Does program need additional symbols from .so shared library except those declared in header file?
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Published on 2010-03-03T08:48:02Z
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2010/03/14
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In C programming, I thought that a object file can be successfully linked with a .so file as long as the .so file offers all symbols which have been declared in the header file.
Suppose I have foo.c, bar.h and two libraries libbar.so.1 and libbar.so.2. The implementation of libbar.so.1 and libbar.so.2 is totally different, but I think it's OK as long as they both offers functions declared in bar.h.
I linked foo.o with libbar.so.1 and produced an executable: foo.bin. This executable worked when libbar.so.1 is in LD_LIBRARY_PATH.(of course a symbolic link is made as libbar.so) However, when I change the symbolic link to libbar.so.2, foo.bin could not run and complainted this:
undefined symbol: _ZSt4cerr
I found this symbol type is 'B' and it does not appear in libbar.so.2. Obviously this symbol has nothing to do with those functions I decared in bar.h. What's wrong here?
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