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digitalmars.D - Static Analysis Tooling / Effective D

reply "Brian Schott" <briancschott gmail.com> writes:
I've checked in code to the DScanner project that gives it some 
basic static analysis capabilities. When run with the 
--styleCheck option, it will warn about a few things like empty 
declarations, implicit string concatenation, classes with 
lowercase_names, catching "Exception", and a few other things.

There's a small feature wishlist in the project's README, but I'd 
like to get some opinions from the newsgroup: What kinds of 
errors have you seen in your code that you think a static 
analysis tool could help with?
Jan 20 2014
next sibling parent "Suliman" <evermind live.ru> writes:
It would be perfect have plugin for any Text Editor like Sublime
Jan 20 2014
prev sibling next sibling parent "Volcz" <volcz kth.se> writes:
On Tuesday, 21 January 2014 at 04:34:57 UTC, Brian Schott wrote:

 I've checked in code to the DScanner project that gives it some 
 basic static analysis capabilities. When run with the 
 --styleCheck option, it will warn about a few things like empty 
 declarations, implicit string concatenation, classes with 
 lowercase_names, catching "Exception", and a few other things.

 There's a small feature wishlist in the project's README, but 
 I'd like to get some opinions from the newsgroup: What kinds of 
 errors have you seen in your code that you think a static 
 analysis tool could help with?


I don't have any D specific errors that I keep repeating. I use 
SonarQube at work with Java. Here is a list of some of the 
"rules" that I use:
https://github.com/SonarSource/sonar-java/tree/master/java-checks/src/main/java/org/sonar/java/checks
Jan 20 2014
prev sibling next sibling parent reply Walter Bright <newshound2 digitalmars.com> writes:
On 1/20/2014 8:34 PM, Brian Schott wrote:

 I've checked in code to the DScanner project that gives it some basic static
 analysis capabilities. When run with the --styleCheck option, it will warn
about
 a few things like empty declarations, implicit string concatenation, classes
 with lowercase_names, catching "Exception", and a few other things.

 There's a small feature wishlist in the project's README, but I'd like to get
 some opinions from the newsgroup: What kinds of errors have you seen in your
 code that you think a static analysis tool could help with?


Automated source code formatting would be nice (and it's not as easy as it
looks).
Jan 21 2014
next sibling parent reply "Dicebot" <public dicebot.lv> writes:
On Tuesday, 21 January 2014 at 08:01:47 UTC, Walter Bright wrote:

 Automated source code formatting would be nice (and it's not as 
 easy as it looks).


It has nothing to do with static analysis.
Jan 21 2014
parent reply Walter Bright <newshound2 digitalmars.com> writes:
On 1/21/2014 12:54 AM, Dicebot wrote:

 On Tuesday, 21 January 2014 at 08:01:47 UTC, Walter Bright wrote:

 Automated source code formatting would be nice (and it's not as easy as it
 looks).


 It has nothing to do with static analysis.


Coverity (a static analyzer) does checks based on whitespace indentation. It's 
not a great leap from there to just format it.
Jan 21 2014
next sibling parent "Dicebot" <public dicebot.lv> writes:
On Tuesday, 21 January 2014 at 09:22:16 UTC, Walter Bright wrote:

 Coverity (a static analyzer) does checks based on whitespace 
 indentation. It's not a great leap from there to just format it.


One can also say that it is not a huge leap for compiler to do 
the same. Of course all those tool can share a lot of 
implementation and often are used together, but I think there is 
a value in keeping unrelated functionality separately available. 
UNIX-way ftw.
Jan 21 2014
prev sibling parent "bearophile" <bearophileHUGS lycos.com> writes:
Walter Bright:


 Coverity (a static analyzer) does checks based on whitespace 
 indentation.


This is good to have.

Perhaps splitting the compiler in some parts could help people 
create such tools.

