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Groups > comp.lang.c > #387396
| From | Michael S <already5chosen@yahoo.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: how cast works? |
| Date | 2024-08-08 19:32 +0300 |
| Organization | A noiseless patient Spider |
| Message-ID | <20240808193203.00006287@yahoo.com> (permalink) |
| References | <v8vlo9$2oc1v$1@dont-email.me> <slrnvb7kis.28a.dan@djph.net> <v929ah$3u7l7$1@dont-email.me> <v92gt1$e1l$1@dont-email.me> |
On Thu, 8 Aug 2024 14:23:44 +0100
Bart <bc@freeuk.com> wrote:
> On 08/08/2024 12:14, Thiago Adams wrote:
> > On 07/08/2024 17:00, Dan Purgert wrote:
> >> On 2024-08-07, Thiago Adams wrote:
> >>> How cast works?
> >>> Does it changes the memory?
> >>> For instance, from "unsigned int" to "signed char".
> >>> Is it just like discarding bytes or something else?
> >>> [...]
> >>
> >> I don't know what happens when you're changing datatype lengths,
> >> but if they're the same length, it's just telling the compiler
> >> what the variable should be treated as (e.g. [8-bit] int to char)
> >>
> >>>
> >>> I also would like to understand better signed and unsigned.
> >>> There is no such think as "signed" or "unsigned" register, right?
> >>>
> >>
> >> "Signed" just means the first bit indicates negative.
> >>
> >> So an "unsigned" 8 bit integer will have the 256 values ranging
> >> from
> >>
> >> 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 = 0
> >> (0b00000000)
> >>
> >> TO
> >>
> >> 128 + 64 + 32 + 16 + 8 +4 + 2 + 1 = 255
> >> (0b11111111)
> >>
> >>
> >> Whereas a "signed" 8 bit integer will have the 256 values ranging
> >> from
> >>
> >> (-128) + 0 + 0 + 0 + 0 + 0 + 0 + 0 = -128
> >> (0b10000000)
> >>
> >> TO
> >>
> >> 0 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 127
> >> (0b01111111)
> >>
> >> At least in two's compliment (but that's the way it's done in C)
> >>
> >>
> >>> How about floating point?
> >>
> >> Floating point is a huge mess, and has a few variations for
> >> encoding; though I think most C implementations use the one from
> >> the IEEE on 1985 (uh, IEEE754, I think?)
> >>
> >
> >
> >
> > I didn't specify properly , but my question was more about floating
> > point registers. I think in this case they have specialized
> > registers.
>
>
> Try godbolt.org. Type in a fragment of code that does different kinds
> of casts (it needs to be well-formed, so inside a function), and see
> what code is produced with different C compilers.
>
> Use -O0 so that the code isn't optimised out of existence, and so
> that you can more easily match it to the C source.
>
>
I'd recommend an opposite - use -O2 so the cast that does nothing
optimized away.
int foo_i2i(int x) { return (int)x; }
int foo_u2i(unsigned x) { return (int)x; }
int foo_b2i(_Bool x) { return (int)x; }
int foo_d2i(double x) { return (int)x; }
etc
https://godbolt.org/z/GWjbcG4GT
Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar
how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-07 08:28 -0300
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-07 08:33 -0300
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-07 13:13 -0700
Re: how cast works? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-11 17:43 -0700
Re: how cast works? Vir Campestris <vir.campestris@invalid.invalid> - 2024-08-12 11:51 +0100
Challenge/exercise problem - signum() function Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-12 08:17 -0700
Re: Challenge/exercise problem - signum() function Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2024-08-12 16:07 +0000
Re: Challenge/exercise problem - signum() function Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-12 09:57 -0700
Re: how cast works? Dan Purgert <dan@djph.net> - 2024-08-07 20:00 +0000
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-07 13:26 -0700
Re: how cast works? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-08-07 23:00 +0000
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-08 08:14 -0300
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-08 14:23 +0100
Re: how cast works? Michael S <already5chosen@yahoo.com> - 2024-08-08 19:32 +0300
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-08 14:11 -0300
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-08 18:29 +0100
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-08 14:50 -0300
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-08 14:57 -0300
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-08 19:01 +0100
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-08 15:13 -0300
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-08 12:29 -0700
Re: how cast works? David Brown <david.brown@hesbynett.no> - 2024-08-08 19:58 +0200
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-08 20:09 +0100
Re: how cast works? David Brown <david.brown@hesbynett.no> - 2024-08-09 00:32 +0200
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-08 16:14 -0700
Re: how cast works? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-08-09 02:47 +0000
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-08 22:55 -0700
Re: how cast works? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-08-09 02:08 -0400
Re: how cast works? David Brown <david.brown@hesbynett.no> - 2024-08-09 18:16 +0200
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 12:18 -0700
Re: how cast works? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-11 17:07 -0700
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-11 20:14 -0700
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-09 01:56 +0100
Re: how cast works? David Brown <david.brown@hesbynett.no> - 2024-08-09 19:08 +0200
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-10 11:03 +0100
Re: how cast works? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-08-09 02:45 +0000
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-08 12:42 -0700
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-08 17:34 -0300
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-08 22:41 +0100
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-08 16:17 -0700
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-09 11:04 +0100
