Also log errors from the lsof command on failure.
(That's how the missing environment was discovered.)
Updates #25628
Change-Id: I71594f60c15d0d254d5d4a86deec7431314c92ff
Reviewed-on: https://go-review.googlesource.com/c/go/+/201717
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
These functions are not necessary and are not called anywhere.
Change-Id: I1c0d814ba3044c27e3626ac9e6052d8154140404
Reviewed-on: https://go-review.googlesource.com/c/go/+/201697
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
It seems that windowsZones.xml file has moved to Github. I opened
http://unicode.org/cldr/data/common/supplemental/windowsZones.xml
in my browser, and it redirected me to
https://github.com/unicode-org/cldr/blob/master/common/supplemental/windowsZones.xml
Very nice of them.
And we could see windowsZones.xml change history now. We could even
probably file issues against this file, if we find problems.
Anyway, this CL adjusts genzabbrs.go to use new GitHub location.
I also run 'go generate' command with updated genzabbrs.go to update
zoneinfo_abbrs_windows.go.
Fixes#34917
Change-Id: I69b71a4e02edd999435738ecb225a6f9793a66d5
Reviewed-on: https://go-review.googlesource.com/c/go/+/201378
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
This CL adds -d=checkptr as a compile-time option for adding
instrumentation to check that Go code is following unsafe.Pointer
safety rules dynamically. In particular, it currently checks two
things:
1. When converting unsafe.Pointer to *T, make sure the resulting
pointer is aligned appropriately for T.
2. When performing pointer arithmetic, if the result points to a Go
heap object, make sure we can find an unsafe.Pointer-typed operand
that pointed into the same object.
These checks are currently disabled for the runtime, and can also be
disabled through a new //go:nocheckptr annotation. The latter is
necessary for functions like strings.noescape, which intentionally
violate safety rules to workaround escape analysis limitations.
Fixes#22218.
Change-Id: If5a51273881d93048f74bcff10a3275c9c91da6a
Reviewed-on: https://go-review.googlesource.com/c/go/+/162237
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This was spotted in CL 200767. This change just ensures internal
packages match their equivalents in x/mod.
Also pulled in test added in CL 201517.
Change-Id: I51d23d62697c256548f411930fcb6bccce51bf34
Reviewed-on: https://go-review.googlesource.com/c/go/+/201497
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
1. Change mapencode.encode to use fmt.Error rather than MarshalerError.
MarshalerError refer to MarshalJSON, but mapencode.encode does not use that.
2. Add sourceFunc field to MarshalerError to record the name of the function
that creates the error, so that the Error method can report it correctly.
Fixes#29753
Change-Id: I186c2fac8470ae2f9e300501de3730face642230
Reviewed-on: https://go-review.googlesource.com/c/go/+/184119
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This a revert of CL 174437 and follow up fix CL 201317.
The s390x assembly in this package makes use of an instruction
(specifically KDSA) which is not supported by the current build
machine. Remove this assembly for now, we can revisit this
functionality once we have a newer build machine and can ensure
that this assembly is well tested.
Updates #34927.
Change-Id: I779286fa7d9530a254b53a515ee76b1218821f2f
Reviewed-on: https://go-review.googlesource.com/c/go/+/201360
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Allow TempDir to create directories with predictable
prefixes and suffixes, separated by the last "*", for example:
"prefix*suffix"
will now expand to
"prefix" + <RANDOM_VALUE> + "suffix"
RELNOTE=yes
Fixes#33805.
Change-Id: I85fa73ae6a684ce820d1810c82a60765eb9c4a42
Reviewed-on: https://go-review.googlesource.com/c/go/+/198488
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Generate inline code at defer time to save the args of defer calls to unique
(autotmp) stack slots, and generate inline code at exit time to check which defer
calls were made and make the associated function/method/interface calls. We
remember that a particular defer statement was reached by storing in the deferBits
variable (always stored on the stack). At exit time, we check the bits of the
deferBits variable to determine which defer function calls to make (in reverse
order). These low-cost defers are only used for functions where no defers
appear in loops. In addition, we don't do these low-cost defers if there are too
many defer statements or too many exits in a function (to limit code increase).
