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please add an option to enable debug symbols only #6238
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Comment author: @mshinwell I think this is a reasonable thing to do. Watch this space. |
Comment author: @gasche While I think this is a reasonable feature, I think that in the long term the way to go is rather to provide more control to performance-conscious users of which raises will trigger backtrace recording (eg. the raise-variants work of Alain). Indeed, there should be a sweet spot where most exceptions used for control flow do not record any trace, only actually exceptional exceptions do, and you have a system that is both efficient (essentially as the no-trace one) and auditable in case of unplanned failure (a good reason to have some backtraces even in production). I can understand people disabling everything for absolute performances (and right now it's probably easier to implement), but long-term I think that's more of a minority use-case. Of course if someone is ready to do the work, that's great in any case. |
Comment author: @damiendoligez Gabriel, your argument addresses backtraces only, not the bound-checking and disabled optimizations. |
Comment author: @alainfrisch
Have you seen cases where keeping multiple call sites for caml_ml_array_bound_error yields a noticeable performance penalty?
Since the request is to have a mode with maximal runtime performance (while keeping debugging information), I don't think that bytecode is relevant. Alain |
Comment author: @damiendoligez In any case, the request is for adding debugging info to the executable, while guaranteeing no run-time overhead, and this seems quite reasonable to me. |
Comment author: @gasche Mark, is it time for a gentle ping? |
Comment author: @mshinwell Please see the comment on the pull request |
This issue has been open one year with no activity. Consequently, it is being marked with the "stale" label. What this means is that the issue will be automatically closed in 30 days unless more comments are added or the "stale" label is removed. Comments that provide new information on the issue are especially welcome: is it still reproducible? did it appear in other contexts? how critical is it? etc. |
Just for info, we would appreciate such a full-speed plus debug info binary mode. |
Thanks @jberdine for your help with bug triaging (and your feedback) these days. |
This issue has been open one year with no activity. Consequently, it is being marked with the "stale" label. What this means is that the issue will be automatically closed in 30 days unless more comments are added or the "stale" label is removed. Comments that provide new information on the issue are especially welcome: is it still reproducible? did it appear in other contexts? how critical is it? etc. |
@gasche do you think this could be a "good first issue"? |
Yes, but I think that we should start gathering a consensus on the naming of such an option, because while the implementation may be relatively simple, picking a good name probably is not. |
This issue has been open one year with no activity. Consequently, it is being marked with the "stale" label. What this means is that the issue will be automatically closed in 30 days unless more comments are added or the "stale" label is removed. Comments that provide new information on the issue are especially welcome: is it still reproducible? did it appear in other contexts? how critical is it? etc. |
The feature wish seems reasonable to me, and seems to have only be stuck due to naming paralysis. |
In case someone is waiting for name inspiration, |
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Sorry for the naïve question, but as the issue description above mentions native code, what "debug symbols" are we talking about? The location information for each instruction? |
previously (at the time this issue was created) it was function names, afaihs now we also have source locations |
Original bug ID: 6238
Reporter: @ygrek
Assigned to: @mshinwell
Status: acknowledged (set by @mshinwell on 2013-11-18T16:29:38Z)
Resolution: open
Priority: normal
Severity: feature
Target version: undecided
Category: back end (clambda to assembly)
Related to: #6728
Monitored by: @gasche @ygrek @yakobowski @alainfrisch
Bug description
Rationale:
currently option -g mixes several things up - generation debug symbols, storing backtrace information, adding more precise bounds checking, disabling some optimizations (in bytecode).
For profiling one usually wants the same binary code that is run in production but with debug symbols. So the speed of the code is the same, but there is some extra information available on demand, and this build can be run on production at highest speed and then profiled live if any problem arises. Option -g makes this approach less attractive because of incurred performance cost (e.g. storing backtrace).
Can we please have another option to only write out (native, i.e. DWARF) debugging info and perform no other changes to generated code?
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