curl/docs/INTERNALS.md
Viktor Szakats 8be9a26451
build: drop Heimdal support, update docs, replace with MIT Kerberos in CI
The kerberos5 library Heimdal is one of three GSS libraries curl support.
It has a memory leak triggered by the new test in #18917 and the project
seems mostly abandoned.

Drop support and steer users to the MIT krb5 or GNU GSS libraries.

Co-authored-by: Daniel Stenberg

Ref: #18928
Closes #18928
Closes #18932
2025-10-09 02:27:29 +02:00

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1.7 KiB
Markdown

<!--
Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
-->
# curl internals
The canonical libcurl internals documentation is now in the [everything
curl](https://everything.curl.dev/internals) 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 1.0.2a
- LibreSSL 2.9.1
- GnuTLS 3.1.10
- mbedTLS 3.2.0
- zlib 1.2.5.2
- libssh2 1.9.0
- c-ares 1.6.0
- libssh 0.9.0
- libidn2 2.0.0
- wolfSSL 3.4.6
- OpenLDAP 2.0
- MIT Kerberos 1.2.4
- nghttp2 1.15.0
## 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.