatrickThese features are: 26e5dd7070Spatrick</p> 27e5dd7070Spatrick 28e5dd7070Spatrick<p>End-User Features:</p> 29e5dd7070Spatrick 30e5dd7070Spatrick<ul> 31e5dd7070Spatrick<li><a href="#performance">Fast compiles and low memory use</a></li> 32e5dd7070Spatrick<li><a href="#expressivediags">Expressive diagnostics</a></li> 33e5dd7070Spatrick<li><a href="#gcccompat">GCC compatibility</a></li> 34e5dd7070Spatrick</ul> 35e5dd7070Spatrick 36e5dd7070Spatrick<p>Utility and Applications:</p> 37e5dd7070Spatrick 38e5dd7070Spatrick<ul> 39e5dd7070Spatrick<li><a href="#libraryarch">Library based architecture</a></li> 40e5dd7070Spatrick<li><a href="#diverseclients">Support diverse clients</a></li> 41e5dd7070Spatrick<li><a href="#ideintegration">Integration with IDEs</a></li> 42e5dd7070Spatrick<li><a href="#license">Use the LLVM 'BSD' License</a></li> 43e5dd7070Spatrick</ul> 44e5dd7070Spatrick 45e5dd7070Spatrick<p>Internal Design and Implementation:</p> 46e5dd7070Spatrick 47e5dd7070Spatrick<ul> 48e5dd7070Spatrick<li><a href="#real">A real-world, production quality compiler</a></li> 49e5dd7070Spatrick<li><a href="#simplecode">A simple and hackable code base</a></li> 50e5dd7070Spatrick<li><a href="#unifiedparser">A single unified parser for C, Objective C, C++, 51e5dd7070Spatrick and Objective C++</a></li> 52e5dd7070Spatrick<li><a href="#conformance">Conformance with C/C++/ObjC and their 53e5dd7070Spatrick variants</a></li> 54e5dd7070Spatrick</ul> 55e5dd7070Spatrick 56e5dd7070Spatrick<!--*************************************************************************--> 57e5dd7070Spatrick<h2><a name="enduser">End-User Features</a></h2> 58e5dd7070Spatrick<!--*************************************************************************--> 59e5dd7070Spatrick 60e5dd7070Spatrick 61e5dd7070Spatrick<!--=======================================================================--> 62e5dd7070Spatrick<h3><a name="performance">Fast compiles and Low Memory Use</a></h3> 63e5dd7070Spatrick<!--=======================================================================--> 64e5dd7070Spatrick 65e5dd7070Spatrick<p>A major focus of our work on clang is to make it fast, light and scalable. 66e5dd7070SpatrickThe library-based architecture of clang makes it straight-forward to time and 67e5dd7070Spatrickprofile the cost of each layer of the stack, and the driver has a number of 68e5dd7070Spatrickoptions for performance analysis. Many detailed benchmarks can be found online.</p> 69e5dd7070Spatrick 70e5dd7070Spatrick<p>Compile time performance is important, but when using clang as an API, often 71e5dd7070Spatrickmemory use is even more so: the less memory the code takes the more code you can 72e5dd7070Spatrickfit into memory at a time (useful for whole program analysis tools, for 73e5dd7070Spatrickexample).</p> 74e5dd7070Spatrick 75e5dd7070Spatrick<p>In addition to being efficient when pitted head-to-head against GCC in batch 76e5dd7070Spatrickmode, clang is built with a <a href="#libraryarch">library based 77e5dd7070Spatrickarchitecture</a> that makes it relatively easy to adapt it and build new tools 78e5dd7070Spatrickwith it. This means that it is often possible to apply out-of-the-box thinking 79e5dd7070Spatrickand novel techniques to improve compilation in various ways.</p> 80e5dd7070Spatrick 81e5dd7070Spatrick 82e5dd7070Spatrick<!--=======================================================================--> 83e5dd7070Spatrick<h3><a name="expressivediags">Expressive Diagnostics</a></h3> 84e5dd7070Spatrick<!--=======================================================================--> 85e5dd7070Spatrick 86e5dd7070Spatrick<p>In addition to being fast and functional, we aim to make Clang extremely user 87e5dd7070Spatrickfriendly. As far as a command-line compiler goes, this basically boils down to 88e5dd7070Spatrickmaking the diagnostics (error and warning messages) generated by the compiler 89e5dd7070Spatrickbe as useful as possible. There are several ways that we do this, but the 90e5dd7070Spatrickmost important are pinpointing exactly what is wrong in the program, 91e5dd7070Spatrickhighlighting related information so that it is easy to understand at a glance, 92e5dd7070Spatrickand making the wording as clear as possible.