When a function uses open-coded defers, we produce extra
FUNCDATA_OpenCodedDeferInfo information that specifies the number of defers, and
for each defer, the stack slots where the closure and associated args have been
stored. The funcdata also includes the location of the deferBits variable.
Therefore, for panics, we can use this funcdata to determine exactly which defers
are active, and call the appropriate functions/methods/closures with the correct
arguments for each active defer.
In order to unwind the stack correctly after a recover(), we need to add an extra
code segment to functions with open-coded defers that simply calls deferreturn()
and returns. This segment is not reachable by the normal function, but is returned
to by the runtime during recovery. We set the liveness information of this
deferreturn() to be the same as the liveness at the first function call during the
last defer exit code (so all return values and all stack slots needed by the defer
calls will be live).
I needed to increase the stackguard constant from 880 to 896, because of a small
amount of new code in deferreturn().
The -N flag disables open-coded defers. '-d defer' prints out the kind of defer
being used at each defer statement (heap-allocated, stack-allocated, or
open-coded).
Cost of defer statement [ go test -run NONE -bench BenchmarkDefer$ runtime ]
With normal (stack-allocated) defers only: 35.4 ns/op
With open-coded defers: 5.6 ns/op
Cost of function call alone (remove defer keyword): 4.4 ns/op
Text size increase (including funcdata) for go cmd without/with open-coded defers: 0.09%
The average size increase (including funcdata) for only the functions that use
open-coded defers is 1.1%.
The cost of a panic followed by a recover got noticeably slower, since panic
processing now requires a scan of the stack for open-coded defer frames. This scan
is required, even if no frames are using open-coded defers:
Cost of panic and recover [ go test -run NONE -bench BenchmarkPanicRecover runtime ]
Without open-coded defers: 62.0 ns/op
With open-coded defers: 255 ns/op
A CGO Go-to-C-to-Go benchmark got noticeably faster because of open-coded defers:
CGO Go-to-C-to-Go benchmark [cd misc/cgo/test; go test -run NONE -bench BenchmarkCGoCallback ]
Without open-coded defers: 443 ns/op
With open-coded defers: 347 ns/op
Updates #14939 (defer performance)
Updates #34481 (design doc)
Change-Id: I51a389860b9676cfa1b84722f5fb84d3c4ee9e28
Reviewed-on: https://go-review.googlesource.com/c/go/+/190098
Reviewed-by: Austin Clements <austin@google.com>
Fix issues that make these tests pass:
- TestDialerLocalAddr: return error if local address is not IPv4 for
"tcp4" network.
- TestInterfaceAddrs, TestInterfaceUnicastAddrs: don't assume each
interface has only one address. It may have more than one or none.
- TestConcurrentPreferGoResolversDial: should be skipped on Plan 9.
- TestListenMulticastUDP: remove IP from `announce` command and don't
mix IPv4 address with IPv6 address in `addmulti` command.
Fixes#34931
Change-Id: Ie0fdfe19ea282e5d6d6c938bf3c9139f8f5b0308
Reviewed-on: https://go-review.googlesource.com/c/go/+/201397
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
While building a simple hello world binary, there are total 858277 calls
to writeUleb during the assembler phase out of which 836625 (97%) are less than 7 bits.
Using a simple micro-benchmark like this:
func BenchmarkUleb(b *testing.B) {
var buf bytes.Buffer
for i := 0; i < b.N; i++ {
writeUleb128(&buf, 42)
buf.Reset()
}
}
We get the following results with the fast path enabled.
name old time/op new time/op delta
Uleb-4 8.45ns ± 2% 7.51ns ± 2% -11.16% (p=0.000 n=10+10)
Applying the time taken to the number of calls, we get roughly 6% improvement
in total time taken for writeUleb128.
We also apply the change to the function in linker to make it consistent.
Change-Id: I9fe8c41df1209f5f3aa7d8bd0181f1b0e536ceb5
Reviewed-on: https://go-review.googlesource.com/c/go/+/201177
Run-TryBot: Agniva De Sarker <agniva.quicksilver@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
I used too small a size for buffers, which can cause a panic in some testing.