Bye,
bearophile
Jan 21 2014
prev sibling parent "Daniel Murphy" <yebbliesnospam gmail.com> writes:
"Walter Bright"  wrote in message news:lbl9ha$i85$1 digitalmars.com...

 Automated source code formatting would be nice (and it's not as easy as it 
 looks).


That would be great, we could run it on the generated ddmd source and I 
wouldn't have to fix all the remaining formatting bugs!
Jan 21 2014
prev sibling next sibling parent reply "Dicebot" <public dicebot.lv> writes:
On Tuesday, 21 January 2014 at 04:34:57 UTC, Brian Schott wrote:

 I've checked in code to the DScanner project that gives it some 
 basic static analysis capabilities. When run with the 
 --styleCheck option, it will warn about a few things like empty 
 declarations, implicit string concatenation, classes with 
 lowercase_names, catching "Exception", and a few other things.

 There's a small feature wishlist in the project's README, but 
 I'd like to get some opinions from the newsgroup: What kinds of 
 errors have you seen in your code that you think a static 
 analysis tool could help with?


I'd personally love to see most of existing DMD warnings moved to 
DScanner and, after it get some recognition, removed from 
compiler completely. That, of course, implies some way to tune 
output for specific project, supressing some of detection 
patterns.

That reminds me about related topic - do we have any pragma / 
attribute reserved for external tools? So that one could, for 
example, disable analysis error for specific part of sourc code 
without disabling it globally?
Jan 21 2014
next sibling parent reply "Brian Schott" <briancschott gmail.com> writes:
On Tuesday, 21 January 2014 at 08:58:19 UTC, Dicebot wrote:

 That reminds me about related topic - do we have any pragma / 
 attribute reserved for external tools? So that one could, for 
 example, disable analysis error for specific part of sourc code 
 without disabling it globally?


I assume you're talking about something like  SuppressWarnings in 
Java? 
http://docs.oracle.com/javase/7/docs/api/java/lang/SuppressWarnings.html
Jan 21 2014
parent "Dicebot" <public dicebot.lv> writes:
On Tuesday, 21 January 2014 at 09:11:37 UTC, Brian Schott wrote:

 On Tuesday, 21 January 2014 at 08:58:19 UTC, Dicebot wrote:

 That reminds me about related topic - do we have any pragma / 
 attribute reserved for external tools? So that one could, for 
 example, disable analysis error for specific part of sourc 
 code without disabling it globally?


 I assume you're talking about something like  SuppressWarnings 
 in Java? 
 http://docs.oracle.com/javase/7/docs/api/java/lang/SuppressWarnings.html


I was thinking of a more fine-tuned thing, similar to gcc 
`__attribute__ (unused)` but generalised a bit to not interfere 
with normal attributes by using reserved namespace.

Single  SuppressWarnings (analysis reports in our case) can be a 
simpler compromise though.
Jan 21 2014
prev sibling parent reply Walter Bright <newshound2 digitalmars.com> writes:
On 1/21/2014 12:58 AM, Dicebot wrote:

 That reminds me about related topic - do we have any pragma / attribute
reserved
 for external tools? So that one could, for example, disable analysis error for
 specific part of sourc code without disabling it globally?


Since we have user defined attributes, I don't see how anything further needs
to 
be added to the language.
Jan 21 2014
parent reply "Dicebot" <public dicebot.lv> writes:
On Tuesday, 21 January 2014 at 09:30:45 UTC, Walter Bright wrote:

 On 1/21/2014 12:58 AM, Dicebot wrote:

 That reminds me about related topic - do we have any pragma / 
 attribute reserved
 for external tools? So that one could, for example, disable 
 analysis error for
 specific part of sourc code without disabling it globally?


 Since we have user defined attributes, I don't see how anything 
 further needs to be added to the language.