</p> 93e5dd7070Spatrick 94e5dd7070Spatrick<p>Here is one simple example that illustrates the quality of Clang diagnostic:</p> 95e5dd7070Spatrick 96e5dd7070Spatrick<pre> 97e5dd7070Spatrick $ <b>clang -fsyntax-only t.c</b> 98e5dd7070Spatrick t.c:7:39: error: invalid operands to binary expression ('int' and 'struct A') 99e5dd7070Spatrick <span style="color:darkgreen"> return y + func(y ? ((SomeA.X + 40) + SomeA) / 42 + SomeA.X : SomeA.X);</span> 100e5dd7070Spatrick <span style="color:blue"> ~~~~~~~~~~~~~~ ^ ~~~~~</span> 101e5dd7070Spatrick</pre> 102e5dd7070Spatrick 103e5dd7070Spatrick<p>Here you can see that you don't even need to see the original source code to 104e5dd7070Spatrickunderstand what is wrong based on the Clang error: Because Clang prints a 105e5dd7070Spatrickcaret, you know exactly <em>which</em> plus it is complaining about. The range 106e5dd7070Spatrickinformation highlights the left and right side of the plus which makes it 107e5dd7070Spatrickimmediately obvious what the compiler is talking about, which is very useful for 108e5dd7070Spatrickcases involving precedence issues and many other situations.</p> 109e5dd7070Spatrick 110e5dd7070Spatrick<p>Clang diagnostics are very polished and have many features. For more 111e5dd7070Spatrickinformation and examples, please see the <a href="diagnostics.html">Expressive 112e5dd7070SpatrickDiagnostics</a> page.</p> 113e5dd7070Spatrick 114e5dd7070Spatrick<!--=======================================================================--> 115e5dd7070Spatrick<h3><a name="gcccompat">GCC Compatibility</a></h3> 116e5dd7070Spatrick<!--=======================================================================--> 117e5dd7070Spatrick 118e5dd7070Spatrick<p>GCC is currently the defacto-standard open source compiler today, and it 119e5dd7070Spatrickroutinely compiles a huge volume of code. GCC supports a huge number of 120e5dd7070Spatrickextensions and features (many of which are undocumented) and a lot of 121e5dd7070Spatrickcode and header files depend on these features in order to build.</p> 122e5dd7070Spatrick 123e5dd7070Spatrick<p>While it would be nice to be able to ignore these extensions and focus on 124e5dd7070Spatrickimplementing the language standards to the letter, pragmatics force us to 125e5dd7070Spatricksupport the GCC extensions that see the most use. Many users just want their 126e5dd7070Spatrickcode to compile, they don't care to argue about whether it is pedantically C99 127e5dd7070Spatrickor not.</p> 128e5dd7070Spatrick 129e5dd7070Spatrick<p>As mentioned above, all 130e5dd7070Spatrickextensions are explicitly recognized as such and marked with extension 131e5dd7070Spatrickdiagnostics, which can be mapped to warnings, errors, or just ignored. 132e5dd7070Spatrick</p> 133e5dd7070Spatrick 134e5dd7070Spatrick 135e5dd7070Spatrick<!--*************************************************************************--> 136e5dd7070Spatrick<h2><a name="applications">Utility and Applications</a></h2> 137e5dd7070Spatrick<!--*************************************************************************--> 138e5dd7070Spatrick 139e5dd7070Spatrick<!--=======================================================================--> 140e5dd7070Spatrick<h3><a name="libraryarch">Library Based Architecture</a></h3> 141e5dd7070Spatrick<!--=======================================================================--> 142e5dd7070Spatrick 143e5dd7070Spatrick<p>A major design concept for clang is its use of a library-based 144e5dd7070Spatrickarchitecture. In this design, various parts of the front-end can be cleanly 145e5dd7070Spatrickdivided into separate libraries which can then be mixed up for different needs 146e5dd7070Spatrickand uses. In addition, the library-based approach encourages good interfaces 147e5dd7070Spatrickand makes it easier for new developers to get involved (because they only need 148e5dd7070Spatrickto understand small pieces of the big picture).