The new buffer size is generous and sufficient for all purposes.
Fixes#34927Fixes#34928
Change-Id: Icdbbfed5da87fe3757be40dfd23182b37ec62d58
Reviewed-on: https://go-review.googlesource.com/c/go/+/201317
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The Go spec requires
If a deferred function value evaluates to nil, execution
panics when the function is invoked, not when the "defer"
statement is executed.
On Wasm and AIX, currently we actually emit a nil check at the
point of defer statement, which will make it panic too early.
This CL fixes this.
Also, on Wasm, now the nil function will be passed through
deferreturn to jmpdefer, which does an explicit nil check and
calls sigpanic if it is nil. This sigpanic, being called from
assembly, is ABI0. So change the assembler backend to also
handle sigpanic in ABI0.
Fixes#34926.
Updates #8047.
Change-Id: I28489a571cee36d2aef041f917b8cfdc31d557d4
Reviewed-on: https://go-review.googlesource.com/c/go/+/201297
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Do not modify the underlying Rat denominator when calling
one of the accessors Float32, Float64; verify that we don't
modify the Rat denominator when calling Inv, Sign, IsInt, Num.
Fixes#34919.
Reopens#33792.
Change-Id: Ife6d1252373f493a597398ee51e7b5695b708df5
Reviewed-on: https://go-review.googlesource.com/c/go/+/201205
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This new facility will be used by future CLs in this series.
Change the only blocking call to netpoll to do the right thing when
netpoll returns an empty list.
Updates #6239
Updates #27707
Change-Id: I58b3c2903eda61a3698b1a4729ed0e81382bb1ed
Reviewed-on: https://go-review.googlesource.com/c/go/+/171821
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
In the tzdata database CEST is not recognized as a timezone name.
It is used as the abbreviated name for daylight saving time in
Central Europe. Avoid using CEST in documentation as it suggests
that programs can parse dates that use CEST, which will typically
fail on Unix systems.
Updates #34913
Change-Id: I4b22f7d06607eb5b066812a48af58edd95498286
Reviewed-on: https://go-review.googlesource.com/c/go/+/201197
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
This changes fixes an oversight in wakeScavenger which would cause ready
to be called off of the system stack. This change makes it so that
wakeScavenger calls goready, which switches to the system stack before
calling ready.
Fixes#34773.
Change-Id: Icb13f180b4d8fdd47c921eac1b896e3dd49e43b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/200999
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
When a subsequent load/store of a ptr makes the nil check of that pointer
unnecessary, if their lines differ, change the line of the load/store
to that of the nilcheck, and attempt to rehome the load/store position
instead.
This fix makes profiling less accurate in order to make panics more
informative.
Fixes#33724
Change-Id: Ib9afaac12fe0d0320aea1bf493617facc34034b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/200197
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
CL 196781 added map[int64]uint32 to the set of things printed with %v.
Fixes#34907
Change-Id: If4a13e86cfb4b691988f5fb70449ae23760f5789
Reviewed-on: https://go-review.googlesource.com/c/go/+/201079
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
It was possible to get 'go env' to break itself:
$ go env -w GO111MODULE=bad
$ go env
go: unknown environment setting GO111MODULE=bad
We already check if the variable name is known. In some cases like
GO111MODULE, we also know what the variable's valid values are. Enforce
it when writing the variable, not just when fetching it.
Fixes#34880.
Change-Id: I10d682087c69f3445f314fd4473644f694e255f7
Reviewed-on: https://go-review.googlesource.com/c/go/+/200867
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Before this CL, inequality was recorded in a bit matrix using
SSA IDs. This allowed to record inequality for SSA values that
we didn't know any relation in the partial order of. Unfortunately,
this also means that inequality is harder to use within the poset
itself as there is not fast way to map from internal poset indices
and SSA values.
Since we will need to check for inequality in following CLs within
code that lost track of SSA values, switch to use a bit matrix
of poset indices instead. This requires always allocate a poset
node (as a new root) for values that are first seen in a SetNonEqual
call, but it doesn't sound like a big problem. The other solution
(creating and maintaining a reverse map from poset indices to SSA
values) seem more complicated and memory hungry.
