[lwip-devel] What is xchar() macro?

[Joel Cunningham]

I'm working on getting IPv6 code building with ARMCC 5 and GCC ARM 
Embedded toolchain.  ARM provides their own standard C library and GCC 
ARM uses newlib.  I'm having problems with ip6_addr.c because neither 
one of these toolchains provide a function/macro called xchar(), but 
both provide the other macros guarded by #ifndef isprint:

#ifndef isprint

#define in_range(c, lo, up) ((u8_t)c >= lo && (u8_t)c <= up)

#define isprint(c) in_range(c, 0x20, 0x7f)

#define isdigit(c) in_range(c, '0', '9')

#define isxdigit(c) (isdigit(c) || in_range(c, 'a', 'f') || in_range(c, 
'A', 'F'))

#define islower(c) in_range(c, 'a', 'z')

#define isspace(c) (c == ' ' || c == '\f' || c == '\n' || c == '\r' || c 
== '\t' || c == '\v')

#define xchar(i) ((char)((i) < 10 ? '0' + (i) : 'A' + (i) - 10))

#endif

Resulting in the following failures:

lwip\src\core\ipv6\ip6_addr.c:255:7: error: implicit declaration of 
function 'xchar' [-Werror=implicit-function-declaration]

    buf[i++] = xchar(((current_block_value & 0xf000) >> 12));

    ^

Looking online, I can't find any information on something called xchar 
that would be part of the standard C library

Joel