• Oleg B (25/25) Nov 22 2017 Hello. I try compile simple example:
• Adam D. Ruppe (5/6) Nov 22 2017 -noboundscheck is extremely harmful. If -betterC implied that, it
• Joakim (8/33) Nov 22 2017 betterC is a new feature that's still being worked on and still
• Nicholas Wilson (3/12) Nov 22 2017 see also https://github.com/ldc-developers/ldc/pull/2426 (also
• codephantom (6/10) Nov 23 2017 Interestingly, ldc2 will compile this ok, without the
• Basile B. (4/16) Nov 23 2017 It's b/c LDC2 doesn't have the most recent betterC features. It
• codephantom (5/25) Nov 23 2017 Thanks. I didn't take that into account (was using LDC 1.5.0
• Michael V. Franklin (2/20) Nov 24 2017 Bug submitted here: https://issues.dlang.org/show_bug.cgi?id=18010

Oleg B <code.viator gmail.com> writes:

Hello. I try compile simple example:

import core.stdc.stdio;
import std.algorithm : min;

extern (C) void main()
{
     char[256] buf;
     buf[] = '\0';

     auto str = "hello world";
     auto ln = min(buf.length, str.length);
     buf[0..ln] = str[0..ln];
     printf("%s\n", buf.ptr);
}

rdmd -betterC bettercarray2.d

and get error:

/tmp/.rdmd-1000/rdmd-bettercarray2.d-435C14EC3DAF09FFABF8ED6919B624C1/o
js/bettercarray2.o: In function `main':
bettercarray2.d:(.text.main[main]+0xbc): undefined reference to 
`_d_arraycopy'
collect2: error: ld returned 1 exit status
Error: linker exited with status 1

If I understand correctly _d_arraycopy is part of druntime and it 
check bounds of array access.

If I add -noboundscheck flag all works fine.

dmd version is 2.076.1

Why -betterC flag not 'include' -noboundscheck flag?
It's bug or in some cases it's useful?

Adam D. Ruppe <destructionator gmail.com> writes:

On Wednesday, 22 November 2017 at 15:10:40 UTC, Oleg B wrote:
 Why -betterC flag not 'include' -noboundscheck flag?

-noboundscheck is extremely harmful. If -betterC implied that, it 
would no longer be a better C, it would just be the same buggy C.

The compiler should perhaps inline the bounds check so it doesn't 
need the druntime function, but it certainly shouldn't skip it.

Joakim <dlang joakim.fea.st> writes:

On Wednesday, 22 November 2017 at 15:10:40 UTC, Oleg B wrote:
 Hello. I try compile simple example:

 import core.stdc.stdio;
 import std.algorithm : min;

 extern (C) void main()
 {
     char[256] buf;
     buf[] = '\0';

     auto str = "hello world";
     auto ln = min(buf.length, str.length);
     buf[0..ln] = str[0..ln];
     printf("%s\n", buf.ptr);
 }

 rdmd -betterC bettercarray2.d

 and get error:

 /tmp/.rdmd-1000/rdmd-bettercarray2.d-435C14EC3DAF09FFABF8ED6919B624C1/o
js/bettercarray2.o: In function `main':
 bettercarray2.d:(.text.main[main]+0xbc): undefined reference to 
 `_d_arraycopy'
 collect2: error: ld returned 1 exit status
 Error: linker exited with status 1

 If I understand correctly _d_arraycopy is part of druntime and 
 it check bounds of array access.

