• d-bugmail puremagic.com Mar 14 2006
• Thomas Kuehne <thomas-dloop kuehne.cn> Mar 18 2006
• d-bugmail puremagic.com Mar 19 2006
• Thomas Kuehne <thomas-dloop kuehne.cn> Jul 12 2006

d-bugmail puremagic.com writes:

http://d.puremagic.com/bugzilla/show_bug.cgi?id=51

           Summary: String cast overrides the char type of decorated string
                    literals.
           Product: D
           Version: 0.149
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Severity: minor
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: daiphoenix lycos.com


Observe the following code:

  char[6] cstr = "123456"c;
  auto str1 = cast(wchar[3])(cstr);
  auto str2 = cast(wchar[3])("123456"c);

  writefln("str1: ", (cast(char[])str1).length , " : ", (cast(char[])str1));
  // prints: str1: 6 : 123456
  writefln("str2: ", (cast(char[])str2).length , " : ", (cast(char[])str2)); 
  // prints: str2: 6 : ?1?2?3

One would expect the same behaviour from str1 and str2, however the
cast(wchar[3]) in str2 overrides the string decorator 'c', and makes the string
literal "123456" (i.e. the string "instance" data) be of type wchar[6] instead
of char[6].


-- 

Thomas Kuehne <thomas-dloop kuehne.cn> writes:

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

d-bugmail puremagic.com schrieb am 2006-03-14:
 Observe the following code:

   char[6] cstr = "123456"c;
   auto str1 = cast(wchar[3])(cstr);
   auto str2 = cast(wchar[3])("123456"c);

   writefln("str1: ", (cast(char[])str1).length , " : ", (cast(char[])str1));
   // prints: str1: 6 : 123456
   writefln("str2: ", (cast(char[])str2).length , " : ", (cast(char[])str2)); 
   // prints: str2: 6 : ?1?2?3

 One would expect the same behaviour from str1 and str2, however the
 cast(wchar[3]) in str2 overrides the string decorator 'c', and makes the string
 literal "123456" (i.e. the string "instance" data) be of type wchar[6] instead
 of char[6].


This might seem confusing, but is the correct behaviour.
http://www.digitalmars.com/d/arrays.html

# The type of a string is determined by the semantic phase of
# compilation. The type is one of: char[], wchar[], dchar[], and is
# determined by implicit conversion rules. If there are two equally
# applicable implicit conversions, the result is an error. To
# disambiguate these cases, a cast is appropriate:
#
# cast(wchar [])"abc"	// this is an array of wchar characters

Thomas


-----BEGIN PGP SIGNATURE-----

iD8DBQFEHRi13w+/yD4P9tIRAmgpAJ9F/KNd1JSBTBOp1QME7RA6Lwja9wCfT7Gx
SlkT9jiEQ1rxtIl/cc7wT7s=
=aqz7
-----END PGP SIGNATURE-----

d-bugmail puremagic.com writes:

http://d.puremagic.com/bugzilla/show_bug.cgi?id=51





------- Comment #2 from daiphoenix lycos.com  2006-03-19 04:30 -------
(In reply to comment #1)
 -----BEGIN PGP SIGNED MESSAGE-----
 Hash: SHA1
 This might seem confusing, but is the correct behaviour.
 http://www.digitalmars.com/d/arrays.html
 # The type of a string is determined by the semantic phase of
 # compilation. The type is one of: char[], wchar[], dchar[], and is
 # determined by implicit conversion rules. If there are two equally
 # applicable implicit conversions, the result is an error. To
 # disambiguate these cases, a cast is appropriate:
 #
 # cast(wchar [])"abc"   // this is an array of wchar characters
 Thomas
 -----BEGIN PGP SIGNATURE-----
 iD8DBQFEHRi13w+/yD4P9tIRAmgpAJ9F/KNd1JSBTBOp1QME7RA6Lwja9wCfT7Gx
 SlkT9jiEQ1rxtIl/cc7wT7s=
 =aqz7
 -----END PGP SIGNATURE-----


That behaviour is true for undecorated string literals, however for decorated
string literals (i.e. those with postfix 'c', 'd', or 'w') it is not so. In
http://www.digitalmars.com/d/lex.html#stringliteral it is said: "The optional
Postfix character gives a specific type to the string, rather than it being
inferred from the context. ..."
Thus postfix-decorated string literals should not be vulnerable to type change
due to casts or other context influences, no?


-- 

Thomas Kuehne <thomas-dloop kuehne.cn> writes:

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

d-bugmail puremagic.com schrieb am 2006-03-14:
 http://d.puremagic.com/bugzilla/show_bug.cgi?id=51


 Observe the following code:

   char[6] cstr = "123456"c;
   auto str1 = cast(wchar[3])(cstr);
   auto str2 = cast(wchar[3])("123456"c);

   writefln("str1: ", (cast(char[])str1).length , " : ", (cast(char[])str1));
   // prints: str1: 6 : 123456
   writefln("str2: ", (cast(char[])str2).length , " : ", (cast(char[])str2)); 
   // prints: str2: 6 : ?1?2?3

 One would expect the same behaviour from str1 and str2, however the
 cast(wchar[3]) in str2 overrides the string decorator 'c', and makes the string
 literal "123456" (i.e. the string "instance" data) be of type wchar[6] instead
 of char[6].


Added to DStress as
http://dstress.kuehne.cn/run/s/string_postfix_07_A.d
http://dstress.kuehne.cn/run/s/string_postfix_07_B.d

Thomas


-----BEGIN PGP SIGNATURE-----

iD8DBQFEtOHcLK5blCcjpWoRAgakAKCOhY7VG1AkTF8IFOz1Ur067Dk+dQCeIlbj
h9EvDdFmTjEL3U2/pdpgnqk=
=rrCR
-----END PGP SIGNATURE-----