Обсуждение: Postgres installed but my C programs won't compile

I had no trouble installing Postgres 6.4 on my RedHat 5.1 Linux machine.
However, the C programs I had previously written to access the SQL
database were not returning the correct values. I tried to make some
changes and re-compile the program but got the following error when I
tried to run the re-compiled program:

[reina ~/c_programs]$ cc process_kinematics.c -o PROCESS_KINEMATICS $SQL
matrix_tools.c gcvspl.o -lm
[reina ~/c_programs]$ PROCESS_KINEMATICS
PROCESS_KINEMATICS: error in loading shared libraries
libpq.so.2.0: cannot open shared object file: No such file or directory

It looks as though SQL can't find my shared libraries for Postgres
anymore. Does anybody know why?

I tried copying my 6.3.2 version back into the proper directories and
the program will compile and re-run correctly.

Anyone know what to do?

Thanks.
-Tony

"G. Anthony Reina" wrote:
  >I had no trouble installing Postgres 6.4 on my RedHat 5.1 Linux machine.
  >However, the C programs I had previously written to access the SQL
  >database were not returning the correct values. I tried to make some
  >changes and re-compile the program but got the following error when I
  >tried to run the re-compiled program:
  >
  >[reina ~/c_programs]$ cc process_kinematics.c -o PROCESS_KINEMATICS $SQL
  >matrix_tools.c gcvspl.o -lm
  >[reina ~/c_programs]$ PROCESS_KINEMATICS
  >PROCESS_KINEMATICS: error in loading shared libraries
  >libpq.so.2.0: cannot open shared object file: No such file or directory
  >
  >It looks as though SQL can't find my shared libraries for Postgres
  >anymore. Does anybody know why?
  >
  >I tried copying my 6.3.2 version back into the proper directories and
  >the program will compile and re-run correctly.

The library version number changed at 6.4.  If your 6.3.2 was from an
rpm and you have compiled this one for yourself, it is possible that the
libraries have ended up in different places.  On Debian, packages
put libraries in /usr/lib, for example, whereas, by default, PostgreSQL
install puts them in /usr/local/lib.

Try adding -l/usr/local/lib to the compile line.

--
Oliver Elphick                                Oliver.Elphick@lfix.co.uk
Isle of Wight                              http://www.lfix.co.uk/oliver
               PGP key from public servers; key ID 32B8FAA1
                 ========================================
     "If my people, which are called by my name, shall
      humble themselves, and pray, and seek my face, and
      turn from their wicked ways; then will I hear from
      heaven, and will forgive their sin, and will heal
      their land."               II Chronicles 7:14

"G. Anthony Reina" <reina@nsi.edu> writes:
> I had no trouble installing Postgres 6.4 on my RedHat 5.1 Linux machine.
> However, the C programs I had previously written to access the SQL
> database were not returning the correct values. I tried to make some
> changes and re-compile the program but got the following error when I
> tried to run the re-compiled program:
> libpq.so.2.0: cannot open shared object file: No such file or directory
> It looks as though SQL can't find my shared libraries for Postgres
> anymore. Does anybody know why?

You may need to re-run ldconfig, or something like that, to get the
system to know where that library is.  This is pretty OS-dependent,
but there is some generic advice in the INSTALL instructions.
(BTW, if you find you can extend or improve on the INSTALL advice,
please send in better text...)

Things to check to try to debug this:

1. Does psql fire up for you, or does it fail with the same error?

2. You might try examining your executable with ldd to see if its shared
library dependency info looks reasonable.  (Assuming that psql works,
compare the output for psql.)

If all else fails, you can link libpq.a statically into your program
with an appropriate link-time switch (-Bstatic, I think, on Linux).
But it's better to get the sharedlib support working.

            regards, tom lane