See "reserved namespace" reference. It does not need any special 
support from the language itself but some support from spec that 
will ensure that those attributes won't conflict with user code 
and other tools will be helpful. Probably even in form of 
guideline, not a rule.
Jan 21 2014
next sibling parent Jacob Carlborg <doob me.com> writes:
On 2014-01-21 10:33, Dicebot wrote:


 See "reserved namespace" reference. It does not need any special support
 from the language itself but some support from spec that will ensure
 that those attributes won't conflict with user code and other tools will
 be helpful. Probably even in form of guideline, not a rule.


The answer to this is usually that each tool should use its own 
attributes and that fully qualified names should properly disambiguate 
the attributes. Although, in this case it might be asking a bit too much 
for a tool to be able to properly figure out fully qualified names of 
symbol names.

-- 
/Jacob Carlborg
Jan 21 2014
prev sibling parent reply Walter Bright <newshound2 digitalmars.com> writes:
On 1/21/2014 1:33 AM, Dicebot wrote:

 See "reserved namespace" reference. It does not need any special support from
 the language itself but some support from spec that will ensure that those
 attributes won't conflict with user code and other tools will be helpful.
 Probably even in form of guideline, not a rule.


This is quite overengineering to put such in the spec.

 coverity_warnings

should do fine (i.e. prefix with your tool name). It's not any harder than 
coming up with names for your third party library.
Jan 21 2014
parent reply "Brian Schott" <briancschott gmail.com> writes:
On Tuesday, 21 January 2014 at 20:26:57 UTC, Walter Bright wrote:

 On 1/21/2014 1:33 AM, Dicebot wrote:

 See "reserved namespace" reference. It does not need any 
 special support from
 the language itself but some support from spec that will 
 ensure that those
 attributes won't conflict with user code and other tools will 
 be helpful.
 Probably even in form of guideline, not a rule.


 This is quite overengineering to put such in the spec.

  coverity_warnings

 should do fine (i.e. prefix with your tool name). It's not any 
 harder than coming up with names for your third party library.


"test.d(10): Error: undefined identifier coverity_warnings"

In order for this to work the analysis tool would have to 
distribute a .d or .di file that is imported by any module that 
needs to suppress warnings. Java has the SuppressWarnings 
annotation in the standard java.lang to avoid this.
Jan 21 2014
next sibling parent Walter Bright <newshound2 digitalmars.com> writes:
On 1/21/2014 1:07 PM, Brian Schott wrote:

 On Tuesday, 21 January 2014 at 20:26:57 UTC, Walter Bright wrote:

  coverity_warnings

 should do fine (i.e. prefix with your tool name). It's not any harder than
 coming up with names for your third party library.


 "test.d(10): Error: undefined identifier coverity_warnings"

 In order for this to work the analysis tool would have to distribute a .d or
.di
 file that is imported by any module that needs to suppress warnings. Java has
 the SuppressWarnings annotation in the standard java.lang to avoid this.


The trouble is if you start doing that, you end up in an endless ratrace of 
adding ever more "standard" names.

If you're going to use a static checker, it doesn't seem to me to be a big 
burden to provide an import for it.
Jan 21 2014
prev sibling parent Jacob Carlborg <doob me.com> writes:
On 2014-01-21 22:07, Brian Schott wrote:


 "test.d(10): Error: undefined identifier coverity_warnings"

 In order for this to work the analysis tool would have to distribute a
 .d or .di file that is imported by any module that needs to suppress
 warnings. Java has the SuppressWarnings annotation in the standard
 java.lang to avoid this.


Or just use an ugly string:

 ("coverity_warnings")

-- 
/Jacob Carlborg
Jan 22 2014
prev sibling next sibling parent Walter Bright <newshound2 digitalmars.com> writes:
On 1/20/2014 8:34 PM, Brian Schott wrote:

 I've checked in code to the DScanner project that gives it some basic static
 analysis capabilities. When run with the --styleCheck option, it will warn
about
 a few things like empty declarations, implicit string concatenation, classes
 with lowercase_names, catching "Exception", and a few other things.

 There's a small feature wishlist in the project's README, but I'd like to get
 some opinions from the newsgroup: What kinds of errors have you seen in your
 code that you think a static analysis tool could help with?


