On 5/7/2019 12:14 PM, Thiago Macieira wrote:
On Tuesday, 7 May 2019 05:13:33 PDT Ola Røer Thorsen wrote:
lør. 4. mai 2019 kl. 17:51 skrev Thiago Macieira <[email protected]
No, the size of something definitely fits in int on 32-bit systems. And
why do
you need to do any static_cast in the first place?
We build our code using gcc with the options "-Wall -Wextra -Werror" and
this leads us to have to use static_cast for example when comparing int and
unsigned int (or std::size_t). A mix of using std::array, std::string and
QVector/QByteArray often gives a few extra static casts, not that it
bothers me too much.
Well, that's your problem: mixing the APIs. The committee has recognised that
it should have used signed types, but it can't change now.
If there's ever an STL2 (std2 namespace), it'll use signed.
It's not just mixing C++ APIs. It is interfacing with devices which use
unsigned octates in groups for the size followed by a contiguous block
of octates for the data. When they accept text input it has to be sent
this way and when they communicate text responses it comes back this way.
There are also the big data blocks like X-RAY/MRI images and such which
need to be loaded into larger than signed int containers for manipulation.
I haven't dug under the hood but I wonder if this impacts memory mapping of
files. Maybe not if there is no container.
uchar * dl_map = m_libraryFile.map(0, m_libraryFile.size());
====
developer@developer-U18-64-VirtualBox:~$ ./test_sizes
short int: 2
int: 4
long int: 8
long long int: 8
size_t: 8
void*: 8
unsigned int: 4
uint32_t: 4
uint64_t: 8
void *: 8
unsigned long: 8
uint32_t max: 4294967295
uint max: 4294967295
uint64_t max: 18446744073709551615
====
developer@developer-U18-64-VirtualBox:~$ cat test_sizes.c
#include <stdio.h>
#include <limits.h>
#include <stdint.h>
int main() {
printf( " short int: %zd\n" , sizeof(short int) ) ;
printf( " int: %zd\n" , sizeof(int) ) ;
printf( " long int: %zd\n", sizeof(long int) ) ;
printf( "long long int: %zd\n", sizeof(long long int) ) ;
printf( " size_t: %zd\n", sizeof(size_t) ) ;
printf( " void*: %zd\n", sizeof(void *) ) ;
printf( " unsigned int: %zd\n", sizeof(unsigned int));
printf( " uint32_t: %zd\n", sizeof(uint32_t));
printf( " uint64_t: %zd\n", sizeof(uint64_t));
printf( " void *: %zd\n", sizeof(void *));
printf( "unsigned long: %zd\n", sizeof(unsigned long) );
printf( " uint32_t max: %u\n", UINT32_MAX);
printf( " uint max: %u\n", UINT_MAX);
printf( " uint64_t max: %lu\n", UINT64_MAX);
return 0;
}developer@developer-U18-64-VirtualBox:~$
=====
developer@developer-U18-64-VirtualBox:~$ lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
=====
The ptrdiff_t comment earlier is a red herring.
https://en.cppreference.com/w/cpp/types/ptrdiff_t
typedef /*implementation-defined*/ ptrdiff_t;
=====
The static cast issue is a problem in the embedded device world. Well,
it is an annoyance in the embedded device world. It's a documentation
and defending your honor nightmare in regulated device world such as
medical devices. Probably nuke systems as well.
Some shops won't or cannot let you use an int.
If they are changing from int to q-whatever defined type there will
probably be some compilation cleanup anyway so unsigned wouldn't be bad
unless someone is cheating somewhere and initializing size to -1
--
Roland Hughes, President
Logikal Solutions
(630) 205-1593
http://www.theminimumyouneedtoknow.com
http://www.infiniteexposure.net
http://www.johnsmith-book.com
http://www.logikalblog.com
http://www.interestingauthors.com/blog
http://lesedi.us
_______________________________________________
Interest mailing list
[email protected]
https://lists.qt-project.org/listinfo/interest
