1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" 2 "http://www.w3.org/TR/html4/strict.dtd"> 3 <html> 4 <head> 5 <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 6 <title>LLVM Developer Policy</title> 7 <link rel="stylesheet" href="llvm.css" type="text/css"> 8 </head> 9 <body> 10 11 <h1>LLVM Developer Policy</h1> 12 <ol> 13 <li><a href="#introduction">Introduction</a></li> 14 <li><a href="#policies">Developer Policies</a> 15 <ol> 16 <li><a href="#informed">Stay Informed</a></li> 17 <li><a href="#patches">Making a Patch</a></li> 18 <li><a href="#reviews">Code Reviews</a></li> 19 <li><a href="#owners">Code Owners</a></li> 20 <li><a href="#testcases">Test Cases</a></li> 21 <li><a href="#quality">Quality</a></li> 22 <li><a href="#commitaccess">Obtaining Commit Access</a></li> 23 <li><a href="#newwork">Making a Major Change</a></li> 24 <li><a href="#incremental">Incremental Development</a></li> 25 <li><a href="#attribution">Attribution of Changes</a></li> 26 </ol></li> 27 <li><a href="#clp">Copyright, License, and Patents</a> 28 <ol> 29 <li><a href="#copyright">Copyright</a></li> 30 <li><a href="#license">License</a></li> 31 <li><a href="#patents">Patents</a></li> 32 </ol></li> 33 </ol> 34 <div class="doc_author">Written by the LLVM Oversight Team</div> 35 36 <!--=========================================================================--> 37 <h2><a name="introduction">Introduction</a></h2> 38 <!--=========================================================================--> 39 <div> 40 <p>This document contains the LLVM Developer Policy which defines the project's 41 policy towards developers and their contributions. The intent of this policy 42 is to eliminate miscommunication, rework, and confusion that might arise from 43 the distributed nature of LLVM's development. By stating the policy in clear 44 terms, we hope each developer can know ahead of time what to expect when 45 making LLVM contributions. This policy covers all llvm.org subprojects, 46 including Clang, LLDB, libc++, etc.</p> 47 <p>This policy is also designed to accomplish the following objectives:</p> 48 49 <ol> 50 <li>Attract both users and developers to the LLVM project.</li> 51 52 <li>Make life as simple and easy for contributors as possible.</li> 53 54 <li>Keep the top of Subversion trees as stable as possible.</li> 55 56 <li>Establish awareness of the project's <a href="#clp">copyright, 57 license, and patent policies</a> with contributors to the project.</li> 58 </ol> 59 60 <p>This policy is aimed at frequent contributors to LLVM. People interested in 61 contributing one-off patches can do so in an informal way by sending them to 62 the 63 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits 64 mailing list</a> and engaging another developer to see it through the 65 process.</p> 66 </div> 67 68 <!--=========================================================================--> 69 <h2><a name="policies">Developer Policies</a></h2> 70 <!--=========================================================================--> 71 <div> 72 <p>This section contains policies that pertain to frequent LLVM developers. We 73 always welcome <a href="#patches">one-off patches</a> from people who do not 74 routinely contribute to LLVM, but we expect more from frequent contributors 75 to keep the system as efficient as possible for everyone. Frequent LLVM 76 contributors are expected to meet the following requirements in order for 77 LLVM to maintain a high standard of quality.<p> 78 79 <!-- _______________________________________________________________________ --> 80 <h3><a name="informed">Stay Informed</a></h3> 81 <div> 82 <p>Developers should stay informed by reading at least the "dev" mailing list 83 for the projects you are interested in, such as 84 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a> for 85 LLVM, <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">cfe-dev</a> 86 for Clang, or <a 87 href="http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev">lldb-dev</a> 88 for LLDB. If you are doing anything more than just casual work on LLVM, it 89 is suggested that you also subscribe to the "commits" mailing list for the 90 subproject you're interested in, such as 91 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>, 92 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits">cfe-commits</a>, 93 or <a href="http://lists.cs.uiuc.edu/mailman/listinfo/lldb-commits">lldb-commits</a>. 