Re: [Tinycc-devel] make tcc reentrant

[Michael Matz]

Hi,

On Thu, 12 Dec 2019, grischka wrote:

> I assume Michael wrote that under the impression that there is still
> global data with lifetime beyond the tcc_compile function call, which
> was the case for example for the tokens and token hash table.
>
> I have to admit that I did remove that feature,

Luckily you did not.  For instance, there's a relation between sym->v and 
table_ident[sym->v]->str (e.g. via put_extern_sym).  The former is (now) 
per state, the latter is global.  If the latter would be made thread-local 
(but not per state) you'd have to record within the TCCState to which of 
the table_idents the sym->v entries are supposed to be relative to.  And 
in order to benefit from thread-local-ness of table_ident (i.e. to not 
have to write locking code around accesses to table_ident) you also would 
now have to make sure that the TCCState in question is only accessed from 
the thread in which it was created (which basically is the association of 
TCCState and table_ident above).

So, while that all would work out fine from a data race perspective, it 
doesn't seem to make much sense to me; you can then also move all still 
global data to TCCState (instead of making it thread-local) and even get a 
bit better code out of that (thread local data is slow to access).

But the current solution is IMHO even better, a nice core, and some glue 
code to support multiple states.  Everybody wins :)


Ciao,
Michael.