Change-Id: Ic917485abbe70aef7ad6fa98408e5430328b6cd9
Reviewed-on: https://go-review.googlesource.com/c/go/+/196782
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Currently, constants in posets, in addition to being stored in
a DAG, are also stored as SSA values in a slice. This allows to
quickly go through all stored constants, but it's not easy to search
for a specific constant.
Following CLs will benefit from being able to quickly find
a constants by value in the poset, so change the constants
structure to a map. Since we're at it, don't store it as
*ssa.Value: poset always uses dense uint32 indices when
referring a node, so just switch to it.
Using a map also forces us to have a single node per
constant value: this is a good thing in the first place,
so this CL also make sure we never create two nodes for
the same constant value.
Change-Id: I099814578af35f935ebf14bc4767d607021f5f8b
Reviewed-on: https://go-review.googlesource.com/c/go/+/196781
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
The comment in both functions referred to the wrong header and I made
the checks easier to read.
Change-Id: Ifb46729cee631a3305f557863818e3487b8eed71
Reviewed-on: https://go-review.googlesource.com/c/go/+/71753
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Add an internal mode to simplify debugging of posets
by checking the integrity after every mutation. Turn
it on within SSA checked builds.
Change-Id: Idaa8277f58e5bce3753702e212cea4d698de30ca
Reviewed-on: https://go-review.googlesource.com/c/go/+/196780
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Fixes the docs to correctly match the implementation
and also adds a test locking-in the behavior to prevent
any accidental future regressions on the docs.
Fixes#33545
Change-Id: I6fdac6048cce8ac99beaa2db0dfc81d0dccc10f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/200798
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The IsClosureVar, IsOutputParamHeapAddr, Assigned, Addrtaken,
InlFormal, and InlLocal flags are only interesting for ONAME nodes, so
it's better to set these flags on Name.flags instead of Node.flags.
Two caveats though:
1. Previously, we would set Assigned and Addrtaken on the entire
expression tree involved in an assignment or addressing operation.
However, the rest of the compiler only actually cares about knowing
whether the underlying ONAME (if any) was assigned/addressed.
2. This actually requires bumping Name.flags from bitset8 to bitset16,
whereas it doesn't allow shrinking Node.flags any. However, Name has
some trailing padding bytes, so expanding Name.flags doesn't cost any
memory.
Passes toolstash-check.
Change-Id: I7775d713566a38d5b9723360b1659b79391744c2
Reviewed-on: https://go-review.googlesource.com/c/go/+/200898
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
For Go 1.13 we introduced Header.Clone and it returns
nil if a nil Header is cloned. Unfortunately, though,
this exported Header.Clone nil behavior differed from
the old Go 1.12 and earlier internal header clone
behavior which always returned non-nil Headers.
This CL fixes the places where that distinction mattered.
Fixes#34878
Change-Id: Id19dea2272948c8dd10883b18ea7f7b8b33ea8eb
Reviewed-on: https://go-review.googlesource.com/c/go/+/200977
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Add to the testcase originally created for issue 34577 so
as to also trigger the error condition for issue 34852 (the
two bugs are closely related).
Updates #34577.
Updates #34852.
Change-Id: I2347369652ce500184347606b2bb3e76d802b204
Reviewed-on: https://go-review.googlesource.com/c/go/+/201017
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
For GOROOT packages, we were adding -unsafeptr=false to prevent unsafe.Pointer
checks. But the flag also got passed to invocations of go vet with a custom
vet tool. To prevent this from happening, we add this flag only when no
tools are passed.
Fixes#34053
Change-Id: I8bcd637fd8ec423d597fcdab2a0ceedd20786019
Reviewed-on: https://go-review.googlesource.com/c/go/+/200957
Run-TryBot: Agniva De Sarker <agniva.quicksilver@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
These are unused since the darwin port switched to libc calls in
CL 148457.
Change-Id: I309bb5b0a52c9069484e7a649d4a652efcb8e160
Reviewed-on: https://go-review.googlesource.com/c/go/+/200866
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This flag is supposed to indicate whether the expression is
"addressable"; but in practice, we infer this from other
attributes about the expression (e.g., n.Op and n.Class()).
