On macOS 10.14 Apple changed the command line tools so that system
headers now need to be manually installed.

Instead of adding one extra install step to the install procedure add a
build tag to allow compilation of delve without the native backend on
macOS. By default (i.e. when using `go get`) this is how delve will be
compiled on macOS, the make script is changed to enable compiling the
native backend if the required dependencies have been installed.

Insure that both configuration still build correctly on Travis CI and
change the documentation to describe how to compile the native backend
and that it isn't normally needed.

Fixes #1359

Add a flag to Stackframe that indicates where the stack frame is the
bottom-most frame of the stack. This allows clients to know whether the
stack trace terminated normally or if it was truncated because the
maximum depth was reached.
Add a truncation message to the 'stack' command.

Adds -defer flag to the stack command that decorates the stack traces
by associating each stack frame with its deferred calls.

Reworks proc.next to use this feature instead of using proc.DeferPC,
laying the groundwork to implement #1240.

Implements structured logging via Logrus. This gives us a logger per
boundry that we care about, allowing for easier parsing of logs if users
have more than one log option enabled. Also, cleans up a lot of
conditionals in the code by simply silencing the logger at creation as
opposed to conditionally logging everywhere.

A user complained on the mailing list about having continuous
"optimized function warnings" on non-optimized functions when using 1.9.
This commit fixes the problem by disabling optimized function detection
on 1.9 and earlier (where it's impossible) and adds a test so we don't
break it again in the future.

Displays the return values of the current function when we step out of
it after executing a step, next or stepout command.

Implementation of this feature is tricky: when the function has
returned the return variables are not in scope anymore. Implementing
this feature requires evaluating variables that are out of scope, using
a stack frame that doesn't exist anymore.

We can't calculate the address of these variables when the
next/step/stepout command is initiated either, because between that
point and the time where the stepout breakpoint is actually hit the
goroutine stack could grow and be moved to a different memory address.

If we don't build artifacts aren't removed after the tests run. Also
add a check to prevent this mistake from reoccuring.

printcontext should use SelectedGoroutine instead of trusting that the
goroutine running on current thread matches the SelectedGoroutine.

When the user switches to a parked goroutine CurrentThread and
SelectedGoroutine will diverge.

Almost all calls to printcontext are safe, they happen after a continue
command returns when SelectedGoroutine and CurrentThread always agree,
but the calls in frameCommand and listCommand are wrong.

Additionally we should stop reporting an error when the debugger is
stopped on an unknown PC address.

* Extend the "frame" command to set the current frame.

Command

  frame 3

sets up so that subsequent "print", "set", "whatis" command
will operate on frame 3.

  frame 3 print foo

continues to work.

Added "up", "down". They move the current frame up or down.

Implementation note:

This changes removes "scopePrefix" mode from the terminal/command.go and instead
have the command examine the goroutine/frame value to see if it is invoked in a
scoped context.

* Rename Command.Frame -> Command.frame.

Fixes #1090

* command/terminal: allow restart to change process args

Add -args flag to "restart" command. For example, "restart -args a b c" will
pass args a b c to the new process.

Add "-c" flag to pass the checkpoint name. This is needed to disambiguate the
checkpoint name and arglist.

Reverted unnecessary changes.

* Applied reviewer comments.

Vendored argv.

Change the syntax of restart. When the target is is in recording mode, it always
interprets the args as a checkpoint. Otherwise, it interprets the args as
commandline args. The flag "-args" is still there, to handle the case in which
the user wants to pass an empty args on restart.

* Add restartargs.go.

Change "restart -args" to "restart -noargs" to clarify that this flag is used to
start a process with an empty arg.

So far we have evaluated the locspec "+0" the same way we evaluate all
"+n" locspecs, this means that we turn the current PC into a file:line
pair, then we turn back the file:line into a PC address.

Normally this is harmless, however all autogenerated code returns the
source position "<autogenerated>:1" which resolves back to the very
first autogenerated instruction in the code.

This messes up the behaviour of the "disassemble" command which uses
the locspec "+0" to figure out what code to disassemble if no arguments
are passed.

We should make +0 always resolve to the current PC (of the given scope)
so that clients can use +0 as a default locspec.

Prints the frame and frame pointer offsets for each frame.

Fixes #927, #644

Fixes #940

Can't get the trace directory from the server after we disconnect from
it.

Updates #893

When there's a error reading the stack trace the call stack itself
could be corrupted and we should return the partial stacktrace that we
have.

Fixes #868

* Fix various issues detected by megacheck

I've ran honnef.co/go/tools/cmd/megacheck and fixed a few of the
things that came up there.

* Cleanup using Gogland

Other debuggers can be instructed to decorate the stacktrace with the
value of SP. Our SP equivalent is the frame offset, since we can add it
to the Stackframe structure without incurring into added costs we
should, so that frontends can use it if they want.

If CurrentThread isn't running a goroutine SelectedGoroutine can be
nil, do not blindly dereference it.

Fixes #827

Implements #727

- always print a header with the path to the file being displayed
- always evaluate the linespec argument, even if a scope prefix is present

Fixes #711, #713

Expressions such as:

 frame 0    list
 frame   0   list
 on abreakpoint     print x
 goroutine    1    frame     0     list

should all execute correctly

Fixes #712

The test in question tries to 'next' over a call to wg.Done, this is
not guaranteed to succeed, if the goroutine gets suspended after
wg.Done has notified the waiting group but before returning to
main.dostuff the program could quit before the goroutine is resumed.

On Windows we can sometimes encounter threads stopped in locations for
which we do not have entries in debug_frame.
These cases seem to be due to calls to Windows API in the go runtime,
we can still produce a (partial) stack trace in this circumstance by
following frame pointers (starting with BP).
We still prefer debug_frame entries when available since go functions
do not have frame pointers before go1.8.

Allows quoted substrings in build-flags flag. This fixes a build
problem on windows where the default build flags must contain a space.

Fixes #634 and #638

This version preserves the order of requests, allows the
client to switch between API versions and introduces a
way to send notifications to the client (see TODO item at:
proc/proc_linux.go:325).

Fixes #523, #571

* documentation: copied old documentation from wiki

* command: better online documentation

Help without arguments prints just a short summary for each command,
help followed by a command prints the command's syntax and a longer
explanation.

* documentation: automatically generate Documentation/cli/README.md

* proc: bugfix: StepInto can not function when temp bps exist

* terminal,service: auto-continue during next and step

Make dlv call continue automatically when a breakpoint is hit on a
different goroutine during a next or step operation.
Added API hooks to implement the other solution to this problem (cancel
the next/step operation if a different breakpoint is hit).

Fixes #387

* service/api: Removed unused fields of service/api.Function

* proc/eval: Set return variable name to input expression

* all: fine-grained control of loadValue for better variable printing

Makes proc.(*Variable).loadValue loading parameters configurable
through one extra argument of type LoadConfig.
This interface is also exposed through the API so clients can control
how much of a variable delve should read.

New API version with better backwards compatibility plus mechanism to
select the API version that a headless instance should use.

Adds service/test/cmd/typecheckrpc.go to type check the RPC interface.

When the vars, locals, or args commands return no results, nothing is

printed out to the terminal. This commit makes these commands print a

message like `(no locals)` when there is nothing to show. This feedback

is more descriptive of what is being returned than an empty string.

Implements extensible mechanism to specify which commands accept
prefixes (goroutine, frame, on) instead of hardcoding them in
a switch.

Implements #240

Fixes #411