Why gcc can compile C++ code but can not link?

I know that c++ code should be compiled and linked by g++, not gcc. But why gcc can still compile c++ source code in spite of lots of c++ keywords in the so开发者_如何学Gource.

By the way, I found that I even can build a shared library by gcc with all c++ code. Why?

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g++ is gcc, it just automatically links to the standard C++ libraries.

If your g++ code depends on the standard libraries (things in the std namespace), you can

1. use the g++ command, and its all automatic
2. use gcc command, and specify the C++ standard libraries explicitly (-lstdc++)

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From the GCC manpage:

   For any given input file, the file name suffix determines what kind of
   compilation is done:

   file.c
       C source code which must be preprocessed.

   .
   .
   .

   file.h
       C, C++, Objective-C or Objective-C++ header file to be turned into
       a precompiled header.

   file.cc
   file.cp
   file.cxx
   file.cpp
   file.CPP
   file.c++
   file.C
       C++ source code which must be preprocessed.  Note that in .cxx, the
       last two letters must both be literally x.  Likewise, .C refers to
       a literal capital C.

What it doesn't do is automatically link to the C++ standard libraries. It's easiest just to use g++ at that point.

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You can link with -lstdc++.