BUG #15266: libpq: PQgetvalue fails with Break at address "0x8000fb50" Signal : SIGSEGV:Segmentation fault)

The following bug has been logged on the website:

Bug reference: 15266
Logged by: bug gy
Email address: buggy(at)trashmail(dot)de
PostgreSQL version: 10.4
Operating system: Windows 10 64 bit
Description:

installation: EnterpriseDB installer 10.4 64 bit

code: 1st example
https://www.postgresql.org/docs/9.1/static/libpq-example.html fails at the
first call to it at line ~100
built with mingw64
gcc "-IC:\\Program Files\\PostgreSQL\\10\\include" -O0 -g3 -Wall -c
-fmessage-length=0 -o testlibpq.o "..\\testlibpq.c"
gcc "-LC:\\Program Files\\PostgreSQL\\10\\lib" -o testcpq.exe testlibpq.o
-lpq -lws2_32

calling PQgetvalue with i=0 j=0 fails with Break at address "0x8000fb50"
with no debug information available, or outside of program code. Thread #1 0
(Suspended : Signal : SIGSEGV:Segmentation fault) 0x8000fb50

console output:
datname datdba encoding datcollate datctype
datistemplate datallowconn datconnlimit datlastsysoid datfrozenxid
datminmxid dattablespace datacl

version 9.6 of libpq.dll & libpq.lib works jsut fine with that code