musl - Using __BYTE_ORDER without endian.h

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Message-ID: <CACna6rwHSaA9XQWe2dXMSFS6n+NSiLy846S3x97mnUtsdDD24w@mail.gmail.com>
Date: Mon, 22 Jun 2015 08:57:01 +0200
From: Rafał Miłecki <zajec5@...il.com>
To: musl@...ts.openwall.com
Subject: Using __BYTE_ORDER without endian.h

Hi,

So far we were using uClibc in OpenWrt and my following code was working fine:

#include <byteswap.h>
#include <errno.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#if __BYTE_ORDER == __BIG_ENDIAN
#define cpu_to_le32(x) bswap_32(x)
#define le32_to_cpu(x) bswap_32(x)
#elif __BYTE_ORDER == __LITTLE_ENDIAN
#define cpu_to_le32(x) (x)
#define le32_to_cpu(x) (x)
#else
#error "Unsupported endianness"
#endif

Unfortunately is is *silently* broken with musl. When using musl and
not including endian.h directly the condition:
#if __BYTE_ORDER == __BIG_ENDIAN
is always true.

Could you fix this?

I expect either:
1) __BYTE_ORDER to be always available & set correctly
2) Compile error because of __BYTE_ORDER being undefined

I think such silent miscompilation is sth that has to be avoided.

-- 
Rafał

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