On 10/04/2013, at 11:06 AM, Nico Williams <n...@cryptonector.com> wrote:
> On Mon, Apr 8, 2013 at 8:52 AM, Alexandr Němec <a.ne...@atlas.cz> wrote: >>> The first warning is harmless and results from a prior datatype change. >>> Dan has already fixed that one. The other four appear to be due to an >>> MSVC compiler bug, since every (i64%int) operation will always yield a value >>> that can fit in an int, no? >> >> Ok, thank for this comment. Of course, you are right, although I wouldn't >> call it a compiler bug. The (i64%int) operation, gives an int result, but >> allocated into an i64 value, so this is why the compiler reports the >> warning. But thanks, it is obvious now, that these warnings can be ignored. > > The compiler is complaining about an int64->int conversion, not the reverse. > > Why on Earth would going from an int (64-bit or smaller) to an int64 > cause a problem? > > No, this is a compiler bug. It is not a compiler bug. It is a failure of the compiler to deduce that the warning is unnecessary. One of the lines in question is: Line 71133 iBuf = p->iReadOff % p->nBuffer; iBuf is an int. p->iReadOff is an i64. p->nBuffer is an int. C's usual arithmetic conversions specify that if either operand of a binary operator is an integer type larger than int then the other operand is first converted to the larger type. Therefore p->nBuffer is converted from int to i64 before doing the modulo operation. We now have i64 % i64, producing a result of type i64. The statement then stores that i64 result into an int. i64 conversion to int without a cast produces the warning in MSVC (if int is 32-bit). If the compiler was smarter, it would pay attention to the fact that the modulus cannot exceed the range of an int, therefore the warning is not necessary. The only reason I can see not to have an explicit cast is that it risks hiding a future bug if the types of the variables are changed. _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