</p> 149e5dd7070Spatrick 150e5dd7070Spatrick<blockquote><p> 151e5dd7070Spatrick"The world needs better compiler tools, tools which are built as libraries. 152e5dd7070SpatrickThis design point allows reuse of the tools in new and novel ways. However, 153e5dd7070Spatrickbuilding the tools as libraries isn't enough: they must have clean APIs, be as 154e5dd7070Spatrickdecoupled from each other as possible, and be easy to modify/extend. This 155e5dd7070Spatrickrequires clean layering, decent design, and keeping the libraries independent of 156e5dd7070Spatrickany specific client."</p></blockquote> 157e5dd7070Spatrick 158e5dd7070Spatrick<p> 159e5dd7070SpatrickCurrently, clang is divided into the following libraries and tool: 160e5dd7070Spatrick</p> 161e5dd7070Spatrick 162e5dd7070Spatrick<ul> 163e5dd7070Spatrick<li><b>libsupport</b> - Basic support library, from LLVM.</li> 164e5dd7070Spatrick<li><b>libsystem</b> - System abstraction library, from LLVM.</li> 165e5dd7070Spatrick<li><b>libbasic</b> - Diagnostics, SourceLocations, SourceBuffer abstraction, 166e5dd7070Spatrick file system caching for input source files.</li> 167e5dd7070Spatrick<li><b>libast</b> - Provides classes to represent the C AST, the C type system, 168e5dd7070Spatrick builtin functions, and various helpers for analyzing and manipulating the 169e5dd7070Spatrick AST (visitors, pretty printers, etc).</li> 170e5dd7070Spatrick<li><b>liblex</b> - Lexing and preprocessing, identifier hash table, pragma 171e5dd7070Spatrick handling, tokens, and macro expansion.</li> 172e5dd7070Spatrick<li><b>libparse</b> - Parsing. This library invokes coarse-grained 'Actions' 173e5dd7070Spatrick provided by the client (e.g. libsema builds ASTs) but knows nothing about 174e5dd7070Spatrick ASTs or other client-specific data structures.</li> 175e5dd7070Spatrick<li><b>libsema</b> - Semantic Analysis. This provides a set of parser actions 176e5dd7070Spatrick to build a standardized AST for programs.</li> 177e5dd7070Spatrick<li><b>libcodegen</b> - Lower the AST to LLVM IR for optimization & code 178e5dd7070Spatrick generation.</li> 179e5dd7070Spatrick<li><b>librewrite</b> - Editing of text buffers (important for code rewriting 180e5dd7070Spatrick transformation, like refactoring).</li> 181e5dd7070Spatrick<li><b>libanalysis</b> - Static analysis support.</li> 182e5dd7070Spatrick<li><b>clang</b> - A driver program, client of the libraries at various 183e5dd7070Spatrick levels.</li> 184e5dd7070Spatrick</ul> 185e5dd7070Spatrick 186e5dd7070Spatrick<p>As an example of the power of this library based design.... If you wanted to 187e5dd7070Spatrickbuild a preprocessor, you would take the Basic and Lexer libraries. If you want 188e5dd7070Spatrickan indexer, you would take the previous two and add the Parser library and 189e5dd7070Spatricksome actions for indexing. If you want a refactoring, static analysis, or 190e5dd7070Spatricksource-to-source compiler tool, you would then add the AST building and 191e5dd7070Spatricksemantic analyzer libraries.</p> 192e5dd7070Spatrick 193e5dd7070Spatrick<p>For more information about the low-level implementation details of the 194e5dd7070Spatrickvarious clang libraries, please see the <a href="docs/InternalsManual.html"> 195e5dd7070Spatrickclang Internals Manual</a>.</p> 196e5dd7070Spatrick 197e5dd7070Spatrick<!--=======================================================================--> 198e5dd7070Spatrick<h3><a name="diverseclients">Support Diverse Clients</a></h3> 199e5dd7070Spatrick<!--=======================================================================--> 200e5dd7070Spatrick 201e5dd7070Spatrick<p>Clang is designed and built with many grand plans for how we can use it. The 202e5dd7070Spatrickdriving force is the fact that we use C and C++ daily, and have to suffer due to 203e5dd7070Spatricka lack of good tools available for it. We believe that the C and C++ tools 204e5dd7070Spatrickecosystem has been significantly limited by how difficult it is to parse and 205e5dd7070Spatrickrepresent the source code for these languages, and we aim to rectify this 206e5dd7070Spatrickproblem in clang.