Sooner or later, you're going to want to add data flow analysis. DFA will open 
up a universe of useful checks it can do. For example, you can do things like:

class C { int x; }
C foo() { return null; }
int bar(int i) {
     auto c = i ? foo() : new C();
     return c.x;        // error, path to null dereference
}

and a heckuva lot more.

For a laundry list, google Coverity and look at the bug reports it generates. 
Many of the reports have no meaning for D, as D has defined them out of 
existence, but there are plenty of others.
Jan 21 2014
prev sibling next sibling parent Jacob Carlborg <doob me.com> writes:
On 2014-01-21 05:34, Brian Schott wrote:

 I've checked in code to the DScanner project that gives it some basic
 static analysis capabilities. When run with the --styleCheck option, it
 will warn about a few things like empty declarations, implicit string
 concatenation, classes with lowercase_names, catching "Exception", and a
 few other things.

 There's a small feature wishlist in the project's README, but I'd like
 to get some opinions from the newsgroup: What kinds of errors have you
 seen in your code that you think a static analysis tool could help with?


Have a look at the Clang static analyzer as well. How accurate source 
information is kept? Xcode can, with the help of Clang, graphically show 
the flow path.

-- 
/Jacob Carlborg
Jan 21 2014
prev sibling next sibling parent Walter Bright <newshound2 digitalmars.com> writes:
On 1/20/2014 8:34 PM, Brian Schott wrote:

 There's a small feature wishlist in the project's README, but I'd like to get
 some opinions from the newsgroup: What kinds of errors have you seen in your
 code that you think a static analysis tool could help with?


Here's a great source of potential rules to add:

http://www.stroustrup.com/JSF-AV-rules.pdf
Jan 23 2014
prev sibling next sibling parent "Brian Schott" <briancschott gmail.com> writes:
I just added two new rules, a check for if/else blocks that are 
identical and a check for assign expressions where the left and 
right side of the '=' operator are the same.

It found two bugs in Phobos:

https://issues.dlang.org/show_bug.cgi?id=12609
https://issues.dlang.org/show_bug.cgi?id=12608
Apr 21 2014
prev sibling next sibling parent "Kagamin" <spam here.lot> writes:
Implicit conversion long - size_t - int.
Null dereference can sometimes be detected statically, e.g. when 
the variable is not initialized.
Possible null dereference after downcast, though this one can be 
annoying.

I suggest to configure warnings with a config file, as the 
configuration can be big depending on the project code style. 
Another possibility is optional pragmas for really evil local 
overrides - resharper style comments - not only analysis tools 
can benefit from them.
Apr 22 2014
prev sibling next sibling parent "Kagamin" <spam here.lot> writes:
Also escape analysis.

Bug found by frama-c:
http://blog.frama-c.com/index.php?post/2014/02/23/CVE-2013-5914
Quote: "Allow me to put it this way: if the Apple SSL bug is a 
coup from the NSA, then you US citizens are lucky. Our spy agency 
in Europe is so much better that it does not even have a name you 
have heard before, and it is able to plant bugs where the buffer 
overflow leading to arbitrary code execution is three function 
calls away from the actual bug. The bug from our spy agency is so 
deniable that the code actually used to be fine when there were 
only two minor revisions of the SSL protocol. The backdoors from 
your spy agency are so lame that the Internet has opinions about 
them."
Apr 22 2014
prev sibling parent reply Marco Leise <Marco.Leise gmx.de> writes:
Am Tue, 21 Jan 2014 04:34:56 +0000
schrieb "Brian Schott" <briancschott gmail.com>:


 There's a small feature wishlist in the project's README, but I'd=20
 like to get some opinions from the newsgroup: What kinds of=20
 errors have you seen in your code that you think a static=20
 analysis tool could help with?


