shift-count-overflow possible issue on 64bit type

[Cristiano Di Buduo]

> On Sat, 23 Nov 2019 at 13:56, Jonny Grant <jg@jguk.org> wrote:
> > I see on my 64bit Ubuntu PC that size_t is 8 bytes, that is 64bits,however I see a warning:
> > $ g++-8 -Wall -Wextra -o size_t size_t.cppsize_t.cpp: In function ‘int main()’:size_t.cpp:11:21:
> > warning: left shift count >= width of type[-Wshift-count-overflow]      size_t big =
> > 1<<40;                      ^~
> > 
> > 
> > Same on Godbolt trunk.Is this an issue?
> 
> Why do you expect a different result for these?
> A small = 1 << 40;B big = 1 << 40;
> In both cases the expression is 1 << 40, the type of A or B is irrelevant.

And the default type of a numeric constant is always int. (32 bits).
To make the warning go away, typecast the '1' to a size_t first.