https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82745
--- Comment #4 from helge at penne dot no --- (In reply to Jonathan Wakely from comment #2) > Narrowing conversions only cause a diagnostic in braced-init-list, not in > other contexts. This is how C++ has worked since day one. I must admit that I'm no compiler expert, nor do I have any deep knowledge of the standard. However, I think you must be mistaken here. Try compiling the example I provided (with the command line options that I specified). If you compile it as-is it will pass, but if you remove the comment to enable the last line (the one using unique_ptr instead of make_unique) then it will issue a warning. That line is not using braced-init-list. Btw. that line should probably ideally not have used auto and assignment, but that should not affect the issue here. The compiler will also correctly issue warnings about narrowing conversions on assignment from a "wide" to a "narrow" integer type, including when the signs don't match. It will also warn when narrowing happens when passing parameters to functions. In fact, when enabled it warns about just about any narrowing conversion of ints that I can think of, except those involving std::forward, hence the bug report. Please also have a look a the link I provided to the discussion on the standards forum. I believe these people know a thing or two, and some of them were quite horrified that narrowing in std::forward did not result in a warning. Best regards, H. Penne
