I have a question about the attributes that GCC is putting on the nexttoward/nextafter builtin functions. This issue started when ToT glibc ran into a problem when building with ToT GCC after Martin Sebor added a patch to GCC that tightened up the attribute checking that GCC does.
The line below no longer compiles cleanly with -Wall -frounding-math -fno-math-errno: extern double nexttoward (double __x, long double __y) __attribute__ ((__nothrow__ )) __attribute__ ((__const__)); When I look at the GCC sources it appears that the attribute on this function (and on the other nextoward and nextafter functions) changesbased on the GCC arguments: -frounding-math -fno-math-errno: __attribute__ ((__pure__)) -fno-math-errno: __attribute__ ((__const__)) -frounding-math: __attribute__ ((__const__)) <neither option>: __attribute__ ((__const__)) I have several questions about this; one is why rounding-math affects the attribute. The other is why the function would be pure with -fno-math-errno but const otherwise. I would think that the -fno-math-errno version would be const (stricter than pure) since it is not setting errno. Finally, how can I check if -frounding-mode is set in the compiler or not. If I want the glibc sources to match the GCC attributes I need to know if -frounding-math is set but there does not seem to be a way to do that. Using -fno-math-errno will set __NO_MATH_ERRNO__ but there does not seem to be an equivelent macro for -frounding-math. Steve Ellcey sell...@cavium.com