Yes, this one:

size_t shiftAmount =3D 63;
[=E2=80=A6]
auto x =3D 1 << shiftAmount;

The trouble is that auto will now resolve to int instead of
size_t as indicated by the type of shiftAmount. Sure, my fault
was to use an innocent =C2=BB1=C2=AB instead of =C2=BBcast(size_t) 1=C2=AB.=
 So the
result is:

int x =3D -2147483648;

But =C2=BB1 << size_t=C2=AB doesn't always yield an int result! Compare to
this:

size_t x =3D 1 << shiftAmount;

which becomes:

size_t x =3D 18446744071562067968;


Two possible warnings could be:
- Shifting an =C2=BBint=C2=AB by a =C2=BBsize_t=C2=AB is not the correct wa=
y to
  enforce a =C2=BBsize_t=C2=AB result. Please use
  =C2=BBcast(size_t) 1 << shiftAmount=C2=AB if that was the intention.
- =C2=BBauto=C2=AB variable definition will resolve to =C2=BBint=C2=AB and =
may
  lose information from expression =C2=BB1 << shiftAmount=C2=AB. Please
  replace =C2=BBauto=C2=AB with =C2=BBint=C2=AB if that is what you want or=
 set
  the correct data type otherwise.

In both cases an explicit mention of a data type resolves the
ambiguity.

--=20
Marco
Apr 23 2014
next sibling parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Wed, 23 Apr 2014 22:56:54 -0400, Marco Leise <Marco.Leise gmx.de> wro=
te:


 Am Tue, 21 Jan 2014 04:34:56 +0000
 schrieb "Brian Schott" <briancschott gmail.com>:


 There's a small feature wishlist in the project's README, but I'd
 like to get some opinions from the newsgroup: What kinds of
 errors have you seen in your code that you think a static
 analysis tool could help with?


 Yes, this one:

 size_t shiftAmount =3D 63;
 [=E2=80=A6]
 auto x =3D 1 << shiftAmount;

 The trouble is that auto will now resolve to int instead of
 size_t as indicated by the type of shiftAmount. Sure, my fault
 was to use an innocent =C2=BB1=C2=AB instead of =C2=BBcast(size_t) 1=C2=


=AB.

You could use 1UL instead.

-Steve
Apr 23 2014
parent reply Marco Leise <Marco.Leise gmx.de> writes:
Am Wed, 23 Apr 2014 22:56:27 -0400
schrieb "Steven Schveighoffer" <schveiguy yahoo.com>:


 On Wed, 23 Apr 2014 22:56:54 -0400, Marco Leise <Marco.Leise gmx.de> wrot=


e:

=20

 Am Tue, 21 Jan 2014 04:34:56 +0000
 schrieb "Brian Schott" <briancschott gmail.com>:


 There's a small feature wishlist in the project's README, but I'd
 like to get some opinions from the newsgroup: What kinds of
 errors have you seen in your code that you think a static
 analysis tool could help with?


 Yes, this one:

 size_t shiftAmount =3D 63;
 [=E2=80=A6]
 auto x =3D 1 << shiftAmount;

 The trouble is that auto will now resolve to int instead of
 size_t as indicated by the type of shiftAmount. Sure, my fault
 was to use an innocent =C2=BB1=C2=AB instead of =C2=BBcast(size_t) 1=C2=




=AB.

=20
 You could use 1UL instead.
=20
 -Steve


No, that would give you a ulong result.

--=20
Marco
Apr 23 2014
parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Wed, 23 Apr 2014 23:15:01 -0400, Marco Leise <Marco.Leise gmx.de> wro=
te:


 Am Wed, 23 Apr 2014 22:56:27 -0400
 schrieb "Steven Schveighoffer" <schveiguy yahoo.com>:


 On Wed, 23 Apr 2014 22:56:54 -0400, Marco Leise <Marco.Leise gmx.de> =




 =


 wrote:


 Am Tue, 21 Jan 2014 04:34:56 +0000
 schrieb "Brian Schott" <briancschott gmail.com>:


 There's a small feature wishlist in the project's README, but I'd
 like to get some opinions from the newsgroup: What kinds of
 errors have you seen in your code that you think a static
 analysis tool could help with?


