Thread safety of std::map for read-only operations

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This will work from multiple threads as long as your map remains the same. The map you use is immutable de facto so any find will actually do a find in a map which does not change.

Here is a relevant link: http://www.sgi.com/tech/stl/thread_safety.html

The SGI implementation of STL is
thread-safe only in the sense that
simultaneous accesses to distinct
containers are safe, and simultaneous
read accesses to to shared containers
are safe. If multiple threads access a
single container, and at least one
thread may potentially write, then the
user is responsible for ensuring
mutual exclusion between the threads
during the container accesses.

You fall into he “simultaneous read accesses to shared containers” category.

Note: this is true for the SGI implementation. You need to check if you use another implementation. Of the two implementations which seem widely used as an alternative, STLPort has built-in thread safety as I know. I don’t know about the Apache implementation though.

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