Is this other Boost warning harmless and should be ignored when building Bitcoin Core?

Question

In a similar vein to this question I got a new Boost warning when building a PR branch on MacOS.

In file included from /usr/local/include/boost/test/test_tools.hpp:46:
/usr/local/include/boost/test/tools/old/impl.hpp:107:17: warning: comparison of integers of different signs: 'const unsigned int' and 'const int' [-Wsign-compare]
    return left == right;

Is this entirely harmless again? Maybe I should just be configuring with --enable-suppress-external-warnings and ignoring all Boost warnings? A signed integer shouldn't be compared to an unsigned integer though surely?

Answer 1

Is this entirely harmless again?

Quite possibly; you'd need to review the Boost internal code to find out. But in any case, if there is an issue, it's in Boost that this needs to be fixed.

Maybe I should just be configuring with --enable-suppress-external-warnings and ignoring all Boost warnings?

Unless you feel like debugging Boost itself, yes.

A signed integer shouldn't be compared to an unsigned integer though surely?

There is nothing inherently wrong with it. It's an indication that the code could be written in a more obviously correct way likely, but it's perfectly reasonable to encounter this in bug-free code. For example when in the context this is executed, it's known that the signed integer is never negative.