</p> 207e5dd7070Spatrick 208e5dd7070Spatrick<p>The problem with this goal is that different clients have very different 209e5dd7070Spatrickrequirements. Consider code generation, for example: a simple front-end that 210e5dd7070Spatrickparses for code generation must analyze the code for validity and emit code 211e5dd7070Spatrickin some intermediate form to pass off to a optimizer or backend. Because 212e5dd7070Spatrickvalidity analysis and code generation can largely be done on the fly, there is 213e5dd7070Spatricknot hard requirement that the front-end actually build up a full AST for all 214e5dd7070Spatrickthe expressions and statements in the code. TCC and GCC are examples of 215e5dd7070Spatrickcompilers that either build no real AST (in the former case) or build a stripped 216e5dd7070Spatrickdown and simplified AST (in the later case) because they focus primarily on 217e5dd7070Spatrickcodegen.</p> 218e5dd7070Spatrick 219e5dd7070Spatrick<p>On the opposite side of the spectrum, some clients (like refactoring) want 220e5dd7070Spatrickhighly detailed information about the original source code and want a complete 221e5dd7070SpatrickAST to describe it with. Refactoring wants to have information about macro 222e5dd7070Spatrickexpansions, the location of every paren expression '(((x)))' vs 'x', full 223e5dd7070Spatrickposition information, and much more. Further, refactoring wants to look 224e5dd7070Spatrick<em>across the whole program</em> to ensure that it is making transformations 225e5dd7070Spatrickthat are safe. Making this efficient and getting this right requires a 226e5dd7070Spatricksignificant amount of engineering and algorithmic work that simply are 227e5dd7070Spatrickunnecessary for a simple static compiler.</p> 228e5dd7070Spatrick 229e5dd7070Spatrick<p>The beauty of the clang approach is that it does not restrict how you use it. 230e5dd7070SpatrickIn particular, it is possible to use the clang preprocessor and parser to build 231e5dd7070Spatrickan extremely quick and light-weight on-the-fly code generator (similar to TCC) 232e5dd7070Spatrickthat does not build an AST at all. As an intermediate step, clang supports 233e5dd7070Spatrickusing the current AST generation and semantic analysis code and having a code 234e5dd7070Spatrickgeneration client free the AST for each function after code generation. Finally, 235e5dd7070Spatrickclang provides support for building and retaining fully-fledged ASTs, and even 236e5dd7070Spatricksupports writing them out to disk.</p> 237e5dd7070Spatrick 238e5dd7070Spatrick<p>Designing the libraries with clean and simple APIs allows these high-level 239e5dd7070Spatrickpolicy decisions to be determined in the client, instead of forcing "one true 240e5dd7070Spatrickway" in the implementation of any of these libraries. Getting this right is 241e5dd7070Spatrickhard, and we don't always get it right the first time, but we fix any problems 242e5dd7070Spatrickwhen we realize we made a mistake.</p> 243e5dd7070Spatrick 244e5dd7070Spatrick<!--=======================================================================--> 245e5dd7070Spatrick<h3 id="ideintegration">Integration with IDEs</h3> 246e5dd7070Spatrick<!--=======================================================================--> 247e5dd7070Spatrick 248e5dd7070Spatrick<p> 249e5dd7070SpatrickWe believe that Integrated Development Environments (IDE's) are a great way 250e5dd7070Spatrickto pull together various pieces of the development puzzle, and aim to make clang 251e5dd7070Spatrickwork well in such an environment. The chief advantage of an IDE is that they 252e5dd7070Spatricktypically have visibility across your entire project and are long-lived 253e5dd7070Spatrickprocesses, whereas stand-alone compiler tools are typically invoked on each 254e5dd7070Spatrickindividual file in the project, and thus have limited scope.