ValueObject is part of lldbCore for historical reasons, but conceptually
it deserves to be its own library. This does introduce a (link-time) circular
dependency between lldbCore and lldbValueObject, which is unfortunate
but probably unavoidable because so many things in LLDB rely on
ValueObject. We already have cycles and these libraries are never built
as dylibs so while this doesn't improve the situation, it also doesn't
make things worse.

The header includes were updated with the following command:

```
find . -type f -exec sed -i.bak "s%include \"lldb/Core/ValueObject%include \"lldb/ValueObject/ValueObject%" '{}' \;
```

Uses of (void) remain where they are for purposes other than an
assert variable.

On macOS, `sprintf` is deprecated, using `snprintf` is recommended instead.

Differential Revision: https://reviews.llvm.org/D147246

Currently, all data buffers are assumed to be writable. This is a
problem on macOS where it's not allowed to load unsigned binaries in
memory as writable. To be more precise, MAP_RESILIENT_CODESIGN and
MAP_RESILIENT_MEDIA need to be set for mapped (unsigned) binaries on our
platform.

Binaries are mapped through FileSystem::CreateDataBuffer which returns a
DataBufferLLVM. The latter is backed by a llvm::WritableMemoryBuffer
because every DataBuffer in LLDB is considered to be writable. In order
to use a read-only llvm::MemoryBuffer I had to split our abstraction
around it.

This patch distinguishes between a DataBuffer (read-only) and
WritableDataBuffer (read-write) and updates LLDB to use the appropriate
one.

rdar://74890607

Differential revision: https://reviews.llvm.org/D122856

The StringPrinter class was using a Process instance to read memory.
This automatically prevented it from working before starting the
program.

This patch changes the class to use the Target object for reading
memory, as targets are always available. This required moving
ReadStringFromMemory from Process to Target.

This is sufficient to make frame/target variable work, but further
changes are necessary for the expression evaluator. Preliminary analysis
indicates the failures are due to the expression result ValueObjects
failing to provide an address, presumably because we're operating on
file addresses before starting. I haven't looked into what would it take
to make that work.

Differential Revision: https://reviews.llvm.org/D113098

lldb_private::DataExtractor contains DataBufferSP m_data_sp which is
relatively expensive to copy (due to multi-threading locking).

llvm::DataExtractor does not have this problem as it uses StringRef
instead.

The copy constructor is explicit as otherwise it is easy to make
unintended modification of a local copy instead of a caller's instance
(D107470 but that is llvm::DataExtractor).

Reviewed By: clayborg

Differential Revision: https://reviews.llvm.org/D107485

The C headers are deprecated so as requested in D102845, this is replacing them
all with their (not deprecated) C++ equivalent.

Reviewed By: shafik

Differential Revision: https://reviews.llvm.org/D103084

Support printing strings which contain invalid utf8 sub-sequences, e.g.
strings like "hello world \xfe", instead of bailing out with "Summary
Unavailable".

I took the opportunity here to delete some hand-rolled utf8 -> utf32
conversion code and replace it with calls into llvm's Support library.

rdar://61554346

The m_size and m_data members of DecodedCharBuffer are meant to be
private.

Summary:
Languages can have different ways of formatting special characters.
E.g. when debugging C++ code a string might look like "\b", but when
debugging Swift code the same string would look like "\u{8}".

To make this work, plugins override GetStringPrinterEscapingHelper.
However, because there's a large amount of subtly divergent work done in
each override, we end up with large amounts of duplicated code. And all
the memory smashers fixed in one copy of the logic (see D73860) don't
get fixed in the others.

IMO the GetStringPrinterEscapingHelper is overly general and hard to
use. I propose deleting it and replacing it with an EscapeStyle enum,
which can be set as needed by each plugin.

A fix for some swift-lldb memory smashers falls out fairly naturally
from this deletion (https://github.com/apple/llvm-project/pull/1046). As
the swift logic becomes really tiny, I propose moving it upstream as
part of this change. I've added unit tests to cover it.

rdar://61419673

Reviewers: JDevlieghere, davide

Subscribers: mgorny, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D77843