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Date: Thu, 2 May 1996 15:50:29 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199605020550.PAA30427@godzilla.zeta.org.au>
To: terry@lambert.org
Subject: Re: execve
Cc: chuckr@Glue.umd.edu, freebsd-current@freebsd.org,
        joerg_wunsch@uriah.heep.sax.de
Sender: owner-current@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

>The big magic is that we don't have to have another object file
>that does:

>#ifdef AOUT
>static const struct execsw aout_execsw = { exec_aout_imgact, "a.out" };
>#endif
>#ifdef ELF
>static const struct execsw elf_execsw = { exec_elf_imgact, "ELF" };
>#endif
>const struct linker_set execsw_set = {
>#ifdef AOUT
>#ifdef ELF
>	2,
>#else
>	1,
>#endif
>#else
>#ifdef ELF
>	1,
>#else
>	0,
>#endif
>#endif
>	{
>#ifdef AOUT
>		{ (caddr_t)&aout_execsw },
>#endif
>#ifdef ELF
>		{ (caddr_t)&elf_execsw },
>#endif
>		NULL
>	}
>};

>To make ELF and AOUT optional (plus #ifdef IBCS2, #ifdef SHELL,
>#ifdef GZIP ...).

OTOH, it would be easy to change config to emit:

static const struct execsw aout_execsw = { exec_aout_imgact, "a.out" };
static const struct execsw elf_execsw = { exec_elf_imgact, "ELF" };
const struct linker_set execsw_set = {
	2,
	{
		{ (caddr_t)&aout_execsw },
		{ (caddr_t)&elf_execsw },
		NULL
	}
};

Bruce