94 Reading the "commits" list and paying attention to changes being made by 95 others is a good way to see what other people are interested in and watching 96 the flow of the project as a whole.</p> 97 98 <p>We recommend that active developers register an email account with 99 <a href="http://llvm.org/bugs/">LLVM Bugzilla</a> and preferably subscribe to 100 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs">llvm-bugs</a> 101 email list to keep track of bugs and enhancements occurring in LLVM. We 102 really appreciate people who are proactive at catching incoming bugs in their 103 components and dealing with them promptly.</p> 104 </div> 105 106 <!-- _______________________________________________________________________ --> 107 <h3><a name="patches">Making a Patch</a></h3> 108 109 <div> 110 <p>When making a patch for review, the goal is to make it as easy for the 111 reviewer to read it as possible. As such, we recommend that you:</p> 112 113 <ol> 114 <li>Make your patch against the Subversion trunk, not a branch, and not an old 115 version of LLVM. This makes it easy to apply the patch. For information 116 on how to check out SVN trunk, please see the <a 117 href="GettingStarted.html#checkout">Getting Started Guide</a>.</li> 118 119 <li>Similarly, patches should be submitted soon after they are generated. Old 120 patches may not apply correctly if the underlying code changes between the 121 time the patch was created and the time it is applied.</li> 122 123 <li>Patches should be made with <tt>svn diff</tt>, or similar. If you use 124 a different tool, make sure it uses the <tt>diff -u</tt> format and 125 that it doesn't contain clutter which makes it hard to read.</li> 126 127 <li>If you are modifying generated files, such as the top-level 128 <tt>configure</tt> script, please separate out those changes into 129 a separate patch from the rest of your changes.</li> 130 </ol> 131 132 <p>When sending a patch to a mailing list, it is a good idea to send it as an 133 <em>attachment</em> to the message, not embedded into the text of the 134 message. This ensures that your mailer will not mangle the patch when it 135 sends it (e.g. by making whitespace changes or by wrapping lines).</p> 136 137 <p><em>For Thunderbird users:</em> Before submitting a patch, please open 138 <em>Preferences → Advanced → General → Config Editor</em>, 139 find the key <tt>mail.content_disposition_type</tt>, and set its value to 140 <tt>1</tt>. Without this setting, Thunderbird sends your attachment using 141 <tt>Content-Disposition: inline</tt> rather than <tt>Content-Disposition: 142 attachment</tt>. Apple Mail gamely displays such a file inline, making it 143 difficult to work with for reviewers using that program.</p> 144 </div> 145 146 <!-- _______________________________________________________________________ --> 147 <h3><a name="reviews">Code Reviews</a></h3> 148 <div> 149 <p>LLVM has a code review policy. Code review is one way to increase the quality 150 of software. We generally follow these policies:</p> 151 152 <ol> 153 <li>All developers are required to have significant changes reviewed before 154 they are committed to the repository.</li> 155 156 <li>Code reviews are conducted by email, usually on the llvm-commits 157 list.</li> 158 159 <li>Code can be reviewed either before it is committed or after. We expect 160 major changes to be reviewed before being committed, but smaller changes 161 (or changes where the developer owns the component) can be reviewed after 162 commit.</li> 163 164 <li>The developer responsible for a code change is also responsible for making 165 all necessary review-related changes.</li> 166 167 <li>Code review can be an iterative process, which continues until the patch 168 is ready to be committed.</li> 169 </ol> 170 171 <p>Developers should participate in code reviews as both reviewers and 172 reviewees. If someone is kind enough to review your code, you should return 173 the favor for someone else. Note that anyone is welcome to review and give 174 feedback on a patch, but only people with Subversion write access can approve 175 it.</p> 176 </div> 177 178 <!-- _______________________________________________________________________ --> 179 <h3><a name="owners">Code Owners</a></h3> 180 <div> 181 182 <p>The LLVM Project relies on two features of its process to maintain rapid 183 development in addition to the high quality of its source base: the 184 combination of code review plus post-commit review for trusted maintainers. 