[Issue 4397] New: D1 const does not work

http://d.puremagic.com/issues/show_bug.cgi?id=4397

           Summary: D1 const does not work
           Product: D
           Version: D1 & D2
          Platform: Other
        OS/Version: All
            Status: NEW
          Keywords: wrong-code
          Severity: regression
          Priority: P1
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: nfxjfg@gmail.com


--- Comment #0 from nfxjfg@gmail.com 2010-06-27 10:30:32 PDT ---
In the following example, foo() will create an array literal on each call, instead of returning a statically shared / compile time value. On D2, the same may happen when using enum instead of const (I didn't test it).

In many cases, this codegen bug may go unnoticed, which makes it just worse.

$ cat rtz.d
struct X {
    int[] a;
}

const cX = X([1,2]);

X foo() {
    return cX;
}

$ dmd -c rtz.d
$ objdump -d -Mintel rtz.o -r
...
00000000 <_D3rtz3fooFZS3rtz1X>:
   0:   55                      push   ebp
   1:   8b ec                   mov    ebp,esp
   3:   83 ec 08                sub    esp,0x8
   6:   53                      push   ebx
   7:   6a 02                   push   0x2
   9:   6a 01                   push   0x1
   b:   6a 02                   push   0x2
   d:   b8 00 00 00 00          mov    eax,0x0
                        e: R_386_32     _D11TypeInfo_Ai6__initZ
  12:   50                      push   eax
  13:   e8 fc ff ff ff          call   14 <_D3rtz3fooFZS3rtz1X+0x14>
                        14: R_386_PC32  _d_arrayliteralT
  18:   89 c1                   mov    ecx,eax
  1a:   bb 02 00 00 00          mov    ebx,0x2
  1f:   89 5d f8                mov    DWORD PTR [ebp-0x8],ebx
  22:   89 4d fc                mov    DWORD PTR [ebp-0x4],ecx
  25:   8b 55 fc                mov    edx,DWORD PTR [ebp-0x4]
  28:   8b 45 f8                mov    eax,DWORD PTR [ebp-0x8]
  2b:   83 c4 10                add    esp,0x10
  2e:   5b                      pop    ebx
  2f:   c9                      leave
  30:   c3                      ret

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http://d.puremagic.com/issues/show_bug.cgi?id=4397 nfxjfg@gmail.com changed: What |Removed |Added ---------------------------------------------------------------------------- Summary|D1 const does not work |D1 const/CTFE does not work --- Comment #1 from nfxjfg@gmail.com 2010-07-11 22:02:35 PDT --- Does anyone know a workaround for this? It's starting to get annoying, and Walter probably died, so it will take a while until this is fixed. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=4397 nfxjfg@gmail.com changed: What |Removed |Added ---------------------------------------------------------------------------- Summary|D1 const/CTFE does not work |const/CTFE does not work --- Comment #2 from nfxjfg@gmail.com 2010-07-11 22:04:16 PDT --- (Wrong code on v2.046 too, when switching const with enum.) -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=4397 --- Comment #4 from Sobirari Muhomori <dfj1esp02@sneakemail.com> 2010-07-28 12:04:59 PDT --- Shouldn't literals be immutable and the code - invalid? -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=4397 --- Comment #5 from Don <clugdbug@yahoo.com.au> 2010-07-28 12:29:57 PDT --- (In reply to comment #4) > Shouldn't literals be immutable and the code - invalid? I think they *should*. I argued strongly for immutable array literals. But I lost. So the code is valid, but likely to be very slow for a very long time. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=4397 --- Comment #6 from nfxjfg@gmail.com 2010-07-28 13:05:25 PDT --- It's not valid. This is a systems programming language, and the compiler can't just randomly insert memory allocations. What if you wrote a kernel in D? I insist on the wrong-code keyword. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=4397 --- Comment #7 from nfxjfg@gmail.com 2010-07-28 13:06:29 PDT --- >and the compiler can't just randomly insert memory allocations. Add "that are not supposed to be there". -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=4397 --- Comment #8 from Sobirari Muhomori <dfj1esp02@sneakemail.com> 2010-07-28 19:57:40 PDT --- Well... there can be a problem with immutable literals because immutability is transitive... hmm... Even if literals aren't immutable, compiler can still catch assignment of literal to mutable array and report error. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=4397 Don <clugdbug@yahoo.com.au> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords|wrong-code |performance --- Comment #9 from Don <clugdbug@yahoo.com.au> 2010-07-28 23:01:36 PDT --- (In reply to comment #8) > Well... there can be a problem with immutable literals because immutability is > transitive... hmm... > Even if literals aren't immutable, compiler can still catch assignment of > literal to mutable array and report error. But it is EXPLICITLY LEGAL to assign a literal to a mutable array. There is an invisible dup by design. I don't like this, I argued strongly against it, but it's in there. This isn't wrong code. (Similarly, you can write const C x = new C; The C will be allocated on the heap, even though it will never change afterwards). -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

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