Re: Memory leak in bison-generated code

[Joel E. Denny]

On Fri, 6 Feb 2009, Jean Delvare wrote:

> Valgrind tells me that there's a memory leak in libsensors [1], in code
> which is generated by flex/bison:

> As this seemed to be the same problem as documented in this changelog
> entry:
> 
> 2006-11-10  Joel E. Denny  <address@hidden>
> 
>       Fix memory leaks in scanners generated by at least Flex 2.5.9 and
>       later.  Reported by Paul Eggert in

We generate Bison's own internal scanner/parser using Flex/Bison.  This 
ChangeLog entry is for a fix for a memory leak in that internal scanner.  
It does not affect memory leaks in a scanner or parser that you may 
generate using Flex/Bison.

> I upgraded to bison 2.4.1. Alas, the memory leak is still there, and as
> a matter of fact I don't see any call to yylex_destroy() in the
> generated code. If I do call sensors_yylex_destroy() manually then the
> memory leak goes away.

> So I am wondering: does it mean that I did something wrong in my code,
> which causes bison to not generate the call, or does it mean that the
> leak is not completely fixed yet?

It's not up to Bison to generate this call.  You must write the call just 
as we did for Bison's internal scanner.  Keep in mind that Flex generates 
your scanner, so see the Flex manual for more details.