Re: [sqlite] Two problems in latest version of lempar.c

[Benjamin Franksen]

Hi Richard

thanks for the quick response!

On 04.10.2016 14:21, Richard Hipp wrote:
> On 10/4/16, Benjamin Franksen  wrote:
>> I am using the lemon parser generator in a project
>> (http://www-csr.bessy.de/control/SoftDist/sequencer/). I updated the
>> lemon parser template tools/lempar.c to the latest available version and
>> found two problems, reported by gcc:
>>
>> ./snl.c: In function ‘yy_destructor’:
>> ./snl.c:116:36: warning: unused variable ‘presult’ [-Wunused-variable]
>>  #define snlParserARG_FETCH  Node **presult  = yypParser->presult
> 
> This can be resolved by using the "presult" variable in one of your 
> destructors.

I have no destructors. The parser I am generating is part of a compiler
that never frees any resources (until it exits).

Anyway, ParseARG_STORE is used once in lempar.c to actually store the
extra argument and four times to suppress unused variable warnings
(according to the source comments), so I guess a fifth time won't do
much harm ;-)

>> ./snl.c: In function ‘snlParser’:
>> ./snl.c:2446:33: warning: comparison of distinct pointer types lacks a
>> cast [enabled by default]
>>  while( yypParser->yytos >= >yystack
> 
> I think the latest trunk check-in may fix this.
> https://www.sqlite.org/src/info/3a9d802fda105856
> 
> But that fix is untested, as the error handling logic where this code
> is found is #ifdef-ed out in SQLite.  Please give the latest a try and
> let me know if that fails to fix the problem.

The fix works fine, thanks. I don't know why I didn't see it when I
looked at the repo today (I did intend to grab the latest version from
the trunk), probably made a mistake navigating the web interface.

Cheers
Ben
-- 
"Make it so they have to reboot after every typo." ― Scott Adams



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Re: [sqlite] Two problems in latest version of lempar.c

[Richard Hipp]

On 10/4/16, Benjamin Franksen  wrote:
> Hello
>
> I am using the lemon parser generator in a project
> (http://www-csr.bessy.de/control/SoftDist/sequencer/). I updated the
> lemon parser template tools/lempar.c to the latest available version and
> found two problems, reported by gcc:
>
> ./snl.c: In function ‘yy_destructor’:
> ./snl.c:116:36: warning: unused variable ‘presult’ [-Wunused-variable]
>  #define snlParserARG_FETCH  Node **presult  = yypParser->presult

This can be resolved by using the "presult" variable in one of your destructors.

> ./snl.c: In function ‘snlParser’:
> ./snl.c:2446:33: warning: comparison of distinct pointer types lacks a
> cast [enabled by default]
>  while( yypParser->yytos >= >yystack

I think the latest trunk check-in may fix this.
https://www.sqlite.org/src/info/3a9d802fda105856

But that fix is untested, as the error handling logic where this code
is found is #ifdef-ed out in SQLite.  Please give the latest a try and
let me know if that fails to fix the problem.

-- 
D. Richard Hipp
d...@sqlite.org
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[sqlite] Two problems in latest version of lempar.c

[Benjamin Franksen]

Hello

I am using the lemon parser generator in a project
(http://www-csr.bessy.de/control/SoftDist/sequencer/). I updated the
lemon parser template tools/lempar.c to the latest available version and
found two problems, reported by gcc:

./snl.c: In function ‘yy_destructor’:
./snl.c:116:36: warning: unused variable ‘presult’ [-Wunused-variable]
 #define snlParserARG_FETCH  Node **presult  = yypParser->presult
^
./snl.c:1031:3: note: in expansion of macro ‘snlParserARG_FETCH’
   snlParserARG_FETCH;
   ^
./snl.c: In function ‘snlParser’:
./snl.c:2446:33: warning: comparison of distinct pointer types lacks a
cast [enabled by default]
 while( yypParser->yytos >= >yystack

The first is a harmless warning which can be suppressed by using the
snlParserARG_STORE macro in yy_destructor right after
snlParserARG_FETCH, as is done similarly in a number of other functions
in lempar.c.

The second one is *NOT* harmless. The '&' before yypParser->yystack is
indeed wrong and could in corner cases lead to a crash or worse a
security vulnerability.

Cheers
Ben

PS: I am not subscribed, so please add my address to any replies.
-- 
"Make it so they have to reboot after every typo." ― Scott Adams



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