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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.
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Compile external fun expressions to literals
OTP-15003
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* sverker/driver-taints/OTP-14960:
erts: Include foreign static linked drivers in taints
erts: Fix harmless bug in macro IS_DRIVER_VERSION_GE
erts: Remove our own NIF modules from "taints"
erts: Refactor erts_static_nif_get_nif_init
erts: Add dynamic loaded drivers to list of "taints"
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detected by valgrind. We cannot compare monitor
in state MON_FREE before it's initialized.
Still not really kosher to access 'state' without lock or atomic-op.
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* john/erts/bwt-wt-dirty-schedulers/OTP-14959:
Add +sbwt/+swt analogues for dirty schedulers
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The expressions fun M:F/A, when all elements are literals are also
treated as a literal. Since they have consistent representation and
don't depend on the code currently loaded in the VM, this is safe.
This can provide significant performance improvements in code using such
functions extensively - a full function call to erlang:make_fun/3 is
replaced by a single move instruction and no register shuffling or
saving registers to stack is necessary. Additionally, compound data
types that contain such external functions as elements can be treated as
literals too.
The commit also changes the representation of external funs to be a
valid Erlang syntax and adds support for literal external funs to core
Erlang.
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Sharing these settings for all schedulers can degrade performance,
so it makes sense to be able to configure them separately.
This also changes the default busy-wait time to "short" for both
kinds of dirty schedulers.
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* rickard/signals/OTP-14589:
Fix VM probes compilation
Fix lock counting
Fix signal order for is_process_alive
Fix signal handling priority elevation
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* john/erts/nif-map-from-array/OTP-14954:
Add enif_make_map_from_arrays
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* john/erts/list-installed-nifs/OTP-14965:
Add an option to ?MODULE:module_info/1 for listing NIFs
Fix a misleading comment
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Communication between Erlang processes has conceptually always been
performed through asynchronous signaling. The runtime system
implementation has however previously preformed most operation
synchronously. In a system with only one true thread of execution, this
is not problematic (often the opposite). In a system with multiple threads
of execution (as current runtime system implementation with SMP support)
it becomes problematic. This since it often involves locking of structures
when updating them which in turn cause resource contention. Utilizing
true asynchronous communication often avoids these resource contention
issues.
The case that triggered this change was contention on the link lock due
to frequent updates of the monitor trees during communication with a
frequently used server. The signal order delivery guarantees of the
language makes it hard to change the implementation of only some signals
to use true asynchronous signaling. Therefore the implementations
of (almost) all signals have been changed.
Currently the following signals have been implemented as true
asynchronous signals:
- Message signals
- Exit signals
- Monitor signals
- Demonitor signals
- Monitor triggered signals (DOWN, CHANGE, etc)
- Link signals
- Unlink signals
- Group leader signals
All of the above already defined as asynchronous signals in the
language. The implementation of messages signals was quite
asynchronous to begin with, but had quite strict delivery constraints
due to the ordering guarantees of signals between a pair of processes.
The previously used message queue partitioned into two halves has been
replaced by a more general signal queue partitioned into three parts
that service all kinds of signals. More details regarding the signal
queue can be found in comments in the erl_proc_sig_queue.h file.
The monitor and link implementations have also been completely replaced
in order to fit the new asynchronous signaling implementation as good
as possible. More details regarding the new monitor and link
implementations can be found in the erl_monitor_link.h file.
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When supplied without an enclosing list, bitstrings were returned
as-is instead of badarging.
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A binary is a binary as long as its size in bits is evenly divisible
by 8, regardless of whether it has a bit offset or not.
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When supplied without an enclosing list, bitstrings were silently
truncated to [] instead of badarging.
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This has always worked but we lacked test coverage for it.
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Huge inputs weren't particularly useful and took forever to run, so
this commit winds it down to a more sane level that still causes
lots of yielding.
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* maint-20:
Updated OTP version
Update release notes
Update version numbers
erts: Add system_flags(erts_alloc,"+M?sbct *")
erts: Add age order first fit allocator strategies
erts: Refactor erl_ao_firstfit_alloc
erts: Add migration options "acnl" and "acfml"
kernel: Add os:cmd/2 with max_size option
erts: Add more stats for mbcs_pool
erts: Fix alloc_SUITE:migration
stdlib: Make ets_SUITE memory check try again
erts: Improve carrier pool search
erts: Improve alloc_SUITE:migration
erts: Refactor carrier dealloc migration
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into 'sverker/master/alloc-n-migration/ERIERL-88'
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into 'sverker/maint-20/alloc-n-migration/ERIERL-88'
OTP-14915
OTP-14916
OTP-14917
OTP-14918
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into 'sverker/maint-19/alloc-n-migration/ERIERL-88'
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to change sbct limit in runtime for chosen allocator type.
With great power comes great responsibility.
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ageffcaoff: Age First Fit Carrier, Address Order First Fit (within carrier)
ageffcbf : Age First Fit Carrier, Best Fit (within carrier)
ageffcaobf: Age First Fit Carrier, Address Order Best Fit (within carrier)
Prefer old carriers, the older the better.
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Fix rounding bug in float_to_list/2
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* fhunleth/binary_to_integer_chec/PR-1671/OTP-14879:
Fail if ':' is passed to binary_to_integer/2
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* maint:
stdlib: Handle Unicode when formatting stacktraces
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Example symptom:
1> float_to_list(0.145, [{decimals,1}]).
"0.2"
There were two problems in sys_double_to_chars_fast
1. Most serious was adding 0.55555555 / (10^D) instead of 0.5 / (10^D)
which imposed a 5.5% risk of a faulty rounding up.
2. Using fixpoint for frac_part which lost significant bits if F < 0.5
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See also ERL-553 and ERL-544 (commit c3ddb0f).
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* maint:
Fix encoding of filenames in stacktraces
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* rickard/file-encoding-stacktraces/OTP-14847/ERL-544:
Fix encoding of filenames in stacktraces
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Before:
1> binary_to_integer(<<":">>, 16).
3
After:
1> binary_to_integer(<<":">>, 16).
** exception error: bad argument
in function binary_to_integer/2
called as binary_to_integer(<<":">>,16)
Prior to this change, both list_to_integer/2 and binary_to_integer/2
would convert strings with values between ASCII '9' up to '0'+base for
base > 10. For example, when converting in base 16, you could pass ':',
';', '<', '=', '>', and '?' without getting an exception. This was due
to a missing check in c2int_is_invalid_char().
This change adds the missing check and a regression test for passing
':'. It also simplifies the code and tightens up an out-of-bounds check
to make it off-by-one rather than off-by-two.
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putenv(3) and friends aren't thread-safe regardless of how you slice
it; a global lock around all environment operations (like before)
keeps things safe as far as our own operations go, but we have
absolutely no control over what libc or a library dragged in by a
driver/NIF does -- they're free to call getenv(3) or putenv(3)
without honoring our lock.
This commit solves this by setting up an "emulated" environment which
can't be touched without going through our interfaces. Third-party
libraries can still shoot themselves in the foot but benign uses of
os:putenv/2 will no longer risk crashing the emulator.
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It crashed due to recursive calls to alloc_util
in carrier initialization test callback.
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to mix it up with some realloc calls.
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