Re: 8.2beta1 crash possibly in libpq

On Sun, 2006-10-08 at 17:53 +0200, Magnus Hagander wrote:
> > AFAICT the backtrace and server log is indicating that the
> > crash is happening somewhere in libpq. If someone can help me
> > figure out how to load the libpq symbols into MingW's gdb
> > then I can get a better backtrace if required as I can
> > reproduce this 100% of the time. For reference, the source
> > for the application in question can be found at
> > http://svn.refractions.net/postgis/tags/1.1.4/loader/pgsql2shp.c.
>
> If you figure out how to make gdb actually work on mingw, let us know -
> not many has ever managed to get it wokring, and I don't know of anybody
> who can make it work repeatedly.
>
> That said, libpq builds with Visual C++. Could you try building your
> pgsql2shp with Visual C++ as well, and then use the Visual C++ debugger
> (or windbg, really). They should give working backtraces.
>
> //Magnus

Hi Magnus,

Getting closer I think. I managed to compile a MSVC libpq but it agreed
with the MingW backtrace in that it was jumping into the middle of
nowhere :(

I think I may be getting closer though: I've just done a comparison
build with PostgreSQL 8.1 and noticed that there is an error message is
being emitted regarding PGntuples (which is where the crash is
occuring):

PG 8.1:

mca(at)MCAWINXP ~/postgis/pg81/postgis-1.1.4/loader
$ make
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=81 -c -o shpopen.o
shpopen.c
shpopen.c:176: warning: 'rcsid' defined but not used
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=81 -c -o dbfopen.o
dbfopen.c
dbfopen.c:206: warning: 'rcsid' defined but not used
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=81 -c -o getopt.o
getopt.c
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=81 -c -o shp2pgsql.o
shp2pgsql.c
shp2pgsql.c: In function `utf8':
shp2pgsql.c:1686: warning: passing arg 2 of `libiconv' from incompatible
pointer type
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=81 shpopen.o dbfopen.o
getopt.o shp2pgsql.o -liconv -o shp2pgsql.exe
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=81
-IC:/msys/1.0/home/mca/pg81/REL-81~1.4/include -c pgsql2shp.c
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=81 -c -o PQunescapeBytea.o
PQunescapeBytea.c
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=81 shpopen.o dbfopen.o
getopt.o PQunescapeBytea.o pgsql2shp.o -liconv
C:/msys/1.0/home/mca/pg81/REL-81~1.4/lib/libpq.dll -o pgsql2shp.exe

PG 8.2:

mca(at)MCAWINXP ~/postgis/pg82/postgis-1.1.4/loader
$ make
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=82 -c -o shpopen.o
shpopen.c
shpopen.c:176: warning: 'rcsid' defined but not used
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=82 -c -o dbfopen.o
dbfopen.c
dbfopen.c:206: warning: 'rcsid' defined but not used
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=82 -c -o getopt.o
getopt.c
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=82 -c -o shp2pgsql.o
shp2pgsql.c
shp2pgsql.c: In function `utf8':
shp2pgsql.c:1686: warning: passing arg 2 of `libiconv' from incompatible
pointer type
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=82 shpopen.o dbfopen.o
getopt.o shp2pgsql.o -liconv -o shp2pgsql.exe
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=82
-IC:/msys/1.0/home/mca/pg82/REL-8~1.2BE/include -c pgsql2shp.c
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=82 -c -o PQunescapeBytea.o
PQunescapeBytea.c
gcc -g -Wall -I.. -DUSE_ICONV -DUSE_VERSION=82 shpopen.o dbfopen.o
getopt.o PQunescapeBytea.o pgsql2shp.o -liconv
C:/msys/1.0/home/mca/pg82/REL-8~1.2BE/lib/libpq.dll -o pgsql2shp.exe
Info: resolving _PQntuples by linking to __imp__PQntuples (auto-import)

I think the key part is this line: "Info: resolving _PQntuples by
linking to __imp__PQntuples (auto-import)". Could it be that the linker
cannot find a reference to PQntuples and hence is jumping into random
code? I have verified that PQntuples does exist within libpq.dll using
the Microsoft Dependency Walker though.

Kind regards,

Mark.