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2018-06-18Update copyright yearHenrik Nord
2018-04-29Introduce is_map_key/2 guard BIFMichał Muskała
This complements the `map_get/2` guard BIF introduced in #1784. Rationale. `map_get/2` allows accessing map fields in guards, but it might be problematic in more complex guard expressions, for example: foo(X) when map_get(a, X) =:= 1 or is_list(X) -> ... The `is_list/1` part of the guard could never succeed since the `map_get/2` guard would fail the whole guard expression. In this situation, this could be solved by using `;` instead of `or` to separate the guards, but it is not possible in every case. To solve this situation, this PR proposes a `is_map_key/2` guard that allows to check if a map has key inside a guard before trying to access that key. When combined with `is_map/1` this allows to construct a purely boolean guard expression testing a value of a key in a map. Implementation. Given the use case motivating the introduction of this function, the PR contains compiler optimisations that produce optimial code for the following guard expression: foo(X) when is_map(X) and is_map_key(a, X) and map_get(a, X) =:= 1 -> ok; foo(_) -> error. Given all three tests share the failure label, the `is_map_key/2` and `is_map/2` tests are optimised away. As with `map_get/2` the `is_map_key/2` BIF is allowed in match specs.
2018-04-25Merge branch 'map-get-bif' of git://github.com/michalmuskala/otpBjörn Gustavsson
* 'map-get-bif' of git://github.com/michalmuskala/otp: Introduce map_get guard-safe function OTP-15037
2018-04-24Introduce map_get guard-safe functionMichał Muskała
Rationale Today all compound data types except for maps can be deconstructed in guards. For tuples we have `element/2` and for lists `hd/1` and `tl/1`. Maps are completely opaque to guards. This means matching on maps can't be abstracted into macros, which is often done with repetitive guards. It also means that maps have to be always selected whole from ETS tables, even when only one field would be enough, which creates a potential efficiency issue. This PR introduces an `erlang:map_get/2` guard-safe function that allows extracting a map field in guard. An alternative to this function would be to introduce the syntax for extracting a value from a map that was planned in the original EEP: `Map#{Key}`. Even outside of guards, since this function is a guard-BIF it is more efficient than using `maps:get/2` (since it does not need to set up the stack), and more convenient from pattern matching on the map (compare: `#{key := Value} = Map, Value` to `map_get(key, Map)`). Performance considerations A common concern against adding this function is the notion that "guards have to be fast" and ideally execute in constant time. While there are some counterexamples (`length/1`), what is more important is the fact that adding those functions does not change in any way the time complexity of pattern matching - it's already possible to match on map fields today directly in patterns - adding this ability to guards will niether slow down or speed up the execution, it will only make certain programs more convenient to write. This first version is very naive and does not perform any optimizations.
2018-04-19Merge pull request #1789 from ↵Lukas Larsson
christhekeele/remove-trace-terms-from-table-types-in-match-docs Remove trace-specific terms from docs for table-oriented matchspecs
2018-04-19Remove trace-specific terms from docs for table-oriented matchspecsChris Keele
This removes the matchspec instructions `is_seq_trace` and `get_tcw/0` from the documentation for table-oriented matchspecs. This is likely correct as both are already documented under "Functions Allowed Only for Tracing", despite appearing in the list of possible options for table specs. The following observations further back this change up: ```erl erlang:match_spec_test([whatever], [{'_', [], [{is_seq_trace}]}], trace). %=> {ok,true,[],[]} erlang:match_spec_test({whatever}, [{'_', [], [{is_seq_trace}]}], table). %=> {error,[{error,"Special form 'is_seq_trace' used in wrong %dialect."}]} erlang:match_spec_test([whatever], [{'_', [], [{get_tcw}]}], trace). %=> {ok,true,[],[]} erlang:match_spec_test({whatever}, [{'_', [], [{get_tcw}]}], table). %=> {error,[{error,"Function get_tcw/0 cannot be called in this context."}]} ```
