.\"	$NetBSD: genassym.1,v 1.5 2010/04/13 09:01:10 jruoho Exp $
.\"
.\" Copyright (c) 1997 Matthias Pfaller.
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.Dd April 13, 2010
.Dt GENASSYM 1
.Os
.Sh NAME
.Nm genassym
.Nd emit an assym.h file
.Sh SYNOPSIS
.Nm genassym
.Op Fl c
.Op Fl f
.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
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.
The
.Fl f
flag instructs
.Nm
to create forth code.
.Sh DIAGNOSTICS
Either self-explanatory, or generated by one of the programs
called from the script.
.Sh SEE ALSO
.Xr genassym.cf 5
.Sh HISTORY
The
.Nm
command appeared in
.Nx 1.3
as
.Dq genassym.sh
in
.Pa /usr/src/sys/kern .
It became a userland utility in
.Nx 4.0 .