The binding generator is part of the gcc compiler and can be
invoked via the -fdump-ada-spec switch, which will generate Ada
spec files for the header files specified on the command line, and all
header files needed by these files transitively. For example:
$ gcc -c -fdump-ada-spec -C /usr/include/time.h $ gcc -c *.ads
will generate, under GNU/Linux, the following files: time_h.ads,
bits_time_h.ads, stddef_h.ads, bits_types_h.ads which
correspond to the files /usr/include/time.h,
/usr/include/bits/time.h, etc…, and then compile these Ada specs.
That is to say, the name of the Ada specs is in keeping with the relative path
under /usr/include/ of the header files. This behavior is specific to
paths ending with /include/; in all the other cases, the name of the
Ada specs is derived from the simple name of the header files instead.
The -C switch tells gcc to extract comments from headers,
and will attempt to generate corresponding Ada comments.
If you want to generate a single Ada file and not the transitive closure, you
can use instead the -fdump-ada-spec-slim switch.
You can optionally specify a parent unit, of which all generated units will
be children, using -fada-spec-parent=`unit'.
The simple gcc`-based command works only for C headers. For C++ headers
you need to use either the g++ command or the combination gcc -x c++`.
In some cases, the generated bindings will be more complete or more meaningful
when defining some macros, which you can do via the -D switch. This
is for example the case with Xlib.h under GNU/Linux:
$ gcc -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
The above will generate more complete bindings than a straight call without
the -DXLIB_ILLEGAL_ACCESS switch.
In other cases, it is not possible to parse a header file in a stand-alone
manner, because other include files need to be included first. In this
case, the solution is to create a small header file including the needed
#include and possible #define directives. For example, to
generate Ada bindings for readline/readline.h, you need to first
include stdio.h, so you can create a file with the following two
lines in e.g. readline1.h:
#include <stdio.h> #include <readline/readline.h>
and then generate Ada bindings from this file:
$ gcc -c -fdump-ada-spec readline1.h