On Sat, Nov 2, 2013 at 11:31 AM, Mischa Baars <[email protected]> wrote:
>
> Here's the examples again, now each bug in a separate file. Hope it helps...
>
> Just compile with 'make' and run the executable. The source code is
> documented, so any questions you might have will probably be answered by
> reading the comments.
Thanks for reporting issues with the compiler. This code is short
enough that it would be simpler to just include the code inline in
your e-mail message. For a case this short we don't need a makefile;
just put the command line showing the problem in e-mail.
Unfortunately your test case was not very clear. I think you are
wondering why these two declarations
uint64_t x = 1 << 31;
uint64_t y = (uint64_t) 1 << 31;
do not produce the same values in x and y. That is not a bug in GCC.
It's how the C language works.
In the first line, an integral constant without a suffix has type int.
Left shifting that int value by 31 still gives you a value of type
int. On a system where int is 32 bits, converting a value of type to
a value of type uint64_t sign extends the int.
In the second line, the value is already type uint64_t, and so left
shifting it and then assigning it to a variable of type uint64_t does
not do any sign extension.
Ian