2018-03-15Tracing MatchSpec docs updateVladimir Gordeev
I was running this code in shell and expected it to take default `self()` meta tracer, and start tracing `erlang:put/2`. ``` F = fun F() -> timer:sleep(5000), erlang:get(unique_field), erlang:put(unique_field, 123), F() end. erlang:trace_pattern({erlang, put, 2}, [{['$1', '_'], [{'==', '$1', unique_field}], []}], [global]). erlang:trace_pattern({erlang, get, 1}, [{['_'], [], [{trace, [], [call, timestamp]}]}], [meta]). Pid = spawn(F). ``` But tracing didn't start: ``` 6> flush(). Shell got {trace_ts,<0.70.0>,call, {erlang,get,[unique_field]}, {1521,118606,753838}} Shell got {trace_ts,<0.70.0>,call, {erlang,get,[unique_field]}, {1521,118611,754798}} Shell got {trace_ts,<0.70.0>,call, {erlang,get,[unique_field]}, {1521,118616,755705}} ok 7> erlang:trace_info(Pid, flags). {flags,[]} ``` Turns out that I had false expectations, that `{trace, _, _}` would enable tracing on that process, inheriting meta tracer process as consumer of trace messages. Instead it tried to take tracer from executing process (which is pointed out in docs). But there was none, so no tracing was started and flags were simply ignored (which is not that obvious from docs). Updated docs to point out that there are cases when flags would be simply ignored, and no tracing would start.
2016-09-01doc: Correct errors introduced by Editorial changesHans Bolinder
Fix some older errors as well.
2016-07-13erts: Review of documentation changesLukas Larsson
2016-07-13erts: Editorial changesxsipewe
2016-05-12erts: Add send/receive trace to match spec user guideSverker Eriksson
Introduce section/terminology "Match target".
2016-05-12erts: Fix confusion among match spec examplesSverker Eriksson
Tracing and ETS examples were not separated correctly under the corresponding headings.
2016-04-15erts: Add tracing examples in match spec docsLukas Larsson
2016-04-15erts: Implement tracer modulesLukas Larsson
Add the possibility to use modules as trace data receivers. The functions in the module have to be nifs as otherwise complex trace probes will be very hard to handle (complex means trace probes for ports for example). This commit changes the way that the ptab->tracer field works from always being an immediate, to now be NIL if no tracer is present or else be the tuple {TracerModule, TracerState} where TracerModule is an atom that is later used to lookup the appropriate tracer callbacks to call and TracerState is just passed to the tracer callback. The default process and port tracers have been rewritten to use the new API. This commit also changes the order which trace messages are delivered to the potential tracer process. Any enif_send done in a tracer module may be delayed indefinitely because of lock order issues. If a message is delayed any other trace message send from that process is also delayed so that order is preserved for each traced entity. This means that for some trace events (i.e. send/receive) the events may come in an unintuitive order (receive before send) to the trace receiver. Timestamps are taken when the trace message is generated so trace messages from differented processes may arrive with the timestamp out of order. Both the erlang:trace and seq_trace:set_system_tracer accept the new tracer module tracers and also the backwards compatible arguments. OTP-10267
2016-03-15update copyright-yearHenrik Nord
2015-06-18Change license text to APLv2Bruce Yinhe
2014-08-20Properly support maps in match_specsAnthony Ramine
2013-04-19Convert XML files to UTF-8Hans Bolinder
2012-03-30Update copyright yearsBjörn-Egil Dahlberg
2012-01-26Remove references to is_constant/1 from the match spec documentationBjörn Gustavsson
is_constant/1 was removed in R13B.
2010-06-02Add match_specification grammar documentation specifically for etsPatrik Nyblom
2010-05-17Fix typo in code exampleRaimo Niskanen
Reported by Uwe Dauernheim.
2010-02-10OTP-8422 Removed bogus "\011" character sequence in documentation.Hans Bolinder
2009-11-20The R13B03 release.OTP_R13B03Erlang/OTP