Date: Wed, 21 Jan 2009 18:52:45 -0500 From: Alexander Kabaev <kabaev@gmail.com> To: Dimitry Andric <dimitry@andric.com> Cc: freebsd-hackers@freebsd.org, Andrew Brampton <brampton+freebsd-hackers@gmail.com> Subject: Re: Kernel Module - GCC Requires memmove Message-ID: <20090121185245.00739316@kan.dnsalias.net> In-Reply-To: <4977B357.2080500@andric.com> References: <d41814900901210412h4a1aaec6l6945dd79d07d13be@mail.gmail.com> <4977B357.2080500@andric.com>
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On Thu, 22 Jan 2009 00:44:23 +0100
Dimitry Andric <dimitry@andric.com> wrote:
> On 2009-01-21 13:12, Andrew Brampton wrote:
> > The .ii file (post-processed source) did NOT mention memmove at all.
> > So I found it very odd that an undefined symbol existed in the
> > object file. So then I looked in the .s file (asm), and it was
> > clearing making a single call to memmove.
>
> This can (amongst others) occur if you assign structs, e.g.:
>
> int test(void)
> {
> struct foo {
> char bar[100];
> } a, b;
>
> b = a;
> }
>
> Compile this with gcc -O0 -S, and you'll see it generates a call to
> memcpy().
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From GCC's info pages:
Most of the compiler support routines used by GCC are present in
`libgcc', but there are a few exceptions. GCC requires the
freestanding environment provide `memcpy', `memmove', `memset' and
`memcmp'.
</end quote>
We do not provide all necessary functions in kernel and mostly depend
on luck for the kernel to link. Your luck apparently ran out :(
--
Alexander Kabaev
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