curl/docs/INTERNALS.md

curl internals

The canonical libcurl internals documentation is now in the everything curl book. This file lists supported versions of libs and build tools.

Portability

We write curl and libcurl to compile with C89 compilers on 32-bit and up machines. Most of libcurl assumes more or less POSIX compliance but that is not a requirement.

We write libcurl to build and work with lots of third party tools, and we want it to remain functional and buildable with these and later versions (older versions may still work but is not what we work hard to maintain):

Dependencies

We aim to support these or later versions.

• OpenSSL 0.9.7
• GnuTLS 3.1.10
• zlib 1.1.4
• libssh2 1.0
• c-ares 1.16.0
• libidn2 2.0.0
• wolfSSL 2.0.0
• OpenLDAP 2.0
• MIT Kerberos 1.2.4
• Heimdal ?
• nghttp2 1.15.0
• WinSock 2.2 (on Windows 95+ and Windows CE .NET 4.1+)

Build tools

When writing code (mostly for generating stuff included in release tarballs) we use a few "build tools" and we make sure that we remain functional with these versions:

• GNU Libtool 1.4.2
• GNU Autoconf 2.59
• GNU Automake 1.7
• GNU M4 1.4
• perl 5.8
• roffit 0.5
• cmake 3.7

Library Symbols

All symbols used internally in libcurl must use a Curl_ prefix if they are used in more than a single file. Single-file symbols must be made static. Public ("exported") symbols must use a curl_ prefix. Public API functions are marked with CURL_EXTERN in the public header files so that all others can be hidden on platforms where this is possible.