• eles (22/22) Jul 16 2013 $cat test.cpp:
• Simen Kjaeraas (5/27) Jul 16 2013 This is where integer suffixes can help:
• bearophile (7/9) Jul 16 2013 Bug report/ER:
• eles (8/11) Jul 16 2013 Walter: "Consider all the addressing modes used - they are all
• eles (11/14) Jul 16 2013 Don C.: "There's a root cause issue -- integer overflow is not an
• bearophile (5/11) Jul 16 2013 See:
• bearophile (6/8) Jul 16 2013 A good design for a modern language is to offer safe numbers on
• monarch_dodra (2/4) Jul 16 2013 What do you mean, there is no promotion to int here.

"eles" <eles eles.com> writes:

$cat test.cpp:

#include <iostream>

int main() {
	long long x = 1250000000 * 2;
	std::cout << x << std::endl;
	return 0;
}

g++-generated exe displays: -1794967296

$cat test.d:

import std.stdio;

int main() {
	long x = 1250000000 * 2;
	writefln("%d",x);
	return 0;
}

dmd- and gdc-generated exes display: -1794967296

compiling with g++ at least gives a warning:

warning: integer overflow in expression [-Woverflow]
long long x = 1250000000 * 2;

Both dmd and gdc do not complain in any way.

Isn't the promotion to int so awful? Better ideas? (yes, I know
about casting to long).

"Simen Kjaeraas" <simen.kjaras gmail.com> writes:

On Tue, 16 Jul 2013 12:37:58 +0200, eles <eles eles.com> wrote:

 $cat test.cpp:

 #include <iostream>

 int main() {
 	long long x = 1250000000 * 2;
 	std::cout << x << std::endl;
 	return 0;
 }

 g++-generated exe displays: -1794967296

 $cat test.d:

 import std.stdio;

 int main() {
 	long x = 1250000000 * 2;
 	writefln("%d",x);
 	return 0;
 }

 dmd- and gdc-generated exes display: -1794967296

 compiling with g++ at least gives a warning:

 warning: integer overflow in expression [-Woverflow]
 long long x = 1250000000 * 2;

 Both dmd and gdc do not complain in any way.

 Isn't the promotion to int so awful? Better ideas? (yes, I know
 about casting to long).

This is where integer suffixes can help:

long x = 1250000000L * 2;

-- 
Simen

"bearophile" <bearophileHUGS lycos.com> writes:

eles:

 Isn't the promotion to int so awful? Better ideas? (yes, I know
 about casting to long).

Bug report/ER:
http://d.puremagic.com/issues/show_bug.cgi?id=4835

There is a pull request, but it's currently stalled:
http://d.puremagic.com/issues/show_bug.cgi?id=4835

Bye,
bearophile

"eles" <eles eles.com> writes:

On Tuesday, 16 July 2013 at 11:14:44 UTC, bearophile wrote:
 eles:

 Bye,
 bearophile

Walter: "Consider all the addressing modes used - they are all 
adds, with no overflow checks. Secondly, they all rely on 
wraparound (overflow) arithmetic, after all, that is how 
subtraction is done."

I think the way to go is to introduce "sanitized" integral types,
in conjunction with some compiler flag. If one day Walter agrees
with... This way, everybody is free to use whatever it likes.

"eles" <eles eles.com> writes:

On Tuesday, 16 July 2013 at 11:14:44 UTC, bearophile wrote:
 eles:

 Bye,
 bearophile

Don C.: "There's a root cause issue -- integer overflow is not an
error in general. The paper which bearophile keeps posting, which
he has apparently never read, shows quite convincingly that you
cannot make it an error in a C-family language. There are just
too many legitimate uses of integer wraparound.

eg. int.max + 200 - 300 should not be an error."

Frankly, I keep thinking if FreePascal didn't nail it the good
way: consider all integral values as belonging to the widest
integral type, perform calculation (as if) in that type, then
truncate (if needed) only the final result, on assignment.

"bearophile" <bearophileHUGS lycos.com> writes:

eles:

 Don C.: "There's a root cause issue -- integer overflow is not 
 an error in general. The paper which bearophile keeps posting, 
 which he has apparently never read, shows quite convincingly
 that you cannot make it an error in a C-family language. There
 are just too many legitimate uses of integer wraparound.

 eg. int.max + 200 - 300 should not be an error."

See:
http://d.puremagic.com/issues/show_bug.cgi?id=9850

Bye,
bearophile

"bearophile" <bearophileHUGS lycos.com> writes:

eles:

 Don C.: "There's a root cause issue -- integer overflow is not 
 an error in general.

A good design for a modern language is to offer safe numbers on 
default, and overflowing/modular integral types for the uncommon 
cases where the programmer wants such behaviors.

Bye,
bearophile

"monarch_dodra" <monarchdodra gmail.com> writes:

On Tuesday, 16 July 2013 at 10:37:59 UTC, eles wrote:

 Isn't the promotion to int so awful? Better ideas? (yes, I know
 about casting to long).

What do you mean, there is no promotion to int here.