Passes toolstash-check.
Change-Id: I19352ca07ab5646e232d98e8a7c1c9aec822ddd0
Reviewed-on: https://go-review.googlesource.com/c/go/+/200897
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This pseudo-Class was previously used by the importer code to optimize
processing duplicate inline bodies, since we didn't actually care
about the declarations in those contexts.
This functionality is no longer needed with indexed exports, since we
now only process function bodies as needed (and never more than once).
Passes toolstash-check.
Change-Id: I7eab0cb16925ab777079c2a20731dbcfd63cf195
Reviewed-on: https://go-review.googlesource.com/c/go/+/200899
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Make it a bit more relaxed on the expected fairness, as fastrand()
isn't a truly perfect random number generator.
Fixes#34808
Change-Id: Ib55b2bbe3c1bf63fb4f446fd1291eb1236efc33b
Reviewed-on: https://go-review.googlesource.com/c/go/+/200857
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Some nameservers alter the case of records as they return, e.g
.google.COM or .Google.com.
However according to RFC4343, DNS name should be treated in case insensitive fashion.
This CL will fix case sensitive testcases.
Fixes#34781
Change-Id: I5f9f6a41ddc1c61993e8d1f934ef0febddc3adc1
Reviewed-on: https://go-review.googlesource.com/c/go/+/200277
Reviewed-by: Andrei Tudor Călin <mail@acln.ro>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
When assessing whether A <= B, the poset's OrderedOrEqual has a passing
condition which permits A <= B, but is not sufficient to infer that A <= B.
This CL removes that incorrect passing condition.
Having identified that A and B are in the poset, the method will report that
A <= B if any of these three conditions are true:
(1) A and B are the same node in the poset.
- This means we know that A == B.
(2) There is a directed path, strict or not, from A -> B
- This means we know that, at least, A <= B, but A < B is possible.
(3) There is a directed path from B -> A, AND that path has no strict edges.
- This means we know that B <= A, but do not know that B < A.
In condition (3), we do not have enough information to say that A <= B, rather
we only know that B == A (which satisfies A <= B) is possible. The way I
understand it, a strict edge shows a known, strictly-ordered relation (<) but
the lack of a strict edge does not show the lack of a strictly-ordered relation.
The difference is highlighted by the example in #34802, where a bounds check is
incorrectly removed by prove, such that negative indexes into a slice
succeed:
n := make([]int, 1)
for i := -1; i <= 0; i++ {
fmt.Printf("i is %d\n", i)
n[i] = 1 // No Bounds check, program runs, assignment to n[-1] succeeds!!
}
When prove is checking the negative/failed branch from the bounds check at n[i],
in the signed domain we learn (0 > i || i >= len(n)). Because prove can't learn
the OR condition, we check whether we know that i is non-negative so we can
learn something, namely that i >= len(n). Prove uses the poset to check whether
we know that i is non-negative. At this point the poset holds the following
relations as a directed graph:
-1 <= i <= 0
-1 < 0
In poset.OrderedOrEqual, we are testing for 0 <= i. In this case, condition (3)
above is true because there is a non-strict path from i -> 0, and that path
does NOT have any strict edges. Because this condition is true, the poset
reports to prove that i is known to be >= 0. Knowing, incorrectly, that i >= 0,
prove learns from the failed bounds check that i >= len(n) in the signed domain.
When the slice, n, was created, prove learned that len(n) == 1. Because i is
also the induction variable for the loop, upon entering the loop, prove previously
learned that i is in [-1,0]. So when prove attempts to learn from the failed
bounds check, it finds the new fact, i > len(n), unsatisfiable given that it
previously learned that i <= 0 and len(n) = 1.
Fixes#34802
Change-Id: I235f4224bef97700c3aa5c01edcc595eb9f13afc
Reviewed-on: https://go-review.googlesource.com/c/go/+/200759
Run-TryBot: Zach Jones <zachj1@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>
Reviewed-by: Keith Randall <khr@golang.org>
