[PATCH u-boot v4 06/36] string: make memcpy(), memset(), memcmp() and memmove() visible for LTO

[Simon Glass]

On Thu, 20 May 2021 at 05:25, Marek Behún <marek.behun at nic.cz> wrote:
>
> It seems that sometimes (happening on ARM64, for example with
> turris_mox_defconfig) GCC, when linking with LTO, changes the symbol
> names of some functions, for example lib/string.c's memcpy() function to
> memcpy.isra.0.
>
> This is a problem however when GCC for a code such as this:
>         struct some_struct *info = get_some_struct();
>         struct some struct tmpinfo;
>         tmpinfo = *info;
> emits a call to memcpy() by builtin behaviour, to copy *info to tmpinfo.
>
> This then results in the following linking error:
>   .../lz4.c:93: undefined reference to `memcpy'
>   .../uuid.c:206: more undefined references to `memcpy' follow
>
> GCC's documentation says this about -nodefaultlibs option:
>   The compiler may generate calls to "memcmp", "memset", "memcpy" and
>   "memmove".  These entries are usually resolved by entries in libc.
>   These entry points should be supplied through some other mechanism
>   when this option is specified.
>
> Make these functions visible by using the __used macro to avoid this
> error.
>
> Signed-off-by: Marek Behún <marek.behun at nic.cz>
> ---
>  lib/string.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)

Reviewed-by: Simon Glass <sjg at chromium.org>