Re: [PATCH] Improve bswap portability

[Schanzenbach, Martin]

Hi,

thanks for noticing.

bswap_* and the builtin __bswap_* are not the same.
The former is a function sometimes provided by the libc, see gnulib [1].
The builtin is provided by compilers (maybe only gcc actually).
I cannot find documentation, but it seems this is sometimes also called 
__builtin_bswap*.

So the patch below does not really address the issue properly and my recent 
patch should not be a relevant regression [2].
I do not know where __bswap_* comes from, but the commit did not really 
introduce that.

I invite you to open a bug report for detailed discussions on android/bionic.
My assumption is that a suitable function needs to be detected in configure.

BR

[1] https://www.gnu.org/software/gnulib/manual/html_node/bswap_005f32.html
[2] 
https://git.gnunet.org/gnunet.git/commit/?id=3ae831780b5681764a7d0505fa94f3fdaa43e1d8

> On 19. Sep 2021, at 10:34, Malte Voos <malte@malvo.org> wrote:
> 
> The official function names are bswap_*, not __bswap_*. The latter won't
> compile with Android's bionic libc.
> ---
> src/include/gnunet_common.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/src/include/gnunet_common.h b/src/include/gnunet_common.h
> index ca3ddceaa..b09fef93f 100644
> --- a/src/include/gnunet_common.h
> +++ b/src/include/gnunet_common.h
> @@ -152,9 +152,9 @@ enum GNUNET_GenericReturnValue
> 
> #if __BYTE_ORDER == __LITTLE_ENDIAN
> #if defined(__linux__)
> -#define BYTE_SWAP_16(x) __bswap_16 (x)
> -#define BYTE_SWAP_32(x) __bswap_32 (x)
> -#define BYTE_SWAP_64(x) __bswap_64 (x)
> +#define BYTE_SWAP_16(x) bswap_16 (x)
> +#define BYTE_SWAP_32(x) bswap_32 (x)
> +#define BYTE_SWAP_64(x) bswap_64 (x)
> #else
> #define BYTE_SWAP_16(x) ((((x) & 0x00ff) << 8) | (((x) & 0xff00) >> 8))
> 
> -- 
> 2.32.0
> 
>