[PATCH] PR lto/94249: Correct endianness detection with the __BYTE_ORDER macro

[Martin Liška]

On 4/1/20 7:01 AM, Hans-Peter Nilsson wrote:
> On Tue, 31 Mar 2020, Maciej W. Rozycki wrote:
>> Correct an issue with GCC commit 906b3eb9df6c ("Improve endianess
>> detection.") and fix a typo in the __BYTE_ORDER fallback macro check
>> that causes compilation errors like:
>>
>> .../include/plugin-api.h:162:2: error: #error "Could not detect architecture endianess"
>>
>> on systems that do not provide the __BYTE_ORDER__ macro.
> 
>> Index: binutils/include/plugin-api.h
>> ===================================================================
>> --- binutils.orig/include/plugin-api.h
>> +++ binutils/include/plugin-api.h
>> @@ -51,7 +51,7 @@
>>   /* Older GCC releases (<4.6.0) can make detection from glibc macros.  */
>>   #if defined(__GLIBC__) || defined(__GNU_LIBRARY__) || defined(__ANDROID__)
>>   #include <endian.h>
>> -#ifdef _BYTE_ORDER
>> +#ifdef __BYTE_ORDER
>>   #if __BYTE_ORDER == __LITTLE_ENDIAN
>>   #define PLUGIN_LITTLE_ENDIAN 1
>>   #elif __BYTE_ORDER == __BIG_ENDIAN
> 
> FWIW, I was about to commit that as obvious, also the bignum.h
> inclusion thing!
> 
> The only question being, how the typo passed any kind of testing
> in the first place...

Because I don't have a legacy system with an ancient glibc version.
Note that testing matrix for such a change is massive, including such
exotic targets like SUN, minix, Windows, ...

>  No actually, there's also the question
> why the plugin-API needs to bother with host endianness.  It's
> not like endians are going to be different between plugins and
> gcc on host.

No, the plugin endianess matches with a host compiler endianess.
Martin

> 
> brgds, H-P
>