[64bit] openldap compilation doesn't produce shared libraries

Kai Tietz ktietz70@googlemail.com
Thu Jun 13 08:38:00 GMT 2013

2013/6/13 Corinna Vinschen wrote:
> On Jun 12 20:52, Yaakov (Cygwin/X) wrote:
>> On 2013-06-10 07:46, Dr. Volker Zell wrote:
>> >I think the stack trace translates to the following:
>> >
>> >Stack trace:
>> >Frame        Function    Args
>> >ber_get_stringbvl
>> >/usr/src/debug/openldap-2.4.35-1/libraries/liblber/decode.c:414
>> >ber_scanf
>> >/usr/src/debug/openldap-2.4.35-1/libraries/liblber/decode.c:790
>> >ldap_get_attribute_ber
>> >/usr/src/debug/openldap-2.4.35-1/libraries/libldap/getattr.c:132
>> >print_entry
>> >/usr/src/debug/openldap-2.4.35-1/clients/tools/ldapsearch.c:1634
>> >main
>> >/usr/src/debug/openldap-2.4.35-1/clients/tools/ldapsearch.c:1222
>> >
>> >The offending code line
>> >     case BvOff:
>> >             res.bo = (char *) b->result + b->off;
>> >             ((struct berval *) (res.bo + tot_size))->bv_val = NULL;   <- line 414
>> >             tot_size = 0;
>> >             break;
>> That is where it is crashing, but after some debugging, AFAICS the
>> real culprit is the call to ber_scanf() in ldap_get_attribute_ber().
>> Presumably because this is a varargs function, the compiler wasn't
>> able to handle the necessary type promotion automatically (ber_len_t
>> is an unsigned long); so b->off was showing here as 0x600000000,
>> taking line 414 off to la-la land.  Patch attached and pushed to
>> Ports git.
> Too bad.  This is a typical problem of projects which have been ported
> to 64 bit, but only to SYSV ABI, not to MS ABI.  The problem never shows
> up in the SYSV ABI (Linux, Solaris, etc), because arguments < 64 bit are
> zero extended when pushed on the stack.  Unfortunately, in the MS ABI,
> parameters < 64 bit are not zero extended so the higher bits can contain
> any random value.  Here, the uncasted 0 is int, so it's pushed on the
> stack with the higher 32 bit set to any garbage this stack address
> contains at the time.
> Given our LP64-ness, I'm wondering if we couldn't tweak gcc to zero
> extend arguments as well, even when otherwise using the MS ABI...
> Corinna
> --
> Corinna Vinschen                  Please, send mails regarding Cygwin to
> Cygwin Maintainer                 cygwin AT cygwin DOT com
> Red Hat

Hmm, well, we could do that, but it means of course in some cases a
performance-penalty.  For preventing some misunderstandings about
MS-ABI I have to note that MS-ABI also extends argument also to
natural-stack-boundary (means 8 byte on x64).  Only difference here is
that no sign-extending is used in general (in oppose to x86_64 ABI).
So as quick feature this isn't implementable AFAICS due it has impact
on behavior and performance.


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