问题
Is there a gcc flag to signal a warning/error when I try to put a double value into an int variable? I currently have -Wall -Wextra -Werror set but I still don't get warned when I (for instance) pass a double to an int parameter, even though I'm losing information.
回答1:
You can use the -Wconversion option. From GCC's manual (emphasis mine):
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.
This is the state uptill GCC 4.8.2, while from GCC 4.9.0 you may also use -Wfloat-conversion for the same.
回答2:
Yes, use the -Wfloat-conversion option:
-Wfloat-conversionWarn for implicit conversions that reduce the precision of a real value. This includes conversions from real to integer, and from higher precision real to lower precision real values. This option is also enabled by
-Wconversion.
来源：https://stackoverflow.com/questions/22198305/is-there-a-gcc-flag-to-catch-integer-truncation