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was fixed along with Trac #10224

The leading hash in a comment confused CPP, though
it worked fine on my machine. Apologies.

SpecConstr was generating a rule LHS with nested casts,
which the simplifier then optimised away.  Result: unbound
template variables.

Easily fixed.  See Note [SpecConstr call patterns]

This was causing Trac #10627.
See Note [Substitute lazily] in CoreSubst.

The bug was introduced by
   commit 30c17e70
    Author: simonpj@microsoft.com <unknown>
    Date:   Thu Nov 25 17:23:56 2010 +0000
    Substitution should just substitute, not optimise

The fix is not to optimise the RHS as well as not-optimising the LHS!
The simplifier does the right thing in Simplify.simplRule

This seems to have improved by a bit

b5e1944e started using a single GC
generation yet didn't update this.

D898 was primarily intended to fix hangs in the event that iconv was
unavailable (namely #10298 and #7695). In addition to this fix, it also
introduced self-contained handling of ANSI terminals to allow compiled
executables to run in minimal environments lacking iconv.

However, the behavior that the patch introduced is highly suspicious.
Specifically, it gives the user a UTF-8 encoding even if they requested
ASCII.

This has the potential to break quite a lot of code. At very least it
breaks GHC's Unicode terminal detection logic, which attempts to catch
an invalid character when encoding a pair of smart-quotes. Of course,
this exception will never be thrown if a UTF-8 encoder is used.

Here we use the `char8` encoding to handle requests for ASCII encodings
in the event that we find iconv to be non-functional.

Fixes #10623.

Test Plan: Validate with T8959a

Reviewers: rwbarton, hvr, austin, hsyl20

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1059

GHC Trac Issues: #10623

Also remove 't' and 's' from ALL_WAYS; they don't exist.

Differential Revision: https://phabricator.haskell.org/D1055

Improve error message fundeps, especially when PolyKinds means that
the un-determined variables are (invisible) kind variables.

See Trac #10570.

Adopts sugggestion in Trac #10224, comment:3

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: bgamari, austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1060

GHC Trac Issues: #10624

Responding to Trac #10608 and Trac #10351, I've reverted
to making type inference infer structured constraint like
    f :: C [t] => t -> t
even if -XFlexibleContexts is not set.  That elicits an
error message suggesting the flag.  The result is more
helpful than the error message you get otherwise.

Relates to Trac #10595

Previously we would build up another `map (-N)` thunk
for every word in the bitmap. Now we strictly accumulate the position
and carry out a single ``map (`subtract` accum)``.

`Bitmap.intsToBitmap` showed up in the profile while compiling a 
testcase of #7450 (namely a program containing a record type with large 
number of fields which derived `Read`). The culprit was 
`CmmBuildInfoTables.procpointSRT.bitmap`. On the testcase (with 4096 
fields), the profile previously looked like,

```
	total time  =      307.94 secs   (307943 ticks @ 1000 us, 1 
processor)
	total alloc = 336,797,868,056 bytes  (excludes profiling 
overheads)

COST CENTRE              MODULE              %time %alloc

lintAnnots               CoreLint             17.2   25.8
procpointSRT.bitmap      CmmBuildInfoTables   11.3   25.2
FloatOutwards            SimplCore             7.5    1.6
flatten.lookup           CmmBuildInfoTables    4.0    3.9
...
```

After this fix it looks like,
```
	total time  =      256.88 secs   (256876 ticks @ 1000 us, 1 
processor)
	total alloc = 255,033,667,448 bytes  (excludes profiling 
overheads)

COST CENTRE              MODULE              %time %alloc

lintAnnots               CoreLint             20.3   34.1
FloatOutwards            SimplCore             9.1    2.1
flatten.lookup           CmmBuildInfoTables    4.8    5.2
pprNativeCode            AsmCodeGen            3.7    4.3
simplLetUnfolding        Simplify              3.6    2.2
StgCmm                   HscMain               3.6    2.1
```
Signed-off-by: Ben Gamari <ben@smart-cactus.org>

Test Plan: Validate

Reviewers: austin, simonpj

Reviewed By: simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1041

GHC Trac Issues: #7450

Out of scope variables now generate HsUnboundVar,
and the fixity re-jigging wasn't taking this into
account.

The other one is MkId.hs.

Should have been part of 9aa0e4b2.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Export the data types `GiveGCStats`, `DoCostCentres`, `DoHeapProfiles`,
and `DoTrace`, as well as the type synonyms `Time` and `RtsNat`. The
above data types appear as fields in the `-Stats` data types in
`GHC.RTS.Flags`, but since they only have `Show` instances, it is
practically impossible to due anything useful with the above types
unless they are exported.

