On 10/30/2012 11:56 AM, Vicente J. Botet Escriba wrote:
Le 30/10/12 07:25, Andrey Semashev a écrit :
On Tue, Oct 30, 2012 at 3:15 AM, Vicente J. Botet Escriba <vicente.botet@wanadoo.fr> wrote:
Le 29/10/12 20:16, Jeff Flinn a écrit :
I've just downloaded boost_1_52_0_beta1 and get the warning below in my user code on VC11(I'm using thread which evidently brings in the above libs). I didn't see mention of this in trac. I'm moving forward from 1.47 and from VC8 so I'm not sure if this is an indication of some project setting[s] of mine, or if it should be corrected in the lib?
Thanks, Jeff
6>D:\boost_1_52_0_beta1\boost/ratio/detail/overflow_helpers.hpp(136): warning C4293: '<<' : shift count negative or too big, undefined behavior The concerned code is
static const boost::intmax_t nan = (BOOST_RATIO_INTMAX_C(1) << (sizeof(boost::intmax_t) * CHAR_BIT - 1));
I don't reach to see why the shift count could be negative or too big. If I'm not mistaken, the shifted (positive) value exceeds the intmax_t value range (which is signed) but fits into uintmax_t. E.g. for 64 bit intmax_t it's 1 << 63 while intmax_t range is [-2^63; 2^63 - 1].
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The following program
int main () { std::intmax_t nan= (ULL << (sizeof(intmax_t) * 8 - 1)) ; std::intmax_t max= nan-1 ; std::intmax_t min= -max ; std::cout << std::hex << "max="<< max <<std::endl ; std::cout << std::hex << "min="<< min <<std::endl ; std::cout << std::hex << "nan="<< nan <<std::endl ; std::cout << std::dec << "max="<< max <<std::endl ; std::cout << std::dec << "min="<< min <<std::endl ; std::cout << std::dec << "nan="<< nan <<std::endl ; }
prints
max=7fffffffffffffff min=8000000000000001 nan=8000000000000000 max=9223372036854775807 min=-9223372036854775807 nan=-9223372036854775808
This is what I'm expecting.
That's what I get on VS2012 also.
Maybe to avoid the warning we could replace the nan declaration by
std::intmax_t nan= (ULL << (sizeof(intmax_t) * 8 - 1)) ; by std::intmax_t nan= (std::intmax_t)(1ULL << (sizeof(intmax_t) * 8 - 1)) ;
Note the constant 1ULL instead of 1LL. and of course that the output is the same :)
Please could you try it and see if the warning disappears?
Yep, that clears up the warning. Thanks! static const boost::intmax_t nan = (boost::intmax_t)(1ULL << (sizeof(boost::intmax_t) * CHAR_BIT - 1)) ; The above is what I used locally. Will this get into the boost 1.52.0 release? Thanks again, Jeff