update #1919

It is only used in benchmarks and 'go test' now has command line
options to enable profiling as appropriate (but maybe it didn't in
2014).

* pkg/proc: avoid target process leaks.

Target process should exit when dlv launch failed.

Fix #2017.

Changes implementations of proc.Registers interface and the
op.DwarfRegisters struct so that floating point registers can be loaded
only when they are needed.
Removes the floatingPoint parameter from proc.Thread.Registers.
This accomplishes three things:

1. it simplifies the proc.Thread.Registers interface
2. it makes it impossible to accidentally create a broken set of saved
   registers or of op.DwarfRegisters by accidentally calling
   Registers(false)
3. it improves general performance of Delve by avoiding to load
   floating point registers as much as possible

Floating point registers are loaded under two circumstances:

1. When the Slice method is called with floatingPoint == true
2. When the Copy method is called

Benchmark before:

BenchmarkConditionalBreakpoints-4   	       1	4327350142 ns/op

Benchmark after:

BenchmarkConditionalBreakpoints-4   	       1	3852642917 ns/op

Updates #1549

* cmd/dlv,debugger: Improve dlv trace and trace command output

This patch improves the `dlv trace` subcommand output by reducing the
noise that is generated and providing clearer more concise information.

Also adds new tests closing a gap in our testing (we previously never
really tested this subcommand).

This patch also fixes the `dlv trace` REPL command to behave like the
subcommand in certain situations. If the tracepoint is for a function,
we now show function arguements and return values properly.

Also makes the overall output of the trace subcommand clearer.

Fixes #2027

Fixes #2037

* Adds launch request support for program args

* Combine types of function parameters
Co-authored-by: NPolina Sokolova <polinasok@users.noreply.github.com>

The option is "source-list-line-count". It defaults to 5, which was previously
hardcoded in printfile(), but now you can change it dynamically, for instance:

 $ config source-list-line-count 20
 $ list

When trying to compile tests in a package that does not contain tests
'go' emits an error message on stdout instead of stderr. Let the 'go'
command write to stdout too.

Fixes #2042

Fixes #2026

Unexport `GetDebugServerAbsolutePath` and avoid unnecessary repeated calls.
Remove `os.Stat` because `Exec.LookPath` has already used `os.Stat`.And Fix
some comments.

* Add no-op handlers for unsupported requests

* Fix whitespace

* Add couple of missing unsupported requests

* More comments

* Separate errors for unsupported and not-yet-implemented requests.

* Fix go.mod/sum dependencies
Co-authored-by: NPolina Sokolova <polinasok@users.noreply.github.com>

Splits the compileUnits slice between images so that we can search for
an offset inside the debug info of a specific image file.

When there is a single piece and it's a register value just return it.
This is important for clang compiled programs which will use DW_OP_regN
to specify the value of the frame base.

Mirroring the way this is implemented in the Go runtime and introducing
a type that will be useful to support the call injection changes in Go
1.15

pickCurrentThread should always run.

Fixes #2028

On linux platform, we simply treated `/proc/$pid/exe` as the
executable of targeting process when doing `dlv attach`. The
`/proc/$pid/exe` is a symbol link of the real executable file.
Delve couldn't find the corrsponding external debug file based on the
symbol link:

```
could not attach to pid $pid: could not open debug info
```

The fix is to evaluate the symbol links to the actual executable path.

Allow user to specify output syntax flavor of assembly in the
disassemble command.

Close #415

This test will occasionally hang in SetBreakpoint/WriteMemory

The process could quit while we are inside stop, we should report the
error otherwise the following code will try to send on the closed
ptrace channel.
Fixes a sporadic error in TestIssue1101.

Reduces test timeout by one minute so that Go will timeout before
Travis-CI and report useful informations about the hang.

Fixes a long standing dangling TODO item.

Embed the debugger config object in the service config object to avoid needless duplication of fields.

We should not return error directly which set `fileFound` to be true
if there's a compileUnit without line section.

Commit changes after executing gen-usage-docs.go script

Related to #1995

Add --continue as a valid flag for the attach command by decorating attachCommand
with the continueOnStart variable.

Fixes #1995

This flag allows users on UNIX systems to set the tty for the program
being debugged by Delve. This is useful for debugging command line
applications which need access to their own TTY, and also for
controlling the output of the debugged programs so that IDEs may open a
dedicated terminal to show the output for the process.

* dwarf/line: implement DW_LNE_set_discriminator

We don't use the discriminator field in any way but we need to at least
parse it to support debub_line programs that use it.

* dwarf/line: support parsing DWARF4 debug_line sections

There is an extra field maximum_operations_per_instruction that is used
for VLIW CPUs. We don't support this feature but we have to at least
parse the field to not crash.

* gdbserial/gdbserver: Dynamically resolve debugserver binary

Instead of hardcoding the absolute path to the Command Line
Tools (CLT) binary, will attempt to resolve the path at the
$PATH, or at the Xcode bundle. If none are available, will
fallback to the default CLT location.

Fixes #986

* gdbserial/gdbserver: Log outgoing executed commands

Add logging to capture the executable and associated arguments used
in LLDBLaunch and LLDBAttach

Related to #986

* gdbserial/gdbserver: Add unit tests for helper function

Define unit tests for helper function. Setup each test to temporarily make
PATH variable, and file system changes, and subsequently revert them.

Related to #986

* gdbserial/gdbserver: Lazily load function

Lazily obtain absolute path to avoid increasing load times.

Remove flaky tests.

Related to #986

1. Adds a note to the documentation describing how to use 'go get' in
   modules mode
2. Removes the '-u' option which, when 'go get' is used incorrectly
   will make 'go' try to compile Delve with unsupported dependencies
3. Removed obsolete note about Go 1.5 vendor experiment.

Fixes #1988