Eric Herman added a comment - 2021-10-25 07:34 - edited From https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html -Wconversion Warn for implicit conversions that may alter a value. This includes conversions between real and integer, like abs( x ) when x is double; conversions between signed and unsigned, like unsigned ui = -1; and conversions to smaller types, like sqrtf (M_PI). Do not warn for explicit casts like abs ((int) x) and ui = (unsigned) -1, or if the value is not changed by the conversion like in abs (2.0). Warnings about conversions between signed and unsigned integers can be disabled by using -Wno-sign-conversion. For C+ , also warn for confusing overload resolution for user-defined conversions; and conversions that never use a type conversion operator: conversions to void, the same type, a base class or a reference to them. Warnings about conversions between signed and unsigned integers are disabled by default in C + unless -Wsign-conversion is explicitly enabled. Warnings about conversion from arithmetic on a small type back to that type are only given with -Warith-conversion.

Jimmy Hú added a comment - 2024-12-13 01:09 While here, how about enabling -Wformat-signedness as well? Linked doc doesn’t say it’s included in -Wconversion or -Wformat (relates to MDEV-21978 ) and doesn’t list it in -Wall .