Author: John Regehr Date: 2020-02-11T00:05:16-07:00 New Revision: 42ca012befa546d6cddde2155242ca85e155eda4
URL: https://github.com/llvm/llvm-project/commit/42ca012befa546d6cddde2155242ca85e155eda4 DIFF: https://github.com/llvm/llvm-project/commit/42ca012befa546d6cddde2155242ca85e155eda4.diff LOG: remove outdated comparison with other open-source c++ compilers Added: Modified: clang/www/features.html clang/www/index.html clang/www/menu.html.incl Removed: clang/www/comparison.html ################################################################################ diff --git a/clang/www/comparison.html b/clang/www/comparison.html deleted file mode 100755 index 876179c7dec3..000000000000 --- a/clang/www/comparison.html +++ /dev/null @@ -1,190 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" - "http://www.w3.org/TR/html4/strict.dtd";> -<!-- Material used from: HTML 4.01 specs: http://www.w3.org/TR/html401/ --> -<html> -<head> - <META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> - <title>Comparing Clang to other open source compilers</title> - <link type="text/css" rel="stylesheet" href="menu.css"> - <link type="text/css" rel="stylesheet" href="content.css"> -</head> -<body> - <!--#include virtual="menu.html.incl"--> - <div id="content"> - <h1>Clang vs Other Open Source Compilers</h1> - - <p>Building an entirely new compiler front-end is a big task, and it isn't - always clear to people why we decided to do this. Here we compare Clang - and its goals to other open source compiler front-ends that are - available. We restrict the discussion to very specific objective points - to avoid controversy where possible. Also, software is infinitely - mutable, so we don't talk about little details that can be fixed with - a reasonable amount of effort: we'll talk about issues that are - diff icult to fix for architectural or political reasons.</p> - - <p>The goal of this list is to describe how diff erences in goals lead to - diff erent strengths and weaknesses, not to make some compiler look bad. - This will hopefully help you to evaluate whether using Clang is a good - idea for your personal goals. Because we don't know specifically what - <em>you</em> want to do, we describe the features of these compilers in - terms of <em>our</em> goals: if you are only interested in static - analysis, you may not care that something lacks codegen support, for - example.</p> - - <p>Please email <a href="get_involved.html">cfe-dev</a> if you think we should add another compiler to this - list or if you think some characterization is unfair here.</p> - - <ul> - <li><a href="#gcc">Clang vs GCC</a> (GNU Compiler Collection)</li> - <li><a href="#elsa">Clang vs Elsa</a> (Elkhound-based C++ Parser)</li> - <li><a href="#pcc">Clang vs PCC</a> (Portable C Compiler)</li> - </ul> - - - <!--=====================================================================--> - <h2><a name="gcc">Clang vs GCC (GNU Compiler Collection)</a></h2> - <!--=====================================================================--> - - <p>Pro's of GCC vs Clang:</p> - - <ul> - <li>GCC supports languages that Clang does not aim to, such as Java, Ada, - FORTRAN, Go, etc.</li> - <li>GCC supports more targets than LLVM.</li> - <li>GCC supports many language extensions, some of which are not implemented - by Clang. For instance, in C mode, GCC supports - <a href="https://gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html";>nested - functions</a> and has an - <a href="https://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html";>extension - allowing VLAs in structs</a>. - </ul> - - <p>Pro's of Clang vs GCC:</p> - - <ul> - <li>The Clang ASTs and design are intended to be <a - href="features.html#simplecode">easily understandable</a> by - anyone who is familiar with the languages involved and who has a basic - understanding of how a compiler works. GCC has a very old codebase - which presents a steep learning curve to new developers.</li> - <li>Clang is designed as an API from its inception, allowing it to be reused - by source analysis tools, refactoring, IDEs (etc) as well as for code - generation. GCC is built as a monolithic static compiler, which makes - it extremely diff icult to use as an API and integrate into other tools. - Further, its historic design and <a - href="https://gcc.gnu.org/ml/gcc/2007-11/msg00460.html";>current</a> - <a href="https://gcc.gnu.org/ml/gcc/2004-12/msg00888.html";>policy</a> - makes it diff icult to decouple the front-end from the rest of the - compiler. </li> - <li>Various GCC design decisions make it very diff icult to reuse: its build - system is diff icult to modify, you can't link multiple targets into one - binary, you can't link multiple front-ends into one binary, it uses a - custom garbage collector, uses global variables extensively, is not - reentrant or multi-threadable, etc. Clang has none of these problems. - </li> - <li>Clang does not implicitly simplify code as it parses it like GCC does. - Doing so causes many problems for source analysis tools: as one simple - example, if you write "x-x" in your source code, the GCC AST will - contain "0", with no mention of 'x'. This is extremely bad for a - refactoring tool that wants to rename 'x'.</li> - <li>Clang can serialize its AST out to disk and read it back into another - program, which is useful for whole program analysis. GCC does not have - this. GCC's PCH mechanism (which is just a dump of the compiler - memory image) is related, but is architecturally only - able to read the dump back into the exact same executable as the one - that produced it (it is not a structured format).</li> - <li>Clang is <a href="features.html#performance">much faster and uses far - less memory</a> than GCC.</li> - <li>Clang has been designed from the start to provide extremely clear and - concise diagnostics (error and warning messages), and includes support - for <a href="diagnostics.html">expressive diagnostics</a>. - Modern versions of GCC have made significant advances in this area, - incorporating various Clang features such as preserving typedefs in - diagnostics and showing macro expansions, but GCC is still catching - up.