On Thu, 11 May 2017, Jonathan Wakely wrote: > On 10 May 2017 at 23:14, Daniel Santos wrote: > > Well my primary goal is programming with values that are constant in the > > compiler. There is no language in any C specification (that I'm aware of) > > for a "compile-time constant", but the concept is very important. So just > > because some expression is a compile-time constant doesn't mean we morph > > into a "constant expression" (as per the spec), even with > > __attribute__((const)). > > The C standard says "An implementation may accept other forms of > constant expressions." That means rather than inventing some > "constprop" you could just extend GCC to treat more expressions > involving constants as constant-expressions.
Note that while "other forms" might be accepted in initializers, they would still not be integer constant expressions (see DR#312). -- Joseph S. Myers jos...@codesourcery.com
