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I (SamJansen) was having a problem after making a C++ shared library. The error produced when I tried to run my application which loaded the library with [dlopen(3)] was:

 mylibrary.so: undefined symbol: __ti13INetTCPSocket

After using [c++filt(1)], we know the undefined symbol is the following:

 INetTCPSocket type_info node

''InetTCPSocket'' is an abstract base class used as in interface. The reason this error was generated was because one function was not declared as abstract, I had forgotten the '= 0' part of the definition.

Another symptom of this is the linker complaining "vtable undefined for class ''x''"
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!!!std::map<>'s crashing

I (PerryLorier) was having a problem after assigning something to a std::map<> the program would crash.
My (abbreviated) code:

 bool operator <(const foo_t &a, const foo_t &b)
 {
    if (a.foo < b.foo) return -1;
    if (a.foo > b.foo) return 1;
    return 0;
  }

 std::map<foo_t,int*> foo_map;

...
  foo_map[[foo]=new int;
  *foo_map[[foo]=6;

And this code crashed.  The reason was that my operator < was wrong.  it voilated the contact of a < operator.  I changed the "bool operator <" to "int cmp" and then defined operator <:
 bool operator <(const foo_t &a, const foo_t &b) { return cmp(a,b) < 0; }
I also recommend adding some assert(3)'s to verify that your operators don't voilate the rules at runtime.



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CategoryProgramming

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Version 4, saved on Thursday, September 23, 2004 3:26:56 pm by PerryLorier

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