 Yes, this one:

 size_t shiftAmount =3D 63;
 [=E2=80=A6]
 auto x =3D 1 << shiftAmount;

 The trouble is that auto will now resolve to int instead of
 size_t as indicated by the type of shiftAmount. Sure, my fault
 was to use an innocent =C2=BB1=C2=AB instead of =C2=BBcast(size_t) =






1=C2=AB.

 You could use 1UL instead.

 -Steve


 No, that would give you a ulong result.


Hm... I was thinking in terms of 1 << 63, that must be a ulong, no?

But I see your point that size_t may be 32 bits.

I also think this will work:

size_t(1);

-Steve
Apr 24 2014
parent reply Marco Leise <Marco.Leise gmx.de> writes:
Am Thu, 24 Apr 2014 10:26:48 -0400
schrieb "Steven Schveighoffer" <schveiguy yahoo.com>:


 On Wed, 23 Apr 2014 23:15:01 -0400, Marco Leise <Marco.Leise gmx.de> wrot=


e:

=20

 Am Wed, 23 Apr 2014 22:56:27 -0400
 schrieb "Steven Schveighoffer" <schveiguy yahoo.com>:


 On Wed, 23 Apr 2014 22:56:54 -0400, Marco Leise <Marco.Leise gmx.de> =






=20

 wrote:


 Am Tue, 21 Jan 2014 04:34:56 +0000
 schrieb "Brian Schott" <briancschott gmail.com>:


 There's a small feature wishlist in the project's README, but I'd
 like to get some opinions from the newsgroup: What kinds of
 errors have you seen in your code that you think a static
 analysis tool could help with?


 Yes, this one:

 size_t shiftAmount =3D 63;
 [=E2=80=A6]
 auto x =3D 1 << shiftAmount;

 The trouble is that auto will now resolve to int instead of
 size_t as indicated by the type of shiftAmount. Sure, my fault
 was to use an innocent =C2=BB1=C2=AB instead of =C2=BBcast(size_t) 1=








=C2=AB.

 You could use 1UL instead.

 -Steve


 No, that would give you a ulong result.


=20
 Hm... I was thinking in terms of 1 << 63, that must be a ulong, no?


Actually in _that_ case the compiler will yell at you that the
valid range to shift an =C2=BBint=C2=AB is [0..31].


 But I see your point that size_t may be 32 bits.

 I also think this will work:
=20
 size_t(1);
=20
 -Steve


Both you and Artur mentioned it. Will this generalized ctor
syntax be in 2.066 ? It looks much less like "code smell" when
you don't have to use a cast any more even if it is just a
rewrite.

--=20
Marco
Apr 24 2014
parent "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Thu, 24 Apr 2014 15:40:23 -0400, Marco Leise <Marco.Leise gmx.de> wro=
te:


 Am Thu, 24 Apr 2014 10:26:48 -0400
 schrieb "Steven Schveighoffer" <schveiguy yahoo.com>:


 On Wed, 23 Apr 2014 23:15:01 -0400, Marco Leise <Marco.Leise gmx.de> =




 =


 wrote:


 Am Wed, 23 Apr 2014 22:56:27 -0400
 schrieb "Steven Schveighoffer" <schveiguy yahoo.com>:


 On Wed, 23 Apr 2014 22:56:54 -0400, Marco Leise <Marco.Leise gmx.d=








e>

 wrote:


 Am Tue, 21 Jan 2014 04:34:56 +0000
 schrieb "Brian Schott" <briancschott gmail.com>:


 There's a small feature wishlist in the project's README, but I=












'd

 like to get some opinions from the newsgroup: What kinds of
 errors have you seen in your code that you think a static
 analysis tool could help with?


