gawk: Old Extension Mechanism
C.6 Compatibility For Old Extensions
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Dynamic Extensions, describes the supported API and mechanisms
for writing extensions for 'gawk'. This API was introduced in version
4.1. However, for many years 'gawk' provided an extension mechanism
that required knowledge of 'gawk' internals and that was not as well
designed.
In order to provide a transition period, 'gawk' version 4.1 continues
to support the original extension mechanism. This will be true for the
life of exactly one major release. This support will be withdrawn, and
removed from the source code, at the next major release.
Briefly, original-style extensions should be compiled by including
the 'awk.h' header file in the extension source code. Additionally, you
must define the identifier 'GAWK' when building (use '-DGAWK' with
Unix-style compilers). Otherwise, the definitions in 'gawkapi.h' will
cause conflicts with those in 'awk.h' and your extension will not
compile.
Just as in previous versions, you load an old-style extension with
the 'extension()' built-in function (which is not otherwise documented).
This function in turn finds and loads the shared object file containing
the extension and calls its 'dl_load()' C routine.
Because original-style and new-style extensions use different
initialization routines ('dl_load()' versus 'dlload()'), they may safely
be installed in the same directory (to be found by 'AWKLIBPATH') without
conflict.
The 'gawk' development team strongly recommends that you convert any
old extensions that you may have to use the new API described in
Dynamic Extensions.
Info Catalog
gawk: Extension Design
gawk: Notes
gawk: Notes summary