Thread: more on undefined reference to 'pg_detoast_datum' and libpq
Apparently in PosgreSQL 7.2.3 (the Redhat 7.3 version, which has some patching involved), pg_detoast_datum is defined in fmgr backend code, but this function is not defined anywhere in any library, especially not libpq. It is the necessity to use fmgr.h functions that brings about the need to have pg_detoast_datum. The V1 interface itself requires fmgr.h, this is where PG_FUNCTION_INFO_V1 is declared, along with other V1 macros. My guess is that pg_detoast_datum should be in a library somewhere, but manually compiling PostgreSQL 7.2.3 source with unstripped libraries shows that no dynamic library produced from the source build contains the necessary functions. There does not appear to be any libfmgr.so (of any version), unless there is some configure option I am missing. How do I get around this without using non-Redhat packages and without forcing users to install another version of PostgreSQL? At this point it looks like there is no choice but to use the V0 interface to libpq and develop separate projects for other versions of linux PostgreSQL that have more recent versions. D. Stimits
"D. Stimits" <stimits@comcast.net> writes:
> Apparently in PosgreSQL 7.2.3 (the Redhat 7.3 version, which has some
> patching involved), pg_detoast_datum is defined in fmgr backend code,
> but this function is not defined anywhere in any library, especially not
> libpq.
Of course not; it's a backend function. Your problem is that you are
trying to build a server-side function as though it were a client
application. You're linking to an inappropriate set of libraries.
See the contrib modules for numerous examples of correct link setup
for server-side functions.
regards, tom lane
Tom Lane wrote: > "D. Stimits" writes: > > >Apparently in PosgreSQL 7.2.3 (the Redhat 7.3 version, which has some > >patching involved), pg_detoast_datum is defined in fmgr backend code, > >but this function is not defined anywhere in any library, especially not > >libpq. > > > Of course not; it's a backend function. Your problem is that you are > trying to build a server-side function as though it were a client > application. You're linking to an inappropriate set of libraries. > See the contrib modules for numerous examples of correct link setup > for server-side functions. > > regards, tom lane > My attempt to try linking against some of the client libraries was to find a link source for CurrentMemoryContext and MemoryContextAlloc. The headers for backend development include prototypes as extern for many functions, such as those above. It's painfully obvious that glibc does not provide these definitions, and it is obvious also that the client libraries do not implement these. My question is, where the heck is CurrentMemoryContext and MemoryContextAlloc provided as an implementation which I can link with? It looks like the Redhat 7.3 (PostgreSQL 7.2.3) devel rpm package is missing the library needed. Or perhaps there is no such library, and I'd be required to drop my code into the complete source of the SQL server itself, which is most inconvenient. How the heck do I find an implentation of CurrentMemoryContext and MemoryContextAlloc? Running ldd on sample contrib libraries leads me to believe that in order to build this code, I must have a built full PostgreSQL source installed and configured, and that these functions are not available as a linkable library. Which .o object file would I link? Why isn't CurrentMemoryContext or MemoryContextAlloc available in a linkable library instead? D. Stimits
"D. Stimits" <stimits@comcast.net> writes:
> ... My question is, where the heck is
> CurrentMemoryContext and MemoryContextAlloc provided as an
> implementation which I can link with?
They're inside the backend, and you don't --- you are not trying to
build a standalone executable with no unresolved symbols, but a shared
library that can be successfully loaded into the backend. It's okay
for such a library to have unresolved references to symbols that will be
resolved at load time.
regards, tom lane
D. Stimits wrote: > My attempt to try linking against some of the client libraries was to > find a link source for CurrentMemoryContext and MemoryContextAlloc. The > headers for backend development include prototypes as extern for many > functions, such as those above. It's painfully obvious that glibc does > not provide these definitions, and it is obvious also that the client > libraries do not implement these. My question is, where the heck is > CurrentMemoryContext and MemoryContextAlloc provided as an > implementation which I can link with? It looks like the Redhat 7.3 > (PostgreSQL 7.2.3) devel rpm package is missing the library needed. Or > perhaps there is no such library, and I'd be required to drop my code > into the complete source of the SQL server itself, which is most > inconvenient. How the heck do I find an implentation of > CurrentMemoryContext and MemoryContextAlloc? Running ldd on sample > contrib libraries leads me to believe that in order to build this code, > I must have a built full PostgreSQL source installed and configured, and > that these functions are not available as a linkable library. Which .o > object file would I link? Why isn't CurrentMemoryContext or > MemoryContextAlloc available in a linkable library instead? I am still confused about what you're trying to build. Anyhow, CurrentMemoryContext and MemoryContextAlloc are global symbols of the servers backend memory management system. If you're building a function that you plan to load dynamically into the database server process via CREATE FUNCTION, then you will definitely NOT link against libpq and should follow the plenty examples as suggested by Tom. If you are developing a client application that will connect to a backend via the libpq client library, than you don't have these functions/globals available. We do not provide this memory management system as a standalone, linkable library. Jan -- #======================================================================# # It's easier to get forgiveness for being wrong than for being right. # # Let's break this rule - forgive me. # #================================================== JanWieck@Yahoo.com #