Reviewers: hvr, ekmett, austin, ezyang, bgamari

Reviewed By: bgamari

Subscribers: thomie, bgamari

Differential Revision: https://phabricator.haskell.org/D1030

GHC Trac Issues: #9970

Test Plan: validate

Reviewers: goldfire, austin, simonpj, bgamari

Reviewed By: bgamari

Subscribers: simonpj, rwbarton, thomie, bgamari

Differential Revision: https://phabricator.haskell.org/D1026

GHC Trac Issues: #10596

Summary:
This patch switches -fPIC on for every invocation of GHC
on OpenBSD/AMD64 platform. The reason is OpenBSD's support
for PIE (PIC for executables) hence -fPIC is also needed
for GHC compiled code.

Fixes #10597

Reviewers: austin

Subscribers: thomie, bgamari

Differential Revision: https://phabricator.haskell.org/D1027

This generalizes forever to depend on Applicative, rather than Monad.

This was proposed a month ago
(https://mail.haskell.org/pipermail/libraries/2015-May/025711.html).

Differential Revision: https://phabricator.haskell.org/D1045

Alexander found a interesting case:
1. We have a queue of two waiters in a blocked_queue
2. first file descriptor changes state to RUNNABLE,
   second changes to INVALID
3. awaitEvent function dequeued RUNNABLE thread to a
   run queue and attempted to dequeue INVALID descriptor
   to a run queue.

Unqueueing INVALID fails thusly:
        #3  0x000000000045cf1c in barf (s=0x4c1cb0 "removeThreadFromDeQueue: not found")
                               at rts/RtsMessages.c:42
        #4  0x000000000046848b in removeThreadFromDeQueue (...) at rts/Threads.c:249
        #5  0x000000000049a120 in removeFromQueues (...) at rts/RaiseAsync.c:719
        #6  0x0000000000499502 in throwToSingleThreaded__ (...) at rts/RaiseAsync.c:67
        #7  0x0000000000499555 in throwToSingleThreaded (..) at rts/RaiseAsync.c:75
        #8  0x000000000047c27d in awaitEvent (wait=rtsFalse) at rts/posix/Select.c:415

The problem here is a throwToSingleThreaded function that tries
to unqueue a TSO from blocked_queue, but awaitEvent function
leaves blocked_queue in a inconsistent state while traverses
over blocked_queue:

      case RTS_FD_IS_READY:
          IF_DEBUG(scheduler,
              debugBelch("Waking up blocked thread %lu\n",
                         (unsigned long)tso->id));
          tso->why_blocked = NotBlocked;
          tso->_link = END_TSO_QUEUE;              // Here we break the queue head
          pushOnRunQueue(&MainCapability,tso);
          break;
Signed-off-by: Sergei Trofimovich <siarheit@google.com>

Test Plan: tested on a sample from T10590

Reviewers: austin, bgamari, simonmar

Reviewed By: bgamari, simonmar

Subscribers: qnikst, thomie, bgamari

Differential Revision: https://phabricator.haskell.org/D1024

GHC Trac Issues: #10590, #4934

Depends on D864.

Previous behaviour was ErrorCall, which might mask issues in tests 
using -fdefer-type-errors
Signed-off-by: David Kraeutmann <kane@kane.cx>

Test Plan: Test whether the error thrown is indeed TypeError and not 
ErrorCall.

Reviewers: hvr, nomeata, austin

Reviewed By: nomeata, austin

Subscribers: nomeata, simonpj, thomie

Differential Revision: https://phabricator.haskell.org/D866

GHC Trac Issues: #10284

This commit renames the Size module in the native code generator to
Format, as proposed by a todo, as well as adjusting parameter names in
other modules that use it.

Test Plan: validate

Reviewers: austin, simonmar, bgamari

Reviewed By: simonmar, bgamari

Subscribers: bgamari, simonmar, thomie

Projects: #ghc

Differential Revision: https://phabricator.haskell.org/D865

Adds a flag -fwarn-deferred-type-errors similar to -fwarn-typed-holes.
Changes the boolean flag of -fdefer-type-errors to a 3-state flag 
similar to the one used by -fdefer-typed-holes/-fwarn-typed-holes.

Test Plan: Since only the absence of deferred type error warnings when 
-fno-warn-deferred-type-errors is passed has to be tested, I duplicated 
a test case checking -fdefer-type-errors and adjusted it accordingly.

Reviewers: nomeata, simonpj, austin, thomie, bgamari, hvr

Reviewed By: nomeata, simonpj, austin, thomie, bgamari, hvr

Subscribers: bgamari, simonpj, nomeata, thomie

Projects: #ghc

Differential Revision: https://phabricator.haskell.org/D864

GHC Trac Issues: #10283