Re: Cygwin linking rules

On 09/29/2018 12:09 PM, Andrew Dunstan wrote:
>
>
> On 09/29/2018 11:35 AM, Tom Lane wrote:
>> Most of the buildfarm is now happy with the changes I made to have
>> libpq + ecpg get src/port and src/common files via libraries ...
>> but lorikeet isn't.  It gets through the core regression tests fine
>> (so libpq, per se, works), but contrib/dblink fails:
>>
>> ! ERROR:  could not establish connection
>> ! DETAIL:  libpq is incorrectly linked to backend functions
>>
>> What this means is that libpq is calling the backend version of
>> src/common/link-canary.c rather than the frontend version.
>> Why would it do the right thing normally and the wrong thing in dblink?
>>
>> I can think of a few theories but I lack the ability to investigate:
>>
>> 1. Maybe the dblink.dll build is pulling in libpq.a rather than
>> establishing a reference to libpq.dll.  If so, the wrong things would
>> happen because libpq.a won't contain the src/common/ files that
>> libpq needs.  (It seems like libpq.a is an active hazard given
>> this.  Why are we building it at all?)
>>
>> 2. Maybe we need a --version-script option or something equivalent
>> to get libpq.dll's references to be preferentially resolved internally
>> rather than to the backend.  But this doesn't really explain why it
>> worked properly before.
>>
>>
>
>
>
> I will see if I can determine if 1) is the cause. I don't know enough, 
> or in fact anything, about 2), so don;t know that I can help there 
> without advice.
>
>



It certainly looks like it's not linked to libpq.dll:

    Microsoft (R) COFF/PE Dumper Version 14.15.26726.0
    Copyright (C) Microsoft Corporation.  All rights reserved.


    Dump of file
    \cygwin64\home\andrew\\bf64\root\HEAD\inst\lib\postgresql\dblink.dll

    File Type: DLL

       Image has the following dependencies:

         postgres.exe
         cygcrypto-1.0.0.dll
         cygwin1.dll
         cygssl-1.0.0.dll
         KERNEL32.dll


I'll build an earlier version to do a comparison just to make sure we're 
seeing the right thing.


cheers

andrew

-- 
Andrew Dunstan                https://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services