Re: CTFE bug or enhancement?
On Thu, Jul 03, 2014 at 02:09:09AM +, safety0ff via Digitalmars-d-learn wrote: On Thursday, 3 July 2014 at 02:02:19 UTC, safety0ff wrote: On Thursday, 3 July 2014 at 01:55:14 UTC, safety0ff wrote: Actually, this is an enhancement because adding: enum b = blah Makes them fail. :( The question is now: how can the delegate be evaluated for the return value but not for the enum? Looks like an ICE: https://github.com/D-Programming-Language/dmd/blob/master/src/interpret.c#L5169 All ICE's are bugs and should be reported as such. T -- If the comments and the code disagree, it's likely that *both* are wrong. -- Christopher
Re: CTFE bug or enhancement?
Actually, this is an enhancement because adding: enum b = blah Makes them fail. :(
Re: CTFE bug or enhancement?
On Thursday, 3 July 2014 at 01:55:14 UTC, safety0ff wrote: Actually, this is an enhancement because adding: enum b = blah Makes them fail. :( The question is now: how can the delegate be evaluated for the return value but not for the enum?
Re: CTFE bug or enhancement?
On Thursday, 3 July 2014 at 02:02:19 UTC, safety0ff wrote: On Thursday, 3 July 2014 at 01:55:14 UTC, safety0ff wrote: Actually, this is an enhancement because adding: enum b = blah Makes them fail. :( The question is now: how can the delegate be evaluated for the return value but not for the enum? Looks like an ICE: https://github.com/D-Programming-Language/dmd/blob/master/src/interpret.c#L5169
Re: ctfe bug?
Johannes Pfau wrote: Has this bug already been filed? I could possibly circumvent it by making ragel use array indexing instead of pointers, but that'd be a performance issue for runtime code as well. OK, I found a workaround: If I use data[x] = parse!ubyte(input[p-input.ptr-2 .. p-input.ptr], 16); instead, it works. So the issue is related to pointer slicing in ctfe.
Re: ctfe bug?
On 2011-12-22 08:47, Johannes Pfau wrote:
Hi,
the following code is reduced from a parser generated with Ragel
(http://www.complang.org/ragel/). That's also the reason why it's
using pointers instead of array access, but Ragel guarantees that there
won't be any out-of-bound reads.
AFAIK pointers are supported in CTFE now as long as they're pointing to an
array and there are no out-of-bounds reads. Still, the following code fails:
ubyte[4] testCTFE()
{
ubyte[4] data;
string input = 8ab3060e2cba4f23b74cb52db3bdfb46;
auto p = input.ptr;
p++; p++;
data[0] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[1] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[2] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[3] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
return data;
}
enum ctfe = testCTFE();
void main()
{
import std.stdio;
writeln(testCTFE()); //[138, 179, 6, 14]
writeln(ctfe); //[138, 138, 138, 138]
}
Has this bug already been filed? I could possibly circumvent it by making
ragel use array indexing instead of pointers, but that'd be a performance
issue for runtime code as well.
Why would arrays be slower than pointers? You do know that you can turn
off array bounds checking?
--
/Jacob Carlborg
Re: ctfe bug?
Jacob Carlborg wrote:
On 2011-12-22 08:47, Johannes Pfau wrote:
Hi,
the following code is reduced from a parser generated with Ragel
(http://www.complang.org/ragel/). That's also the reason why it's
using pointers instead of array access, but Ragel guarantees that there
won't be any out-of-bound reads.
AFAIK pointers are supported in CTFE now as long as they're pointing to
an array and there are no out-of-bounds reads. Still, the following code
fails:
ubyte[4] testCTFE()
{
ubyte[4] data;
string input = 8ab3060e2cba4f23b74cb52db3bdfb46;
auto p = input.ptr;
p++; p++;
data[0] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[1] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[2] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[3] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
return data;
}
enum ctfe = testCTFE();
void main()
{
import std.stdio;
writeln(testCTFE()); //[138, 179, 6, 14]
writeln(ctfe); //[138, 138, 138, 138]
}
Has this bug already been filed? I could possibly circumvent it by making
ragel use array indexing instead of pointers, but that'd be a performance
issue for runtime code as well.
Why would arrays be slower than pointers? You do know that you can turn
off array bounds checking?
Don't know, but I remember some benchmarks showed that arrays were slower,
even with bounds-checking off. (I think that was brought up in some
discussion about the tango xml parser).
Also the default for ragel is to use pointers, so I'd like to use that.
Making it use arrays means extra work ;-)
And turning off bounds-checking is not a perfect solution, as it applies to
the complete module. As I said, ragel makes sure that the pointer access is
safe, so there's really no issue in using pointers.