 If I add -noboundscheck flag all works fine.

 dmd version is 2.076.1

 Why -betterC flag not 'include' -noboundscheck flag?
 It's bug or in some cases it's useful?

betterC is a new feature that's still being worked on and still 
has holes in it:

https://github.com/dlang/dmd/pull/7151

I suggest you open an issue for it on bugzilla, as this sounds 
like either a hole or at least something that should be 
documented better:

https://issues.dlang.org

Nicholas Wilson <iamthewilsonator hotmail.com> writes:

On Wednesday, 22 November 2017 at 16:57:10 UTC, Joakim wrote:
 On Wednesday, 22 November 2017 at 15:10:40 UTC, Oleg B wrote:
 [...]

 betterC is a new feature that's still being worked on and still 
 has holes in it:

 https://github.com/dlang/dmd/pull/7151

 I suggest you open an issue for it on bugzilla, as this sounds 
 like either a hole or at least something that should be 
 documented better:

 https://issues.dlang.org

see also https://github.com/ldc-developers/ldc/pull/2426 (also 
WiP).

codephantom <me noyb.com> writes:

On Wednesday, 22 November 2017 at 15:10:40 UTC, Oleg B wrote:
 If I add -noboundscheck flag all works fine.

 dmd version is 2.076.1

 Why -betterC flag not 'include' -noboundscheck flag?
 It's bug or in some cases it's useful?


Interestingly, ldc2 will compile this ok, without the 
-noboundscheck flag

btw. you should start using: boundscheck=off/on/safeonly flag 
instead i believe.

https://dlang.org/dmd-windows.html#switch-boundscheck

Basile B. <b2.temp gmx.com> writes:

On Friday, 24 November 2017 at 00:17:31 UTC, codephantom wrote:
 On Wednesday, 22 November 2017 at 15:10:40 UTC, Oleg B wrote:
 If I add -noboundscheck flag all works fine.

 dmd version is 2.076.1

 Why -betterC flag not 'include' -noboundscheck flag?
 It's bug or in some cases it's useful?


 Interestingly, ldc2 will compile this ok, without the 
 -noboundscheck flag

 btw. you should start using: boundscheck=off/on/safeonly flag 
 instead i believe.

 https://dlang.org/dmd-windows.html#switch-boundscheck

It's b/c LDC2 doesn't have the most recent betterC features. It 
works just like it worked in older DMD release (e.g w 2.075), 
when betterC was "inexact" / "mostly unimplemented"

codephantom <me noyb.com> writes:

On Friday, 24 November 2017 at 05:01:17 UTC, Basile B. wrote:
 On Friday, 24 November 2017 at 00:17:31 UTC, codephantom wrote:
 On Wednesday, 22 November 2017 at 15:10:40 UTC, Oleg B wrote:
 If I add -noboundscheck flag all works fine.

 dmd version is 2.076.1

 Why -betterC flag not 'include' -noboundscheck flag?
 It's bug or in some cases it's useful?


 Interestingly, ldc2 will compile this ok, without the 
 -noboundscheck flag

 btw. you should start using: boundscheck=off/on/safeonly flag 
 instead i believe.

 https://dlang.org/dmd-windows.html#switch-boundscheck

 It's b/c LDC2 doesn't have the most recent betterC features. It 
 works just like it worked in older DMD release (e.g w 2.075), 
 when betterC was "inexact" / "mostly unimplemented"


Thanks. I didn't take that into account (was using LDC 1.5.0 
..based on 2.075.1)

Getting used to monthly compiler updates is a real challenge.. 
not something I'm used to ;-)

Michael V. Franklin <slavo5150 yahoo.com> writes:

On Wednesday, 22 November 2017 at 15:10:40 UTC, Oleg B wrote:

 import core.stdc.stdio;
 import std.algorithm : min;

 extern (C) void main()
 {
     char[256] buf;
     buf[] = '\0';

     auto str = "hello world";
     auto ln = min(buf.length, str.length);
     buf[0..ln] = str[0..ln];
     printf("%s\n", buf.ptr);
 }

 rdmd -betterC bettercarray2.d

 and get error:

 /tmp/.rdmd-1000/rdmd-bettercarray2.d-435C14EC3DAF09FFABF8ED6919B624C1/o
js/bettercarray2.o: In function `main':
 bettercarray2.d:(.text.main[main]+0xbc): undefined reference to 
 `_d_arraycopy'
 collect2: error: ld returned 1 exit status
 Error: linker exited with status 1


Bug submitted here: https://issues.dlang.org/show_bug.cgi?id=18010