185 Having both is a great way for the project to take advantage of the fact that 186 most people do the right thing most of the time, and only commit patches 187 without pre-commit review when they are confident they are right.</p> 188 189 <p>The trick to this is that the project has to guarantee that all patches that 190 are committed are reviewed after they go in: you don't want everyone to 191 assume someone else will review it, allowing the patch to go unreviewed. To 192 solve this problem, we have a notion of an 'owner' for a piece of the code. 193 The sole responsibility of a code owner is to ensure that a commit to their 194 area of the code is appropriately reviewed, either by themself or by someone 195 else. The current code owners are:</p> 196 197 <ol> 198 <li><b>Evan Cheng</b>: Code generator and all targets.</li> 199 200 <li><b>Greg Clayton</b>: LLDB.</li> 201 202 <li><b>Doug Gregor</b>: Clang Frontend Libraries.</li> 203 204 <li><b>Howard Hinnant</b>: libc++.</li> 205 206 <li><b>Anton Korobeynikov</b>: Exception handling, debug information, and 207 Windows codegen.</li> 208 209 <li><b>Ted Kremenek</b>: Clang Static Analyzer.</li> 210 211 <li><b>Chris Lattner</b>: Everything not covered by someone else.</li> 212 213 <li><b>John McCall</b>: Clang LLVM IR generation.</li> 214 215 <li><b>Jakob Olesen</b>: Register allocators and TableGen.</li> 216 217 <li><b>Duncan Sands</b>: dragonegg and llvm-gcc 4.2.</li> 218 219 <li><b>Peter Collingbourne</b>: libclc.</li> 220 221 <li><b>Tobias Grosser</b>: polly.</li> 222 </ol> 223 224 <p>Note that code ownership is completely different than reviewers: anyone can 225 review a piece of code, and we welcome code review from anyone who is 226 interested. Code owners are the "last line of defense" to guarantee that all 227 patches that are committed are actually reviewed.</p> 228 229 <p>Being a code owner is a somewhat unglamorous position, but it is incredibly 230 important for the ongoing success of the project. Because people get busy, 231 interests change, and unexpected things happen, code ownership is purely 232 opt-in, and anyone can choose to resign their "title" at any time. For now, 233 we do not have an official policy on how one gets elected to be a code 234 owner.</p> 235 </div> 236 237 <!-- _______________________________________________________________________ --> 238 <h3><a name="testcases">Test Cases</a></h3> 239 <div> 240 <p>Developers are required to create test cases for any bugs fixed and any new 241 features added. Some tips for getting your testcase approved:</p> 242 243 <ol> 244 <li>All feature and regression test cases are added to the 245 <tt>llvm/test</tt> directory. The appropriate sub-directory should be 246 selected (see the <a href="TestingGuide.html">Testing Guide</a> for 247 details).</li> 248 249 <li>Test cases should be written in <a href="LangRef.html">LLVM assembly 250 language</a> unless the feature or regression being tested requires 251 another language (e.g. the bug being fixed or feature being implemented is 252 in the llvm-gcc C++ front-end, in which case it must be written in 253 C++).</li> 254 255 <li>Test cases, especially for regressions, should be reduced as much as 256 possible, by <a href="Bugpoint.html">bugpoint</a> or manually. It is 257 unacceptable to place an entire failing program into <tt>llvm/test</tt> as 258 this creates a <i>time-to-test</i> burden on all developers. Please keep 259 them short.</li> 260 </ol> 261 262 <p>Note that llvm/test and clang/test are designed for regression and small 263 feature tests only. More extensive test cases (e.g., entire applications, 264 benchmarks, etc) 265 should be added to the <tt>llvm-test</tt> test suite. The llvm-test suite is 266 for coverage (correctness, performance, etc) testing, not feature or 267 regression testing.</p> 268 </div> 269 270 <!-- _______________________________________________________________________ --> 271 <h3><a name="quality">Quality</a></h3> 272 <div> 273 <p>The minimum quality standards that any change must satisfy before being 274 committed to the main development branch are:</p> 275 276 <ol> 277 <li>Code must adhere to the <a href="CodingStandards.html">LLVM Coding 278 Standards</a>.</li> 279 280 <li>Code must compile cleanly (no errors, no warnings) on at least one 281 platform.</li> 282 283 <li>Bug fixes and new features should <a href="#testcases">include a 284 testcase</a> so we know if the fix/feature ever regresses in the 285 future.