The addition of the StopCondition in the lldb_private layer meant that
clearing a breakpoint condition with:

sb_break.SetCondition(nullptr);

now crashes. Also, GetCondition for an empty condition used to return a
nullptr, but now it returns "".

This patch fixes that crash and makes the SB GetCondition always return
nullptr for an empty condition.

LLDB breakpoint conditions take an expression that's evaluated using the
language of the code where the breakpoint is located. Users have asked
to have an option to tell it to evaluate the expression in a specific
language.

This is feature is especially helpful for Swift, for example for a
condition based on the value in memory at an offset from a register.
Such a condition is pretty difficult to write in Swift, but easy in C.

This PR adds a new argument (-Y) to specify the language of the
condition expression. We can't reuse the current -L option, since you
might want to break on only Swift symbols, but run a C expression there
as per the example above.

rdar://146119507

This RP changes some Breakpoint-related interfaces to return errors. On
its own these improvements are small, but they encourage better error
handling going forward. There are a bunch of other candidates, but these
were the functions that I touched while working on #146602.

This patch removes all of the Set.* methods from Status.

This cleanup is part of a series of patches that make it harder use the
anti-pattern of keeping a long-lives Status object around and updating
it while dropping any errors it contains on the floor.

This patch is largely NFC, the more interesting next steps this enables
is to:
1. remove Status.Clear()
2. assert that Status::operator=() never overwrites an error
3. remove Status::operator=()

Note that step (2) will bring 90% of the benefits for users, and step
(3) will dramatically clean up the error handling code in various
places. In the end my goal is to convert all APIs that are of the form

`    ResultTy DoFoo(Status& error)
`
to

`    llvm::Expected<ResultTy> DoFoo()
`
How to read this patch?

The interesting changes are in Status.h and Status.cpp, all other
changes are mostly

` perl -pi -e 's/\.SetErrorString/ = Status::FromErrorString/g' $(git
grep -l SetErrorString lldb/source)
`
plus the occasional manual cleanup.

This PR is in reference to porting LLDB on AIX.

Link to discussions on llvm discourse and github:
1.  https://discourse.llvm.org/t/port-lldb-to-ibm-aix/80640
2.  #101657 

The complete changes for porting are present in this draft PR:
https://github.com/llvm/llvm-project/pull/102601

The changes on this PR are intended to avoid namespace collision for
certain typedefs between lldb and other platforms:
1. tid_t --> lldb::tid_t
2. offset_t --> lldb::offset_t

StreamFile subclasses Stream (from lldbUtility) and is backed by a File
(from lldbHost). It does not depend on anything from lldbCore or any of its
sibling libraries, so I think it makes sense for this to live in
lldbHost instead.

Differential Revision: https://reviews.llvm.org/D157460

LLDB should guarantee that the strings returned by SBAPI methods
live forever. I went through every method that returns a string and made
sure that it was added to the ConstString StringPool before returning if
it wasn't obvious that it was already doing so.
I've also updated the docs to document this behavior.

Differential Revision: https://reviews.llvm.org/D150804

In order to run a {break,watch}point command, lldb can resolve to the
script interpreter to run an arbitrary piece of code or call into a
user-provided function. To do so, we will generate a wrapping function,
where we first copy lldb's internal dictionary keys into the
interpreter's global dictionary, copied inline the user code before
resetting the global dictionary to its previous state.

However, {break,watch}point commands can optionally return a value that
would tell lldb whether we should stop or not. This feature was
only implemented for breakpoint commands and since we inlined the user
code directly into the wrapping function, introducing an early return,
that caused lldb to let the interpreter global dictionary tinted with the
internal dictionary keys.

This patch fixes that issue while also adding the stopping behaviour to
watchpoint commands.

To do so, this patch refactors the {break,watch}point command creation
method, to let the lldb wrapper function generator know if the user code is
a function call or a arbitrary expression.

Then the wrapper generator, if the user input was a function call, the
wrapper function will call the user function and save the return value into
a variable. If the user input was an arbitrary expression, the wrapper  will
inline it into a nested function, call the nested function and save the
return value into the same variable. After resetting the interpreter global
dictionary to its previous state, the generated wrapper function will return
the varible containing the return value.

rdar://105461140

Differential Revision: https://reviews.llvm.org/D144688

Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>

* Include SetCallback in SBBreakpointLocation, similar as in SBBreakpoint.
* Add test_breakpoint_location_callback test as part of TestMultithreaded.

Reviewed By: werat, JDevlieghere

Differential Revision: https://reviews.llvm.org/D133689

Co-authored-by: Andy Yankovsky <weratt@gmail.com>