</p> 255e5dd7070Spatrick 256e5dd7070Spatrick<p>There are many implications of this difference, but a significant one has to 257e5dd7070Spatrickdo with efficiency and caching: sharing an address space across different files 258e5dd7070Spatrickin a project, means that you can use intelligent caching and other techniques to 259e5dd7070Spatrickdramatically reduce analysis/compilation time.</p> 260e5dd7070Spatrick 261e5dd7070Spatrick<p>A further difference between IDEs and batch compiler is that they often 262e5dd7070Spatrickimpose very different requirements on the front-end: they depend on high 263e5dd7070Spatrickperformance in order to provide a "snappy" experience, and thus really want 264e5dd7070Spatricktechniques like "incremental compilation", "fuzzy parsing", etc. Finally, IDEs 265e5dd7070Spatrickoften have very different requirements than code generation, often requiring 266e5dd7070Spatrickinformation that a codegen-only frontend can throw away. Clang is 267e5dd7070Spatrickspecifically designed and built to capture this information. 268e5dd7070Spatrick</p> 269e5dd7070Spatrick 270e5dd7070Spatrick 271e5dd7070Spatrick<!--=======================================================================--> 272e5dd7070Spatrick<h3><a name="license">Use the LLVM 'Apache 2' License</a></h3> 273e5dd7070Spatrick<!--=======================================================================--> 274e5dd7070Spatrick 275e5dd7070Spatrick<p>We actively intend for clang (and LLVM as a whole) to be used for 276e5dd7070Spatrickcommercial projects, not only as a stand-alone compiler but also as a library 277e5dd7070Spatrickembedded inside a proprietary application. We feel that the license encourages 278e5dd7070Spatrickcontributors to pick up the source and work with it, and believe that those 279e5dd7070Spatrickindividuals and organizations will contribute back their work if they do not 280e5dd7070Spatrickwant to have to maintain a fork forever (which is time consuming and expensive 281e5dd7070Spatrickwhen merges are involved). Further, nobody makes money on compilers these days, 282e5dd7070Spatrickbut many people need them to get bigger goals accomplished: it makes sense for 283e5dd7070Spatrickeveryone to work together.</p> 284e5dd7070Spatrick 285e5dd7070Spatrick<p>For more information about the LLVM/clang license, please see the <a 286e5dd7070Spatrickhref="https://llvm.org/docs/DeveloperPolicy.html#copyright-license-and-patents">LLVM License 287e5dd7070SpatrickDescription</a> for more information.</p> 288e5dd7070Spatrick 289e5dd7070Spatrick 290e5dd7070Spatrick 291e5dd7070Spatrick<!--*************************************************************************--> 292e5dd7070Spatrick<h2><a name="design">Internal Design and Implementation</a></h2> 293e5dd7070Spatrick<!--*************************************************************************--> 294e5dd7070Spatrick 295e5dd7070Spatrick<!--=======================================================================--> 296e5dd7070Spatrick<h3><a name="real">A real-world, production quality compiler</a></h3> 297e5dd7070Spatrick<!--=======================================================================--> 298e5dd7070Spatrick 299e5dd7070Spatrick<p> 300*ec727ea7SpatrickClang is designed and built by experienced compiler developers who are 301*ec727ea7Spatrickincreasingly frustrated with the problems that existing open source 302*ec727ea7Spatrickcompilers have. Clang is carefully and thoughtfully designed and 303*ec727ea7Spatrickbuilt to provide the foundation of a whole new generation of 304*ec727ea7SpatrickC/C++/Objective C development tools, and we intend for it to be 305*ec727ea7Spatrickproduction quality.</p> 306e5dd7070Spatrick 307e5dd7070Spatrick<p>Being a production quality compiler means many things: it means being high 308e5dd7070Spatrickperformance, being solid and (relatively) bug free, and it means eventually 309e5dd7070Spatrickbeing used and depended on by a broad range of people. While we are still in 310e5dd7070Spatrickthe early development stages, we strongly believe that this will become a 311e5dd7070Spatrickreality.</p> 312e5dd7070Spatrick 313e5dd7070Spatrick<!--=======================================================================--> 314e5dd7070Spatrick<h3><a name="simplecode">A simple and hackable code base</a></h3> 315e5dd7070Spatrick<!