Fix regression because of adding copy constructor #50
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…onstructors and assignment and move assignment operators for SafeInt<T>. Also solves warning from recent clang using -Wextra
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The change to add a copy constructor from SafeInt to SafeInt caused a regression in some versions of gcc. See MoveRegression() in CompileTest.cpp. It's not clear just why adding a copy constructor might cause this problem, particularly only in some compilers.
The problem came in when running clang with -Wall -Wextra, which caused warnings about a user-supplied assignment operator which didn't have a matching copy constructor. Adding a copy constructor seemed like the right approach, but it caused this regression.
In addition, adding a move constructor and move assignment operator was also tried, and it didn't help. In order to avoid the problem, it seems that none of:
copy constructor
move constructor
assignement operator
move assignment operator
can exist. It's fine that they don't exist, the defaults for all of these do the right thing. In addition, declaring these operators as = default also resulted in errors.
In addition, while clang was building with std=c++17, gcc was not. That's been corrected to ensure the regression test actually works (and general goodness, tests should be equivalent).