On Wed, Apr 29, 2015 at 10:48 AM, Adrian Prantl <[email protected]> wrote:
> > On Apr 29, 2015, at 10:04 AM, Eric Christopher <[email protected]> wrote: > > > > On Wed, Apr 29, 2015 at 9:58 AM Eric Christopher <[email protected]> > wrote: > >> On Wed, Apr 29, 2015 at 8:20 AM Adrian Prantl <[email protected]> wrote: >> >>> >>> > On Apr 28, 2015, at 6:26 PM, David Blaikie <[email protected]> wrote: >>> >>> > Could you revert & I'll look into getting you a reduced test >>> case/demonstration of the issue? (can you run GDB 7.5? Perhaps a simple >>> test case would demonstrate the issue if you're lucky, otherwise I can >>> reduce one from the failing test case) >>> >>> I reverted the commit in r236110. I probably won’t need a reduction — my >>> guess from the log is that gdb expects a local variable to be present. >>> >>> My suggestion is to emit local artificial shadow variables and then >>> weaken the Verifier to not verify artificial variables. In a next step, we >>> could use the new debugger tuning target feature to make the artificial >>> local variables and the weakened verifier a gdb-specific behavior, file a >>> bug against gdb, and eventually remove it altogether. >>> >>> >> FWIW I don't want to use the "tuning" parameters to also affect >> correctness. >> > > OK. Dave and I debated this a little in person, here's a proposal: > > by default it will have the gdb specific behavior, but if you're tuning > for lldb (or any other debugger I guess?) it won't be there. > > > Thoughts? > > > I think it’s a fair assumption that many debuggers won’t deal very well > with anonymous local variables, from that perspective this is the right > decision. > (Nitpick: If it is only needed for GDB then it doesn’t seem right to make > it the global default, because tuning for gdb will be the default on all > non-lldb/sce platforms anyway.) > > I really want to push towards making the debug info handling stricter, so > I’m unhappy about having the frontend willfully emit broken IR at the > moment. But, I also haven’t found a way to emit the local shadow variables > in a way that makes the verifier happy and isn’t entirely gross in other > respects. I’ll keep looking for a better way to emit this without having to > relax the verifier. > Im curious though - why is this harder to support than, say, ASan's habit of smooshing all the variables into a single alloca? They seem rather similar to me, but I'm probably missing something. - David > > -- adrian >
_______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