 Yes, this one:

 size_t shiftAmount =3D 63;
 [=E2=80=A6]
 auto x =3D 1 << shiftAmount;

 The trouble is that auto will now resolve to int instead of
 size_t as indicated by the type of shiftAmount. Sure, my fault
 was to use an innocent =C2=BB1=C2=AB instead of =C2=BBcast(size_=










t) 1=C2=AB.

 You could use 1UL instead.

 -Steve


 No, that would give you a ulong result.


 Hm... I was thinking in terms of 1 << 63, that must be a ulong, no?


 Actually in _that_ case the compiler will yell at you that the
 valid range to shift an =C2=BBint=C2=AB is [0..31].


*sigh* The compiler is too smart for it's own good ;)

This SHOULD compile and result in a long. I can't see how you would have=
  =

meant anything else, and range propagation should work for a literal.


 But I see your point that size_t may be 32 bits.

 I also think this will work:

 size_t(1);

 -Steve


 Both you and Artur mentioned it. Will this generalized ctor
 syntax be in 2.066 ?


I don't know. I thought it was in 2.065, but see that it's not. I have  =

read that it was introduced somewhere, so I assumed it was already in.  =

Maybe only in git HEAD.


 It looks much less like "code smell" when
 you don't have to use a cast any more even if it is just a
 rewrite.


Yeah definitely. Cast should not be required for such mundane and  =

obviously safe things.

-Steve
Apr 24 2014
prev sibling parent reply Artur Skawina via Digitalmars-d <digitalmars-d puremagic.com> writes:
On 04/24/14 04:56, Marco Leise via Digitalmars-d wrote:

 But »1 << size_t« doesn't always yield an int result! Compare to


It does. That expression *always* yields an int [1]. Assigning the
result to a wider type does not affect the value (the overflow has
already happened by then).


 size_t x = 1 << shiftAmount;


This would almost certainly be a bug, if shiftAmount could ever
become greater than 30. The `size_t = 1<<31` case is also very
unlikely to do what the programmer intended.


 - »auto« variable definition will resolve to »int« and may
   lose information from expression »1 << shiftAmount«. Please
   replace »auto« with »int« if that is what you want or set
   the correct data type otherwise.


`size_t x = 1 << shiftAmount` is definitely not something that
should be recommended, see above. Just use the correct type on
the lhs of shift operators.

artur

[1] there could be an exception for certain compile-time contexts,
    but I don't think that would work in D (same code would give
    different results when run at CT and RT).
Apr 24 2014
parent reply Marco Leise <Marco.Leise gmx.de> writes:
Am Thu, 24 Apr 2014 13:11:18 +0200
schrieb Artur Skawina via Digitalmars-d
<digitalmars-d puremagic.com>:


 `size_t x = 1 << shiftAmount` is definitely not something that
 should be recommended, see above. Just use the correct type on
 the lhs of shift operators.


auto x = cast(size_t) 1 << shiftAmount;  // really ?! :(

In that case it is better to define ONE as a constant :)

enum ONE = cast(size_t) 1;
auto x = ONE << shiftAmount;

-- 
Marco
Apr 24 2014
parent Artur Skawina via Digitalmars-d <digitalmars-d puremagic.com> writes:
On 04/24/14 14:49, Marco Leise via Digitalmars-d wrote:

 Am Thu, 24 Apr 2014 13:11:18 +0200
 schrieb Artur Skawina via Digitalmars-d
 <digitalmars-d puremagic.com>:
 

 `size_t x = 1 << shiftAmount` is definitely not something that
 should be recommended, see above. Just use the correct type on
 the lhs of shift operators.


 
 auto x = cast(size_t) 1 << shiftAmount;  // really ?! :(


Yes. D has not improved the situation in this area; it's no
different from C.

A new enough compiler could make it look slightly better:

    auto x = size_t(1) << shiftAmount;


Of course the more fundamental problem is that 'size_t' is just
an alias and not a distinct type in D.

artur
Apr 24 2014