Re: [PATCH] sha1dc: fix for compiling on AIX using IBM XLC compiler
- Date: Wed, 9 May 2018 11:30:08 -0700
- From: Jonathan Nieder <jrnieder@xxxxxxxxx>
- Subject: Re: [PATCH] sha1dc: fix for compiling on AIX using IBM XLC compiler
(+cc: Marc Stevens)
Ævar Arnfjörð Bjarmason wrote:
> On Wed, May 09 2018, jens persson wrote:
>> Hello, first patch. I'm having trouble compiling on AIX using IBMs
>> compiler, leading to
>> unusable binaries. The following patch solved the problem for 2.17.0.
>> The patch below is cut&pasted via gmail to allow for firewalls, but
>> exists in an unmolested form on github:
>> Best regards
Thanks for the patch.
>> Building on AIX using XLC every checkout gives an error:
>> fatal: pack is corrupted (SHA1 mismatch)
>> fatal: index-pack failed
>> Back tracking it was introduced in 2.13.2, most likely in 
>> Add a #ifdef guard based on macros defined at  and .
>> Should perhaps __xlc__ should should be changed to or combined with _AIX
>> based on the behavour of GCC on AIX or XL C on Linux.
>> 1. https://github.com/git/git/commit/6b851e536b05e0c8c61f77b9e4c3e7cedea39ff8
>> 2. https://www.ibm.com/support/knowledgecenter/SSGH2K_13.1.3/com.ibm.xlc1313.aix.doc/compiler_ref/macros_platform.html
>> 3. https://www.ibm.com/support/knowledgecenter/SSGH2K_13.1.3/com.ibm.xlc1313.aix.doc/compiler_ref/xlmacros.html
>> Signed-off-by: jens persson <jens@xxxxxxxxxx>
>> sha1dc/sha1.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> diff --git a/sha1dc/sha1.c b/sha1dc/sha1.c
>> index 25eded139..68a8a0180 100644
>> --- a/sha1dc/sha1.c
>> +++ b/sha1dc/sha1.c
>> @@ -84,7 +84,7 @@
>> /* Not under GCC-alike or glibc or *BSD or newlib */
>> #elif (defined(__ARMEB__) || defined(__THUMBEB__) || defined(__AARCH64EB__) || \
>> defined(__MIPSEB__) || defined(__MIPSEB) || defined(_MIPSEB) || \
>> - defined(__sparc))
>> + defined(__sparc) || (defined(__powerpc) && defined(__xlc__)))
I wonder if there's a simpler way to detect this.
__powerpc seems orthogonal to the goal, since there are little-endian
It appears that XLC defines _BIG_ENDIAN on big-endian machines. I
wonder if we should do
#elif defined(_BYTE_ORDER) && defined(_BIG_ENDIAN) && defined(_LITTLE_ENDIAN)
... as today ...
#elif !defined(_BYTE_ORDER) && defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)
# define SHA1DC_BIGENDIAN
#elif !defined(_BYTE_ORDER) && !defined(_BIG_ENDIAN) && defined(_LITTLE_ENDIAN)
/* little endian. */
It also seems to me that Git should enable the #error in the
fallthrough case. The test suite would catch this kind of problem but
it does not seem that everyone runs the test suite, so a compiler
error is more robust. Is there a #define we can set to enable that?
>> * Should define Big Endian for a whitelist of known processors. See
>> * https://sourceforge.net/p/predef/wiki/Endianness/ and
> This patch looks sane to me, but we don't manage this software but
> instead try to pull it as-is from upstream at
> Which we could apply this, it would be much better if you could submit a
> pull request with this to upstream, and then we can update our copy as I
> did in e.g. 9936c1b52a ("sha1dc: update from upstream", 2017-07-01).