Re: how cast works? David Brown <david.brown@hesbynett.no> - 2024-08-09 19:12 +0200
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-12 15:36 +0100
Re: how cast works? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-08-09 13:57 -0400
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-09 21:59 +0100
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 14:47 -0700
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-10 00:32 +0100
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 17:12 -0700
Re: how cast works? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-08-09 18:29 -0400
Re: how cast works? David Brown <david.brown@hesbynett.no> - 2024-08-13 11:18 +0200
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-13 11:34 +0100
Re: how cast works? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-08-13 07:51 -0400
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-13 14:01 +0100
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-13 12:46 -0700
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-13 21:51 +0100
Re: how cast works? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-13 16:46 -0700
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-14 00:56 +0100
Re: how cast works? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-18 03:37 -0700
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 14:29 -0700
Re: how cast works? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-08-09 18:35 -0400
Re: how cast works? Kaz Kylheku <643-408-1753@kylheku.com> - 2024-08-09 21:30 +0000
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 14:57 -0700
Re: how cast works? Kaz Kylheku <643-408-1753@kylheku.com> - 2024-08-09 23:14 +0000
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 16:58 -0700
Re: how cast works? Kaz Kylheku <643-408-1753@kylheku.com> - 2024-08-10 00:06 +0000
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 17:27 -0700
Re: how cast works? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-08-09 20:31 -0400
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-10 01:11 +0100
Re: how cast works? David Brown <david.brown@hesbynett.no> - 2024-08-13 11:23 +0200
Re: how cast works? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-11 17:32 -0700
Re: how cast works? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-08-09 18:35 -0400
Re: how cast works? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-11 17:27 -0700
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 12:23 -0700
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-09 21:31 +0100
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 13:49 -0700
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-09 22:01 +0100
Re: how cast works? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-12 00:33 -0700
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-12 12:21 +0100
Re: how cast works? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-11 17:46 -0700
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-12 02:00 +0100
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-11 20:23 -0700
Re: how cast works? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-11 20:37 -0700
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-11 21:33 -0700
Re: how cast works? Ben Bacarisse <ben@bsb.me.uk> - 2024-08-12 16:57 +0100
Re: how cast works? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-12 10:04 -0700
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-12 13:35 -0700
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-09 07:57 -0300
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-09 16:25 +0100
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 12:06 -0700
Re: how cast works? David Brown <david.brown@hesbynett.no> - 2024-08-09 19:20 +0200
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-09 15:54 -0300
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-09 16:05 -0300
Re: how cast works? David Brown <david.brown@hesbynett.no> - 2024-08-09 21:43 +0200
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 13:28 -0700
Re: how cast works? David Brown <david.brown@hesbynett.no> - 2024-08-09 22:01 +0200
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-10 11:17 +0100
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-10 10:15 -0300
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-10 17:14 +0100
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-10 20:01 -0300
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-10 17:10 -0700
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-11 09:23 -0300
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-11 13:30 +0100
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-11 14:16 -0300
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-11 13:38 -0700
Re: how cast works? Bart <bc@freeuk.com> - 2024-08-12 12:24 +0100
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 13:26 -0700
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-09 18:01 -0300
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 14:53 -0700
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-09 12:03 -0700
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-09 16:22 -0300
Re: how cast works? David Brown <david.brown@hesbynett.no> - 2024-08-09 00:36 +0200
Re: how cast works? Dan Purgert <dan@djph.net> - 2024-08-08 14:08 +0000
Re: how cast works? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-08-09 02:42 +0000
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-07 13:08 -0700
Re: how cast works? Thiago Adams <thiago.adams@gmail.com> - 2024-08-08 08:35 -0300
Re: how cast works? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2024-08-08 12:39 -0700
Re: how cast works? James Kuyper <jameskuyper@alumni.caltech.edu> - 2024-08-08 18:40 -0400
Re: how cast works? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2024-08-11 17:15 -0700
Is there an audio book version (Was: how cast works?) gazelle@shell.xmission.com (Kenny McCormack) - 2024-08-08 16:19 +0000
Re: how cast works? Lawrence D'Oliveiro <ldo@nz.invalid> - 2024-08-07 23:03 +0000
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