id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
12401	UB when sizeof(std::size_t) in floor_log2	viboes	Ion Gaztañaga	"The line 

{{{
      v |= v >> 32; // (*)

}}}

in the following function, should fall in UB, when the sizeof(std::size_t) is 4, isn't it? 


{{{
   inline std::size_t floor_log2 (std::size_t v, integral_constant<std::size_t, 64>)
   {
      static const std::size_t MultiplyDeBruijnBitPosition[64] = {
      63,  0, 58,  1, 59, 47, 53,  2,
      60, 39, 48, 27, 54, 33, 42,  3,
      61, 51, 37, 40, 49, 18, 28, 20,
      55, 30, 34, 11, 43, 14, 22,  4,
      62, 57, 46, 52, 38, 26, 32, 41,
      50, 36, 17, 19, 29, 10, 13, 21,
      56, 45, 25, 31, 35, 16,  9, 12,
      44, 24, 15,  8, 23,  7,  6,  5};

      v |= v >> 1;
      v |= v >> 2;
      v |= v >> 4;
      v |= v >> 8;
      v |= v >> 16;
      v |= v >> 32; // (*)
      return MultiplyDeBruijnBitPosition[((std::size_t)((v - (v >> 1))*0x07EDD5E59A4E28C2ULL)) >> 58];
}
}}}
"	Bugs	closed	To Be Determined	intrusive	Boost 1.61.0	Problem	invalid