1# curl internals 2 3The canonical libcurl internals documentation is now in the [everything 4curl](https://everything.curl.dev/internals) book. This file lists supported 5versions of libs and build tools. 6 7## Portability 8 9 We write curl and libcurl to compile with C89 compilers on 32-bit and up 10 machines. Most of libcurl assumes more or less POSIX compliance but that is 11 not a requirement. 12 13 We write libcurl to build and work with lots of third party tools, and we 14 want it to remain functional and buildable with these and later versions 15 (older versions may still work but is not what we work hard to maintain): 16 17## Dependencies 18 19 We aim to support these or later versions. 20 21 - OpenSSL 0.9.7 22 - GnuTLS 3.1.10 23 - zlib 1.1.4 24 - libssh2 1.0 25 - c-ares 1.16.0 26 - libidn2 2.0.0 27 - wolfSSL 2.0.0 28 - OpenLDAP 2.0 29 - MIT Kerberos 1.2.4 30 - Heimdal ? 31 - nghttp2 1.15.0 32 - WinSock 2.2 (on Windows 95+ and Windows CE .NET 4.1+) 33 34## Build tools 35 36 When writing code (mostly for generating stuff included in release tarballs) 37 we use a few "build tools" and we make sure that we remain functional with 38 these versions: 39 40 - GNU Libtool 1.4.2 41 - GNU Autoconf 2.59 42 - GNU Automake 1.7 43 - GNU M4 1.4 44 - perl 5.6 45 - roffit 0.5 46 - nroff any version that supports `-man [in] [out]` 47 - cmake 3.7 48 49Library Symbols 50=============== 51 52 All symbols used internally in libcurl must use a `Curl_` prefix if they are 53 used in more than a single file. Single-file symbols must be made static. 54 Public ("exported") symbols must use a `curl_` prefix. Public API functions 55 are marked with `CURL_EXTERN` in the public header files so that all others 56 can be hidden on platforms where this is possible. 57