</li> 286 287 <li>Code must pass the <tt>llvm/test</tt> test suite.</li> 288 289 <li>The code must not cause regressions on a reasonable subset of llvm-test, 290 where "reasonable" depends on the contributor's judgement and the scope of 291 the change (more invasive changes require more testing). A reasonable 292 subset might be something like 293 "<tt>llvm-test/MultiSource/Benchmarks</tt>".</li> 294 </ol> 295 296 <p>Additionally, the committer is responsible for addressing any problems found 297 in the future that the change is responsible for. For example:</p> 298 299 <ul> 300 <li>The code should compile cleanly on all supported platforms.</li> 301 302 <li>The changes should not cause any correctness regressions in the 303 <tt>llvm-test</tt> suite and must not cause any major performance 304 regressions.</li> 305 306 <li>The change set should not cause performance or correctness regressions for 307 the LLVM tools.</li> 308 309 <li>The changes should not cause performance or correctness regressions in 310 code compiled by LLVM on all applicable targets.</li> 311 312 <li>You are expected to address any <a href="http://llvm.org/bugs/">bugzilla 313 bugs</a> that result from your change.</li> 314 </ul> 315 316 <p>We prefer for this to be handled before submission but understand that it 317 isn't possible to test all of this for every submission. Our build bots and 318 nightly testing infrastructure normally finds these problems. A good rule of 319 thumb is to check the nightly testers for regressions the day after your 320 change. Build bots will directly email you if a group of commits that 321 included yours caused a failure. You are expected to check the build bot 322 messages to see if they are your fault and, if so, fix the breakage.</p> 323 324 <p>Commits that violate these quality standards (e.g. are very broken) may be 325 reverted. This is necessary when the change blocks other developers from 326 making progress. The developer is welcome to re-commit the change after the 327 problem has been fixed.</p> 328 </div> 329 330 <!-- _______________________________________________________________________ --> 331 <h3><a name="commitaccess">Obtaining Commit Access</a></h3> 332 <div> 333 334 <p>We grant commit access to contributors with a track record of submitting high 335 quality patches. If you would like commit access, please send an email to 336 <a href="mailto:sabre (a] nondot.org">Chris</a> with the following 337 information:</p> 338 339 <ol> 340 <li>The user name you want to commit with, e.g. "hacker".</li> 341 342 <li>The full name and email address you want message to llvm-commits to come 343 from, e.g. "J. Random Hacker <hacker (a] yoyodyne.com>".</li> 344 345 <li>A "password hash" of the password you want to use, e.g. "2ACR96qjUqsyM". 346 Note that you don't ever tell us what your password is, you just give it 347 to us in an encrypted form. To get this, run "htpasswd" (a utility that 348 comes with apache) in crypt mode (often enabled with "-d"), or find a web 349 page that will do it for you.</li> 350 </ol> 351 352 <p>Once you've been granted commit access, you should be able to check out an 353 LLVM tree with an SVN URL of "https://username@llvm.org/..." instead of the 354 normal anonymous URL of "http://llvm.org/...". The first time you commit 355 you'll have to type in your password. Note that you may get a warning from 356 SVN about an untrusted key, you can ignore this. To verify that your commit 357 access works, please do a test commit (e.g. change a comment or add a blank 358 line). Your first commit to a repository may require the autogenerated email 359 to be approved by a mailing list. This is normal, and will be done when 360 the mailing list owner has time.</p> 361 362 <p>If you have recently been granted commit access, these policies apply:</p> 363 364 <ol> 365 <li>You are granted <i>commit-after-approval</i> to all parts of LLVM. To get 366 approval, submit a <a href="#patches">patch</a> to 367 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits">llvm-commits</a>. 368 When approved you may commit it yourself.</li> 369 370 <li>You are allowed to commit patches without approval which you think are 371 obvious. This is clearly a subjective decision — we simply expect 372 you to use good judgement. Examples include: fixing build breakage, 373 reverting obviously broken patches, documentation/comment changes, any 374 other minor changes.