[ragel-users] Difference between generated C code using -G0 and -T0

[Adrian Thurston]

Hi Dan,

Thank you for submitting this. It is definitely a bug in the condition 
implementation.

I haven't dug into the details yet, but I can say the difference is 
resolved in ragel 7, which has a completely new implementation of 
conditions in the NFA to DFA algorithm, as well as the code generation step.

Ragel 7 is on the master branch. It is still experimental. Currently 
only the C and D code generators work. Quite a bit has changed. Building 
it requires the the master branch of colm.

I'm not sure if a workaround will be possible for ragel 6.

Thank you for your attention to detail!

Adrian

On 13-11-14 03:29 AM, Daniel Salzman wrote:
> Hi,
>
> I have reduced the problematic code which behaves differently in G mode
> comparing to T or F.
> Please, is there anybody who can fix it?
>
> T: output is "A"
> G: output is "B"
>
> =======================================
> #include <stdio.h>
>
> %%{
> machine foo;
>
> sep = ( [ ]
> | ';' when { 0 }
> )+;
>
> cmt = ^[ ;] >!{ printf("A\n"); } . 'x' >!{ printf("B\n"); };
>
> main := sep . cmt;
> }%%
>
> %% write data;
>
> void main()
> {
> char buffer[] = " ;";
>
> char *p = buffer;
> char *pe = buffer + sizeof(buffer);
> char *eof = pe;
> int cs = foo_start;
>
> %% write exec;
> }
> =======================================
>
> Thanks
>
>
> On 06/25/2013 01:18 PM, Daniel Salzman wrote:
>> Hi,
>>
>> At the beginning I would like to thank you for the great project Ragel.
>> It allows us (www.knot-dns.cz) to have realy fast parser for DNS zone
>> files.
>>
>> But I have recently noticed that there is a small bug in C code
>> generation with G{0,1,2},
>> because there is different behaviour between G and T, F modes.
>>
>> Meaningless and very pruned snippet of code which can demonstrate the
>> problem:
>>
>> == test.rl ==
>> #include <stdlib.h>
>> #include <stdio.h>
>>
>> %%{
>> machine zone_scanner;
>>
>> newline = '\n';
>> comment = ';' . (^newline)*;
>> wchar = [ \t\n;];
>>
>> sep = ( [ \t]
>> | (comment? . newline) when { 0 }
>> )+;
>>
>> err_line := (^newline)* . newline @{ fgoto main; };
>>
>> action _text_char_error {
>> printf("!TXT_ERROR!\n");
>> fhold; fgoto err_line;
>> }
>>
>> text = ^wchar . (alpha $!_text_char_error)+;
>>
>> main := "$INCLUDE" . sep . text . newline;
>> }%%
>>
>> %% write data;
>>
>> int main(int argc, char **argv)
>> {
>> char buffer[4096];
>> FILE* f;
>> long numbytes;
>>
>> f = fopen(argv[1], "r");
>> fseek(f, 0, SEEK_END);
>> numbytes = ftell(f);
>> fseek(f, 0, SEEK_SET);
>> fread(buffer, 1, numbytes, f);
>>
>> char *p = buffer;
>> char *pe = buffer + numbytes;
>> char *eof = pe;
>> int stack[16];
>> int cs = zone_scanner_start;
>> int top;
>>
>> %% write exec;
>>
>> if (cs == zone_scanner_error) {
>> printf("!MISC_ERROR!\n");
>> return -1;
>> }
>>
>> return 0;
>> }
>>
>> == input.txt ==
>> $INCLUDE ; Missing filename
>> ==========
>>
>> ragel -T0 test.rl -o testT.c
>> gcc testT.c -o testT
>> ./testT ./input.txt
>> !MISC_ERROR!
>>
>> ragel -G0 test.rl -o testG.c
>> gcc testG.c -o testG
>> ./testG ./input.txt
>> !TXT_ERROR!
>>
>> Here you can see the state machines stop in different states.
>>
>> Although this problem is marginal in our project, it would be nice if
>> Ragel is absolute perfect :-)
>>
>> Best regards,
>> Dan
>>
>>
>>
>> _______________________________________________
>> ragel-users mailing list
>> ragel-users at complang.org
>> http://www.complang.org/mailman/listinfo/ragel-users
>
>
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