.\"	$OpenBSD: genassym.sh.8,v 1.9 2015/03/13 19:58:41 jmc Exp $
.\"	$NetBSD: genassym.sh.8,v 1.5 1999/03/17 20:31:19 garbled Exp $
.\"
.\" Copyright (c) 1997 Matthias Pfaller.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\"
.Dd $Mdocdate: March 13 2015 $
.Dt GENASSYM.SH 8
.Os
.Sh NAME
.Nm genassym.sh
.Nd emit an assym.h file
.Sh SYNOPSIS
.Nm sh genassym.sh
.Op Fl c
.Ar C compiler invocation
.Sh DESCRIPTION
.Nm
is a shell script normally used during the kernel build process to
create an assym.h file.
This file defines a number of cpp constants derived from the configuration
information
.Nm
reads from stdin.
The generated file is used by kernel sources
written in assembler to gain access to information (e.g. structure
offsets and sizes) normally only known to the C compiler.
.Pp
.Nm
resides in the
.Pa /sys/kern
directory.
Arguments to
.Nm
are usually of the form
.Ar ${CC} ${CFLAGS} ${CPPFLAGS}
where
.Ar ${CC}
is the C compiler used to compile the kernel, while
.Ar ${CFLAGS}
and
.Ar ${CPPFLAGS}
are flag arguments to the C compiler.
The script creates a C source file from its input.
Then the C compiler is called according to the script's arguments
to compile this file.
.Pp
Normally
.Nm
instructs the C compiler to create an assembler source from the constructed
C source.
The resulting file is then processed to extract the information
needed to create the assym.h file.
The
.Fl c
flag instructs
.Nm
to create slightly different code, generate an executable from this code
and run it.
In both cases the assym.h file is written to stdout.
.Sh DIAGNOSTICS
Either self-explanatory, or generated by one of the programs
called from the script.
The script will exit with the return code from the compiler or, in the
.Fl c
case, with the return code from the generated executable.
.Sh SEE ALSO
.Xr genassym.cf 5
.Sh HISTORY
The
.Nm
script first appeared in
.Ox 2.2 .