R devel - Nov 2019 - Inconsistent behavior for the C AP's R_ParseVector() ?

Hi,

The behavior of
```
SEXP R_ParseVector(SEXP, int, ParseStatus *, SEXP);
```
defined in `src/include/R_ext/Parse.h` appears to be inconsistent depending
on the string to be parsed.

Trying to parse a string such as `"list(''=1+"` sets the
`ParseStatus` to incomplete parsing error but trying to parse
`"list(''=123"` will result in R sending a message to the
console
(followed but a crash):

```
R[write to console]: Error: attempt to use zero-length variable
nameR[write to console]: Fatal error: unable to initialize the JIT***
stack smashing detected ***: <unknown> terminated
```

Is there a reason for the difference in behavior, and is there a workaround ?

Thanks,


Laurent

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I found the following code comment in `src/main/gram.c`:

```

/* Memory leak

yyparse(), as generated by bison, allocates extra space for the parser
stack using malloc(). Unfortunately this means that there is a memory
leak in case of an R error (long-jump). In principle, we could define
yyoverflow() to relocate the parser stacks for bison and allocate say on
the R heap, but yyoverflow() is undocumented and somewhat complicated
(we would have to replicate some macros from the generated parser here).
The same problem exists at least in the Rd and LaTeX parsers in tools.
*/

```

Could this be related to be issue ?

Le sam. 30 nov. 2019 ? 14:04, Laurent Gautier <lgautier at gmail.com> a
?crit :
> Hi,
>
> The behavior of
> ```
> SEXP R_ParseVector(SEXP, int, ParseStatus *, SEXP);
> ```
> defined in `src/include/R_ext/Parse.h` appears to be inconsistent
> depending on the string to be parsed.
>
> Trying to parse a string such as `"list(''=1+"` sets the
> `ParseStatus` to incomplete parsing error but trying to parse
> `"list(''=123"` will result in R sending a message to the
console (followed but a crash):
>
> ```
> R[write to console]: Error: attempt to use zero-length variable nameR[write
to console]: Fatal error: unable to initialize the JIT*** stack smashing
detected ***: <unknown> terminated
> ```
>
> Is there a reason for the difference in behavior, and is there a workaround
?
>
> Thanks,
>
>
> Laurent
>
>
	[[alternative HTML version deleted]]

Hi again,

Beside R_ParseVector()'s possible inconsistent behavior, R's handling of
zero-length named elements does not seem consistent either:

```
> lst <- list()
> lst[[""]] <- 1
> names(lst)
[1] ""
> list("" = 1)
Error: attempt to use zero-length variable name
```

Should the parser be made to accept as valid what is otherwise possible
when using `[[<` ?


Best,

Laurent



Le sam. 30 nov. 2019 ? 17:33, Laurent Gautier <lgautier at gmail.com> a
?crit :
> I found the following code comment in `src/main/gram.c`:
>
> ```
>
> /* Memory leak
>
> yyparse(), as generated by bison, allocates extra space for the parser
> stack using malloc(). Unfortunately this means that there is a memory
> leak in case of an R error (long-jump). In principle, we could define
> yyoverflow() to relocate the parser stacks for bison and allocate say on
> the R heap, but yyoverflow() is undocumented and somewhat complicated
> (we would have to replicate some macros from the generated parser here).
> The same problem exists at least in the Rd and LaTeX parsers in tools.
> */
>
> ```
>
> Could this be related to be issue ?
>
> Le sam. 30 nov. 2019 ? 14:04, Laurent Gautier <lgautier at gmail.com>
a
> ?crit :
>
>> Hi,
>>
>> The behavior of
>> ```
>> SEXP R_ParseVector(SEXP, int, ParseStatus *, SEXP);
>> ```
>> defined in `src/include/R_ext/Parse.h` appears to be inconsistent
>> depending on the string to be parsed.
>>
>> Trying to parse a string such as `"list(''=1+"` sets
the
>> `ParseStatus` to incomplete parsing error but trying to parse
>> `"list(''=123"` will result in R sending a message to
the console (followed but a crash):
>>
>> ```
>> R[write to console]: Error: attempt to use zero-length variable
nameR[write to console]: Fatal error: unable to initialize the JIT*** stack
smashing detected ***: <unknown> terminated
>> ```
>>
>> Is there a reason for the difference in behavior, and is there a
workaround ?
>>
>> Thanks,
>>
>>
>> Laurent
>>
>>
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