1# [](https://c-ares.org/) 2 3[](https://cirrus-ci.com/github/c-ares/c-ares) 4[](https://ci.appveyor.com/project/c-ares/c-ares/branch/master) 5[](https://coveralls.io/github/c-ares/c-ares) 6[](https://bestpractices.coreinfrastructure.org/projects/291) 7[](https://bugs.chromium.org/p/oss-fuzz/issues/list?sort=-opened&can=1&q=proj:c-ares) 8[](https://sonarcloud.io/summary/new_code?id=c-ares_c-ares) 9[](https://scan.coverity.com/projects/c-ares) 10 11This is c-ares, an asynchronous resolver library. It is intended for 12applications which need to perform DNS queries without blocking, or need to 13perform multiple DNS queries in parallel. The primary examples of such 14applications are servers which communicate with multiple clients and programs 15with graphical user interfaces. 16 17The full source code is available in the ['c-ares' release archives](https://c-ares.org/download/), 18and in a git repository: https://github.com/c-ares/c-ares. See the 19[INSTALL.md](INSTALL.md) file for build information. 20 21If you find bugs, correct flaws, have questions or have comments in general in 22regard to c-ares (or by all means the original ares too), get in touch with us 23on the c-ares mailing list: https://lists.haxx.se/listinfo/c-ares 24 25c-ares is distributed under the MIT license. 26 27You'll find all c-ares details and news here: 28 https://c-ares.org/ 29 30 31## Notes for c-ares hackers 32 33* The distributed `ares_build.h` file is only intended to be used on systems 34 which can not run the also distributed configure script. 35 36* The distributed `ares_build.h` file is generated as a copy of `ares_build.h.dist` 37 when the c-ares source code distribution archive file is originally created. 38 39* If you check out from git on a non-configure platform, you must run the 40 appropriate `buildconf*` script to set up `ares_build.h` and other local files 41 before being able to compile the library. 42 43* On systems capable of running the `configure` script, the `configure` process 44 will overwrite the distributed `ares_build.h` file with one that is suitable 45 and specific to the library being configured and built, this new file is 46 generated from the `ares_build.h.in` template file. 47 48* If you intend to distribute an already compiled c-ares library you **MUST** 49 also distribute along with it the generated `ares_build.h` which has been 50 used to compile it. Otherwise, the library will be of no use for the users of 51 the library that you have built. It is **your** responsibility to provide this 52 file. No one at the c-ares project can know how you have built the library. 53 54* File `ares_build.h` includes platform and configuration dependent info, 55 and must not be modified by anyone. Configure script generates it for you. 56 57* We cannot assume anything else but very basic compiler features being 58 present. While c-ares requires an ANSI C compiler to build, some of the 59 earlier ANSI compilers clearly can't deal with some preprocessor operators. 60 61* Newlines must remain unix-style for older compilers' sake. 62 63* Comments must be written in the old-style /* unnested C-fashion */ 64 65* Try to keep line lengths below 80 columns. 66
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