</li> 375 376 <li>You are allowed to commit patches without approval to those portions of 377 LLVM that you have contributed or maintain (i.e., have been assigned 378 responsibility for), with the proviso that such commits must not break the 379 build. This is a "trust but verify" policy and commits of this nature are 380 reviewed after they are committed.</li> 381 382 <li>Multiple violations of these policies or a single egregious violation may 383 cause commit access to be revoked.</li> 384 </ol> 385 386 <p>In any case, your changes are still subject to <a href="#reviews">code 387 review</a> (either before or after they are committed, depending on the 388 nature of the change). You are encouraged to review other peoples' patches 389 as well, but you aren't required to.</p> 390 </div> 391 392 <!-- _______________________________________________________________________ --> 393 <h3><a name="newwork">Making a Major Change</a></h3> 394 <div> 395 <p>When a developer begins a major new project with the aim of contributing it 396 back to LLVM, s/he should inform the community with an email to 397 the <a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">llvmdev</a> 398 email list, to the extent possible. The reason for this is to: 399 400 <ol> 401 <li>keep the community informed about future changes to LLVM, </li> 402 403 <li>avoid duplication of effort by preventing multiple parties working on the 404 same thing and not knowing about it, and</li> 405 406 <li>ensure that any technical issues around the proposed work are discussed 407 and resolved before any significant work is done.</li> 408 </ol> 409 410 <p>The design of LLVM is carefully controlled to ensure that all the pieces fit 411 together well and are as consistent as possible. If you plan to make a major 412 change to the way LLVM works or want to add a major new extension, it is a 413 good idea to get consensus with the development community before you start 414 working on it.</p> 415 416 <p>Once the design of the new feature is finalized, the work itself should be 417 done as a series of <a href="#incremental">incremental changes</a>, not as a 418 long-term development branch.</p> 419 </div> 420 421 <!-- _______________________________________________________________________ --> 422 <h3><a name="incremental">Incremental Development</a></h3> 423 <div> 424 <p>In the LLVM project, we do all significant changes as a series of incremental 425 patches. We have a strong dislike for huge changes or long-term development 426 branches. Long-term development branches have a number of drawbacks:</p> 427 428 <ol> 429 <li>Branches must have mainline merged into them periodically. If the branch 430 development and mainline development occur in the same pieces of code, 431 resolving merge conflicts can take a lot of time.</li> 432 433 <li>Other people in the community tend to ignore work on branches.</li> 434 435 <li>Huge changes (produced when a branch is merged back onto mainline) are 436 extremely difficult to <a href="#reviews">code review</a>.</li> 437 438 <li>Branches are not routinely tested by our nightly tester 439 infrastructure.</li> 440 441 <li>Changes developed as monolithic large changes often don't work until the 442 entire set of changes is done. Breaking it down into a set of smaller 443 changes increases the odds that any of the work will be committed to the 444 main repository.</li> 445 </ol> 446 447 <p>To address these problems, LLVM uses an incremental development style and we 448 require contributors to follow this practice when making a large/invasive 449 change. Some tips:</p> 450 451 <ul> 452 <li>Large/invasive changes usually have a number of secondary changes that are 453 required before the big change can be made (e.g. API cleanup, etc). These 454 sorts of changes can often be done before the major change is done, 455 independently of that work.</li> 456 457 <li>The remaining inter-related work should be decomposed into unrelated sets 458 of changes if possible. Once this is done, define the first increment and 459 get consensus on what the end goal of the change is.</li> 460 461 <li>Each change in the set can be stand alone (e.g. to fix a bug), or part of 462 a planned series of changes that works towards the development goal.</li> 463 464 <li>Each change should be kept as small as possible. This simplifies your work 465 (into a logical progression), simplifies code review and reduces the 466 chance that you will get negative feedback on the change. Small increments 467 also facilitate the maintenance of a high quality code base.