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Asked: 2026-05-11T02:40:13+00:00

For two threads manipulating a container map for example, what the correct way to

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For two threads manipulating a container map for example, what the correct way to test whether an iterator still valid (for performance reason) ?
Or would be of only indirect way that this can be done. The sample code for this :

#define _SECURE_SCL 1 //http://msdn2.microsoft.com/en-us/library/aa985973.aspx #define _SECURE_SCL_THROWS 1  #include 'map' #include 'string' #include 'exception' #include 'iostream'  using namespace std;  void main(void) {     map<string, string> map_test;     map<string, string>::iterator iter_map_test;      map_test [ 'AAAAA' ] = '11111';     map_test [ 'BBBBB' ] = '22222';     map_test [ 'CCCCC' ] = '33333';      iter_map_test = map_test.find ('BBBBB');      map_test.erase ('BBBBB');      try     {         string value = (*iter_map_test).second;     }     catch ( exception & e )     {             cout << e.what() << endl;     }     catch ( ... )     {             cout << 'generic exception.' << endl;     } }
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1 Answer

  1. std::maps are not at all thread-safe. You’ll end up with much worse problems than invalidated iterators, if you have more than one thread at a time modifying the same map. I don’t even think you have a guarantee that you can read anything out of a map while it’s being modified by another thread.

    Some pages on the STL and threading:

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