curl-curl/docs/INTERNALS.md
Viktor Szakats 0855f30709
kerberos: bump minimum to 1.3 (2003-07-08), drop legacy logic
Previous minimum was: 1.2.4 (2002-02-28)

- assume `gssapi/gssapi.h` header for MIT Kerberos.

  Drop logic detecting this header, and drop alternate logic including
  a bare "gssapi.h". Bare `gssapi.h` is Heimdal-specific. MIT Kerberos
  added support for it for Heimdal compatibility on 2006-11-09,
  redirecting to `gssapi/gssapi.h`. MIT Kerberos supported the latter
  header in the 1990s already.

  Ref: 40e1a016f9 (2008-03-06)
  Ref: d119352001 (2006-11-09)

- configure.ac: stop using `HAVE_GSSAPI_GSSAPI_H`.

  Added in 2010 to support "ancient distros such as RHEL-3" where
  `gssapi/gssapi_krb5.h` did not include `gssapi/gssapi.h`.

  MIT Kerberos includes it since commit:
  d9e959edfa (2003-03-06)
  Released in 1.3 (2003-07-08).

  Bump minimum required version to avoid this issue.

  Reverts cca192e58f (2010-04-16)

Ref: https://web.mit.edu/kerberos/dist/historic.html
Ref: https://sources.debian.org/src/krb5/

Closes #18992
2025-10-10 19:47:08 +02:00

1.7 KiB

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 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 1.3
  • 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.