undefined reference, plz help

[eric lin]

Dear gcc programers:
 
  what may cause compile error (on 4.5.2 or maybe not)
------
 g++ pg49.cpp
/tmp/ccUvNoPf.o: In function `main':
pg49.cpp:(.text+0x42): undefined reference to `IntArray::IntArray(int*, int)'
pg49.cpp:(.text+0x5e): undefined reference to `IntArrayRC::IntArrayRC(int*, int)'
/tmp/ccUvNoPf.o: In function `IntArray::~IntArray()':
pg49.cpp:(.text._ZN8IntArrayD2Ev[_ZN8IntArrayD5Ev]+0xb): undefined reference to `vtable for IntArray'
/tmp/ccUvNoPf.o: In function `IntArrayRC::~IntArrayRC()':
pg49.cpp:(.text._ZN10IntArrayRCD2Ev[_ZN10IntArrayRCD5Ev]+0xb): undefined reference to `vtable for IntArrayRC'
collect2: ld returned 1 exit status
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eric  /* I am happy to supply code I compiled, plz show up your private email address or email me privately */