</li> 468 469 <li>Often, an independent precursor to a big change is to add a new API and 470 slowly migrate clients to use the new API. Each change to use the new API 471 is often "obvious" and can be committed without review. Once the new API 472 is in place and used, it is much easier to replace the underlying 473 implementation of the API. This implementation change is logically 474 separate from the API change.</li> 475 </ul> 476 477 <p>If you are interested in making a large change, and this scares you, please 478 make sure to first <a href="#newwork">discuss the change/gather consensus</a> 479 then ask about the best way to go about making the change.</p> 480 </div> 481 482 <!-- _______________________________________________________________________ --> 483 <h3><a name="attribution">Attribution of Changes</a></h3> 484 <div> 485 <p>We believe in correct attribution of contributions to their contributors. 486 However, we do not want the source code to be littered with random 487 attributions "this code written by J. Random Hacker" (this is noisy and 488 distracting). In practice, the revision control system keeps a perfect 489 history of who changed what, and the CREDITS.txt file describes higher-level 490 contributions. If you commit a patch for someone else, please say "patch 491 contributed by J. Random Hacker!" in the commit message.</p> 492 493 <p>Overall, please do not add contributor names to the source code.</p> 494 </div> 495 496 </div> 497 498 <!--=========================================================================--> 499 <h2> 500 <a name="clp">Copyright, License, and Patents</a> 501 </h2> 502 <!--=========================================================================--> 503 504 <div> 505 506 <div class="doc_notes"> 507 <p style="text-align:center;font-weight:bold">NOTE: This section deals with 508 legal matters but does not provide legal advice. We are not lawyers — 509 please seek legal counsel from an attorney.</p> 510 </div> 511 512 <div> 513 <p>This section addresses the issues of copyright, license and patents for the 514 LLVM project. The copyright for the code is held by the individual 515 contributors of the code and the terms of its license to LLVM users and 516 developers is the 517 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of 518 Illinois/NCSA Open Source License</a> (with portions dual licensed under the 519 <a href="http://www.opensource.org/licenses/mit-license.php">MIT License</a>, 520 see below). As contributor to the LLVM project, you agree to allow any 521 contributions to the project to licensed under these terms.</p> 522 523 524 <!-- _______________________________________________________________________ --> 525 <h3><a name="copyright">Copyright</a></h3> 526 <div> 527 528 <p>The LLVM project does not require copyright assignments, which means that the 529 copyright for the code in the project is held by its respective contributors 530 who have each agreed to release their contributed code under the terms of the 531 <a href="#license">LLVM License</a>.</p> 532 533 <p>An implication of this is that the LLVM license is unlikely to ever change: 534 changing it would require tracking down all the contributors to LLVM and 535 getting them to agree that a license change is acceptable for their 536 contribution. Since there are no plans to change the license, this is not a 537 cause for concern.</p> 538 539 <p>As a contributor to the project, this means that you (or your company) retain 540 ownership of the code you contribute, that it cannot be used in a way that 541 contradicts the license (which is a liberal BSD-style license), and that the 542 license for your contributions won't change without your approval in the 543 future.</p> 544 545 </div> 546 547 <!-- _______________________________________________________________________ --> 548 <h3><a name="license">License</a></h3> 549 <div> 550 <p>We intend to keep LLVM perpetually open source and to use a liberal open 551 source license. <b>As a contributor to the project, you agree that any 552 contributions be licensed under the terms of the corresponding 553 subproject.</b> 554 All of the code in LLVM is available under the 555 <a href="http://www.opensource.org/licenses/UoI-NCSA.php">University of 556 Illinois/NCSA Open Source License</a>, which boils down to this:</p> 557 558 <ul> 559 <li>You can freely distribute LLVM.