We make each AIX shared library export all globals found in .o files
that originate in the library. That doesn't include symbols acquired by
-lpgcommon_shlib. That is good on average, but it became a problem for
libpq when commit e6afa8918c moved five
official libpq API symbols into src/common. Fix this by implementing
the SHLIB_EXPORTS mechanism for AIX, so affected libraries export the
same symbols that they export on Linux. This reintroduces symbols
pg_encoding_to_char, pg_utf_mblen, pg_char_to_encoding,
pg_valid_server_encoding, and pg_valid_server_encoding_id. Back-patch
to v13, where the aforementioned commit first appeared. While a minor
release is usually the wrong time to add or remove symbol exports in
libpq or libecpg, we should expect users to want each documented symbol.
Tony Reix
Discussion: https://postgr.es/m/PR3PR02MB6396742E2FC3E77D37A920BC86C79@PR3PR02MB6396.eurprd02.prod.outlook.com
src/port/README
libpgport
=========
libpgport must have special behavior. It supplies functions to both
libraries and applications. However, there are two complexities:
1) Libraries need to use object files that are compiled with exactly
the same flags as the library. libpgport might not use the same flags,
so it is necessary to recompile the object files for individual
libraries. This is done by removing -lpgport from the link line:
# Need to recompile any libpgport object files
LIBS := $(filter-out -lpgport, $(LIBS))
and adding infrastructure to recompile the object files:
OBJS= execute.o typename.o descriptor.o data.o error.o prepare.o memory.o \
connect.o misc.o path.o exec.o \
$(filter strlcat.o, $(LIBOBJS))
The problem is that there is no testing of which object files need to be
added, but missing functions usually show up when linking user
applications.
2) For applications, we use -lpgport before -lpq, so the static files
from libpgport are linked first. This avoids having applications
dependent on symbols that are _used_ by libpq, but not intended to be
exported by libpq. libpq's libpgport usage changes over time, so such a
dependency is a problem. Windows, Linux, AIX, and macOS use an export
list to control the symbols exported by libpq.
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