Re: ctfe bug?
On 12/22/2011 10:28 AM, Jacob Carlborg wrote:
On 2011-12-22 08:47, Johannes Pfau wrote:
Hi,
the following code is reduced from a parser generated with Ragel
(http://www.complang.org/ragel/). That's also the reason why it's
using pointers instead of array access, but Ragel guarantees that there
won't be any out-of-bound reads.
AFAIK pointers are supported in CTFE now as long as they're pointing
to an
array and there are no out-of-bounds reads. Still, the following code
fails:
ubyte[4] testCTFE()
{
ubyte[4] data;
string input = 8ab3060e2cba4f23b74cb52db3bdfb46;
auto p = input.ptr;
p++; p++;
data[0] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[1] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[2] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[3] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
return data;
}
enum ctfe = testCTFE();
void main()
{
import std.stdio;
writeln(testCTFE()); //[138, 179, 6, 14]
writeln(ctfe); //[138, 138, 138, 138]
}
Has this bug already been filed? I could possibly circumvent it by making
ragel use array indexing instead of pointers, but that'd be a performance
issue for runtime code as well.
Why would arrays be slower than pointers? You do know that you can turn
off array bounds checking?
Yes but the length has to be stored and updated, therefore for example
p++ is less machine instructions/memory accesses/register pressure than
arr = arr[1..$].
Re: ctfe bug?
On 2011-12-22 14:39, Timon Gehr wrote:
On 12/22/2011 10:28 AM, Jacob Carlborg wrote:
On 2011-12-22 08:47, Johannes Pfau wrote:
Hi,
the following code is reduced from a parser generated with Ragel
(http://www.complang.org/ragel/). That's also the reason why it's
using pointers instead of array access, but Ragel guarantees that there
won't be any out-of-bound reads.
AFAIK pointers are supported in CTFE now as long as they're pointing
to an
array and there are no out-of-bounds reads. Still, the following code
fails:
ubyte[4] testCTFE()
{
ubyte[4] data;
string input = 8ab3060e2cba4f23b74cb52db3bdfb46;
auto p = input.ptr;
p++; p++;
data[0] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[1] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[2] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[3] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
return data;
}
enum ctfe = testCTFE();
void main()
{
import std.stdio;
writeln(testCTFE()); //[138, 179, 6, 14]
writeln(ctfe); //[138, 138, 138, 138]
}
Has this bug already been filed? I could possibly circumvent it by
making
ragel use array indexing instead of pointers, but that'd be a
performance
issue for runtime code as well.
Why would arrays be slower than pointers? You do know that you can turn
off array bounds checking?
Yes but the length has to be stored and updated, therefore for example
p++ is less machine instructions/memory accesses/register pressure than
arr = arr[1..$].
Ok, I see. Then this seems to be a very performance critical piece of code.
--
/Jacob Carlborg
Re: ctfe bug?
Jacob Carlborg wrote:
On 2011-12-22 14:39, Timon Gehr wrote:
On 12/22/2011 10:28 AM, Jacob Carlborg wrote:
On 2011-12-22 08:47, Johannes Pfau wrote:
Hi,
the following code is reduced from a parser generated with Ragel
(http://www.complang.org/ragel/). That's also the reason why it's
using pointers instead of array access, but Ragel guarantees that there
won't be any out-of-bound reads.
AFAIK pointers are supported in CTFE now as long as they're pointing
to an
array and there are no out-of-bounds reads. Still, the following code
fails:
ubyte[4] testCTFE()
{
ubyte[4] data;
string input = 8ab3060e2cba4f23b74cb52db3bdfb46;
auto p = input.ptr;
p++; p++;
data[0] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[1] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[2] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
data[3] = parse!ubyte((p-2)[0 .. 2], 16);
p++; p++;
return data;
}
enum ctfe = testCTFE();
void main()
{
import std.stdio;
writeln(testCTFE()); //[138, 179, 6, 14]
writeln(ctfe); //[138, 138, 138, 138]
}
Has this bug already been filed? I could possibly circumvent it by
making
ragel use array indexing instead of pointers, but that'd be a
performance
issue for runtime code as well.
Why would arrays be slower than pointers? You do know that you can turn
off array bounds checking?
Yes but the length has to be stored and updated, therefore for example
p++ is less machine instructions/memory accesses/register pressure than
arr = arr[1..$].
Ok, I see. Then this seems to be a very performance critical piece of
code.
In this special case it's not that important (simple UUID parser), but ragel
is also used for HTTP parsers in webservers (lighttpd2), json parsers, etc
and it's main advantage is speed.