</li> 560 <li>You must retain the copyright notice if you redistribute LLVM.</li> 561 <li>Binaries derived from LLVM must reproduce the copyright notice (e.g. in an 562 included readme file).</li> 563 <li>You can't use our names to promote your LLVM derived products.</li> 564 <li>There's no warranty on LLVM at all.</li> 565 </ul> 566 567 <p>We believe this fosters the widest adoption of LLVM because it <b>allows 568 commercial products to be derived from LLVM</b> with few restrictions and 569 without a requirement for making any derived works also open source (i.e. 570 LLVM's license is not a "copyleft" license like the GPL). We suggest that you 571 read the <a href="http://www.opensource.org/licenses/UoI-NCSA.php">License</a> 572 if further clarification is needed.</p> 573 574 <p>In addition to the UIUC license, the runtime library components of LLVM 575 (<b>compiler_rt, libc++, and libclc</b>) are also licensed under the <a 576 href="http://www.opensource.org/licenses/mit-license.php">MIT license</a>, 577 which does not contain the binary redistribution clause. As a user of these 578 runtime libraries, it means that you can choose to use the code under either 579 license (and thus don't need the binary redistribution clause), and as a 580 contributor to the code that you agree that any contributions to these 581 libraries be licensed under both licenses. We feel that this is important 582 for runtime libraries, because they are implicitly linked into applications 583 and therefore should not subject those applications to the binary 584 redistribution clause. This also means that it is ok to move code from (e.g.) 585 libc++ to the LLVM core without concern, but that code cannot be moved from 586 the LLVM core to libc++ without the copyright owner's permission. 587 </p> 588 589 <p>Note that the LLVM Project does distribute llvm-gcc and dragonegg, <b>which 590 are GPL.</b> 591 This means that anything "linked" into llvm-gcc must itself be compatible 592 with the GPL, and must be releasable under the terms of the GPL. This 593 implies that <b>any code linked into llvm-gcc and distributed to others may 594 be subject to the viral aspects of the GPL</b> (for example, a proprietary 595 code generator linked into llvm-gcc must be made available under the GPL). 596 This is not a problem for code already distributed under a more liberal 597 license (like the UIUC license), and GPL-containing subprojects are kept 598 in separate SVN repositories whose LICENSE.txt files specifically indicate 599 that they contain GPL code.</p> 600 601 <p>We have no plans to change the license of LLVM. If you have questions or 602 comments about the license, please contact the 603 <a href="mailto:llvmdev (a] cs.uiuc.edu">LLVM Developer's Mailing List</a>.</p> 604 </div> 605 606 <!-- _______________________________________________________________________ --> 607 <h3><a name="patents">Patents</a></h3> 608 <div> 609 <p>To the best of our knowledge, LLVM does not infringe on any patents (we have 610 actually removed code from LLVM in the past that was found to infringe). 611 Having code in LLVM that infringes on patents would violate an important goal 612 of the project by making it hard or impossible to reuse the code for 613 arbitrary purposes (including commercial use).</p> 614 615 <p>When contributing code, we expect contributors to notify us of any potential 616 for patent-related trouble with their changes (including from third parties). 617 If you or your employer own 618 the rights to a patent and would like to contribute code to LLVM that relies 619 on it, we require that the copyright owner sign an agreement that allows any 620 other user of LLVM to freely use your patent. Please contact 621 the <a href="mailto:llvm-oversight (a] cs.uiuc.edu">oversight group</a> for more 622 details.</p> 623 </div> 624 625 </div> 626 627 </div> 628 629 <!-- *********************************************************************** --> 630 <hr> 631 <address> 632 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img 633 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a> 634 <a href="http://validator.w3.org/check/referer"><img 635 src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a> 636 Written by the 637 <a href="mailto:llvm-oversight (a] cs.uiuc.edu">LLVM Oversight Group</a><br> 638 <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br> 639 Last modified: $Date$ 640 </address> 641 </body> 642 </html> 643