</li> - <li>GCC is licensed under the GPL license. <a href="features.html#license"> - Clang uses a BSD license,</a> which allows it to be embedded in - software that is not GPL-licensed.</li> - <li>Clang inherits a number of features from its use of LLVM as a backend, - including support for a bytecode representation for intermediate code, - pluggable optimizers, link-time optimization support, Just-In-Time - compilation, ability to link in multiple code generators, etc.</li> - <li><a href="compatibility.html#cxx">Clang's support for C++</a> is more - compliant than GCC's in many ways.</li> - <li>Clang supports - <a href="https://clang.llvm.org/docs/LanguageExtensions.html";>many language - extensions</a>, some of which are not implemented by GCC. For instance, - Clang provides attributes for checking thread safety and extended vector - types.</li> - </ul> - - <!--=====================================================================--> - <h2><a name="elsa">Clang vs Elsa (Elkhound-based C++ Parser)</a></h2> - <!--=====================================================================--> - - <p>Pro's of Elsa vs Clang:</p> - - <ul> - <li>Elsa's parser and AST is designed to be easily extensible by adding - grammar rules. Clang has a very simple and easily hackable parser, - but requires you to write C++ code to do it.</li> - </ul> - - <p>Pro's of Clang vs Elsa:</p> - - <ul> - <li>Clang's C and C++ support is far more mature and practically useful than - Elsa's, and includes many C++'11 features.</li> - <li>The Elsa community is extremely small and major development work seems - to have ceased in 2005. Work continued to be used by other small - projects (e.g. Oink), but Oink is apparently dead now too. Clang has a - vibrant community including developers that - are paid to work on it full time. In practice this means that you can - file bugs against Clang and they will often be fixed for you. If you - use Elsa, you are (mostly) on your own for bug fixes and feature - enhancements.</li> - <li>Elsa is not built as a stack of reusable libraries like Clang is. It is - very diff icult to use part of Elsa without the whole front-end. For - example, you cannot use Elsa to parse C/ObjC code without building an - AST. You can do this in Clang and it is much faster than building an - AST.</li> - <li>Elsa does not have an integrated preprocessor, which makes it extremely - diff icult to accurately map from a source location in the AST back to - its original position before preprocessing. Like GCC, it does not keep - track of macro expansions.</li> - <li>Elsa is even slower and uses more memory than GCC, which itself requires - far more space and time than Clang.</li> - <li>Elsa only does partial semantic analysis. It is intended to work on - code that is already validated by GCC, so it does not do many semantic - checks required by the languages it implements.</li> - <li>Elsa does not support Objective-C.</li> - <li>Elsa does not support native code generation.</li> - </ul> - - - <!--=====================================================================--> - <h2><a name="pcc">Clang vs PCC (Portable C Compiler)</a></h2> - <!--=====================================================================--> - - <p>Pro's of PCC vs Clang:</p> - - <ul> - <li>The PCC source base is very small and builds quickly with just a C - compiler.</li> - </ul> - - <p>Pro's of Clang vs PCC:</p> - - <ul> - <li>PCC dates from the 1970's and has been dormant for most of that time. - The Clang and LLVM communities are very active.</li> - <li>PCC doesn't support Objective-C or C++ and doesn't aim to support - C++.</li> - <li>PCC's code generation is very limited compared to LLVM. It produces very - inefficient code and does not support many important targets.</li> - <li>Like Elsa, PCC's does not have an integrated preprocessor, making it - extremely diff icult to use it for source analysis tools.</li> - </ul> - </div> -</body> -</html> diff --git a/clang/www/features.html b/clang/www/features.html index 98478193fae8..cd2f9e7b4e2e 100755 --- a/clang/www/features.html +++ b/clang/www/features.html @@ -297,12 +297,12 @@ <h3><a name="real">A real-world, production quality compiler</a></h3> <!--=======================================================================--> <p> -Clang is designed and built by experienced compiler developers who -are increasingly frustrated with the problems that <a -href="comparison.html">existing open source compilers</a> have. Clang is -carefully and thoughtfully designed and built to provide the foundation of a -whole new generation of C/C++/Objective C development tools, and we intend for -it to be production quality.</p> +Clang is designed and built by experienced compiler developers who are +increasingly frustrated with the problems that existing open source +compilers have. Clang is carefully and thoughtfully designed and +built to provide the foundation of a whole new generation of +C/C++/Objective C development tools, and we intend for it to be +production quality.</p> <p>Being a production quality compiler means many things: it means being high performance, being solid and (relatively) bug free, and it means eventually diff --git a/clang/www/index.html b/clang/www/index.html index ce400d6153d3..d568a7b8d414 100755 --- a/clang/www/index.html +++ b/clang/www/index.html @@ -74,9 +74,6 @@ <h2>Why?</h2> motivations for starting work on a new front-end that could meet these needs.</p> - <p>For a more detailed comparison between Clang and other compilers, please - see the <a href="comparison.html">Clang comparison page</a>.</p> - <!--=====================================================================--> <h2>Current Status</h2> <!--=====================================================================--> diff --git a/clang/www/menu.html.incl b/clang/www/menu.html.incl index 9c98f44edd51..657625f5c254 100755 --- a/clang/www/menu.html.incl +++ b/clang/www/menu.html.incl @@ -8,7 +8,6 @@ <a href="http://llvm.org/releases/download.html";>Download</a> <a href="/index.html">About</a> <a href="/features.html">Features</a> - <a href="/comparison.html">Comparisons</a> <a href="/related.html">Related Projects</a> <a href="/docs/UsersManual.html">User's Manual</a> <a href="/compatibility.html">Language Compatibility</a> _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