--=======================================================================--> 316e5dd7070Spatrick 317e5dd7070Spatrick<p>Our goal is to make it possible for anyone with a basic understanding 318e5dd7070Spatrickof compilers and working knowledge of the C/C++/ObjC languages to understand and 319e5dd7070Spatrickextend the clang source base. A large part of this falls out of our decision to 320e5dd7070Spatrickmake the AST mirror the languages as closely as possible: you have your friendly 321e5dd7070Spatrickif statement, for statement, parenthesis expression, structs, unions, etc, all 322e5dd7070Spatrickrepresented in a simple and explicit way.</p> 323e5dd7070Spatrick 324e5dd7070Spatrick<p>In addition to a simple design, we work to make the source base approachable 325e5dd7070Spatrickby commenting it well, including citations of the language standards where 326e5dd7070Spatrickappropriate, and designing the code for simplicity. Beyond that, clang offers 327e5dd7070Spatricka set of AST dumpers, printers, and visualizers that make it easy to put code in 328e5dd7070Spatrickand see how it is represented.</p> 329e5dd7070Spatrick 330e5dd7070Spatrick<!--=======================================================================--> 331e5dd7070Spatrick<h3><a name="unifiedparser">A single unified parser for C, Objective C, C++, 332e5dd7070Spatrickand Objective C++</a></h3> 333e5dd7070Spatrick<!--=======================================================================--> 334e5dd7070Spatrick 335e5dd7070Spatrick<p>Clang is the "C Language Family Front-end", which means we intend to support 336e5dd7070Spatrickthe most popular members of the C family. We are convinced that the right 337e5dd7070Spatrickparsing technology for this class of languages is a hand-built recursive-descent 338e5dd7070Spatrickparser. Because it is plain C++ code, recursive descent makes it very easy for 339e5dd7070Spatricknew developers to understand the code, it easily supports ad-hoc rules and other 340e5dd7070Spatrickstrange hacks required by C/C++, and makes it straight-forward to implement 341e5dd7070Spatrickexcellent diagnostics and error recovery.</p> 342e5dd7070Spatrick 343e5dd7070Spatrick<p>We believe that implementing C/C++/ObjC in a single unified parser makes the 344e5dd7070Spatrickend result easier to maintain and evolve than maintaining a separate C and C++ 345e5dd7070Spatrickparser which must be bugfixed and maintained independently of each other.</p> 346e5dd7070Spatrick 347e5dd7070Spatrick<!--=======================================================================--> 348e5dd7070Spatrick<h3><a name="conformance">Conformance with C/C++/ObjC and their 349e5dd7070Spatrick variants</a></h3> 350e5dd7070Spatrick<!--=======================================================================--> 351e5dd7070Spatrick 352e5dd7070Spatrick<p>When you start work on implementing a language, you find out that there is a 353e5dd7070Spatrickhuge gap between how the language works and how most people understand it to 354e5dd7070Spatrickwork. This gap is the difference between a normal programmer and a (scary? 355e5dd7070Spatricksuper-natural?) "language lawyer", who knows the ins and outs of the language 356e5dd7070Spatrickand can grok standardese with ease.</p> 357e5dd7070Spatrick 358e5dd7070Spatrick<p>In practice, being conformant with the languages means that we aim to support 359e5dd7070Spatrickthe full language, including the dark and dusty corners (like trigraphs, 360e5dd7070Spatrickpreprocessor arcana, C99 VLAs, etc). Where we support extensions above and 361e5dd7070Spatrickbeyond what the standard officially allows, we make an effort to explicitly call 362e5dd7070Spatrickthis out in the code and emit warnings about it (which are disabled by default, 363e5dd7070Spatrickbut can optionally be mapped to either warnings or errors), allowing you to use 364e5dd7070Spatrickclang in "strict" mode if you desire.</p> 365e5dd7070Spatrick 366e5dd7070Spatrick</div> 367e5dd7070Spatrick</body> 368e5dd7070Spatrick</html> 369