The linker doesn't find dynamic (shared object) libraries in /usr/lib

[Uqbar]

This is the (usual) test program:
/*File: p.c*/
#include <stdio.h>

int main() {
  printf( "Hello world!\n" );
  return 0;
}
/*EOF*/

If I compile it like this:
gcc -o p p.c -lpq # I add an extra useless library to be linked
Averything works fine. I currently have this:
~ ls -l /usr/lib/libpq*
-rw-r--r-- 1 root root 242018 mar 6 12:50 /usr/lib/libpq.a
lrwxrwxrwx 1 root root 12 mar 6 12:49 /usr/lib/libpq.so -> libpq.so.5.4
lrwxrwxrwx 1 root root 12 mar 6 12:49 /usr/lib/libpq.so.5 -> libpq.so.5.4
-rw-r--r-- 1 root root 163308 mar 6 12:50 /usr/lib/libpq.so.5.4

So both shared object and static libraries are present.
If I try instead this compilation:

~ gcc -o p p.c -lsox
/usr/bin/ld: cannot find -lsox
collect2: ld returned 1 exit status

where there is no static libary for libsox:

~ ls -l /usr/lib/libsox*
lrwxrwxrwx 1 root root 15 dic 27 22:39 /usr/lib/libsox.so.1 -> libsox.so.1.0.0
-rw-r--r-- 1 root root 562436 dic 27 22:39 /usr/lib/libsox.so.1.0.0

It used to work fine as of 11.10.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: g++ 4:4.6.3-1ubuntu5
ProcVersionSignature: Ubuntu 3.2.0-24.38-generic-pae 3.2.16
Uname: Linux 3.2.0-24-generic-pae i686
ApportVersion: 2.0.1-0ubuntu7
Architecture: i386
Date: Fri May 11 09:55:12 2012
InstallationMedia: Kubuntu 11.10 "Oneiric Ocelot" - Release i386 (20111012)
SourcePackage: gcc-defaults
UpgradeStatus: Upgraded to precise on 2012-04-27 (14 days ago)

[Matthias Klose (doko)]

you are missing the -dev package fox sox

[Uqbar (uqbar)]

If you had read the original report, you could have seen two major things.

1. The shared library file(s) for libsox were in place and readable

2. After two years and a few releases maybe something has been fixed.

It is an invalid bug indeed, as it doesn't make sense any more.