If there is a relocation for a particular FDE, print it as well. This is
mainly meant for human consumption (otherwise, there's no way to tell
which function a given (relocatable) FDE refers to). For testing of
relocation generation, I'd still recommend using the regular relocation
dumper, as this code will not detect (e.g.) any superfluous relocations.
I've considered handling relocations inside the SFrameParser class, but
I couldn't find an elegant way to do that. Right now, I don't have a use
case for resolving relocations there as lldb (my other use case for
SFrameParser) will always operate on linked objects.
This reapplies #152650 with a build fix for clang-11 (need explicit
template parameters for ArrayRef construction) and avoiding the
default-in-a-switch-covering-enum warning. It also adds two new tests.
The original commit message was:
The trickiest part here is that the FREs have a variable size, in two
(or three?) dimensions:
- the size of the StartAddress field. This determined by the FDE they
are in, so it is uniform across all FREs in one FDE.
- the number and sizes of offsets following the FRE. This can be
different for each FRE.
While vending this information through a template API would be possible,
I believe such an approach would be very unwieldy, and it would still
require a sequential scan through the FRE list. This is why I'm
implementing this by reading the data into a common data structure using
the fallible iterator pattern.
For more information about the SFrame unwind format, see the
[specification](https://sourceware.org/binutils/wiki/sframe) and the
related
[RFC](https://discourse.llvm.org/t/rfc-adding-sframe-support-to-llvm/86900).
The trickiest part here is that the FREs have a variable size, in two
(or three?) dimensions:
- the size of the StartAddress field. This determined by the FDE they
are in, so it is uniform across all FREs in one FDE.
- the number and sizes of offsets following the FRE. This can be
different for each FRE.
While vending this information through a template API would be possible,
I believe such an approach would be very unwieldy, and it would still
require a sequential scan through the FRE list. This is why I'm
implementing this by reading the data into a common data structure using
the fallible iterator pattern.
For more information about the SFrame unwind format, see the
[specification](https://sourceware.org/binutils/wiki/sframe) and the
related
[RFC](https://discourse.llvm.org/t/rfc-adding-sframe-support-to-llvm/86900).
## Purpose
This patch is one in a series of code-mods that annotate LLVM’s public
interface for export. This patch annotates symbols that were recently
added to LLVM without proper annotations. The annotations currently have
no meaningful impact on the LLVM build; however, they are a prerequisite
to support an LLVM Windows DLL (shared library) build.
## Background
This effort is tracked in #109483. Additional context is provided in
[this
discourse](https://discourse.llvm.org/t/psa-annotating-llvm-public-interface/85307),
and documentation for `LLVM_ABI` and related annotations is found in the
LLVM repo
[here](https://github.com/llvm/llvm-project/blob/main/llvm/docs/InterfaceExportAnnotations.rst).
## Overview
The bulk of these changes were generated automatically using the
[Interface Definition Scanner (IDS)](https://github.com/compnerd/ids)
tool, followed formatting with `git clang-format`.
The following manual adjustments were also applied after running IDS:
- Add `LLVM_EXPORT_TEMPLATE` and `LLVM_TEMPLATE_ABI` annotations to
explicitly instantiated instances of `llvm::object::SFrameParser`.
## Validation
Local builds and tests to validate cross-platform compatibility. This
included llvm, clang, and lldb on the following configurations:
- Windows with MSVC
- Windows with Clang
- Linux with GCC
- Linux with Clang
- Darwin with Clang
This PR adds the SFrameParser class and uses it from llvm-readobj to
dump the section contents. Currently, it only supports parsing the
SFrame section header. Other parts of the section will be added in
follow-up patches.
llvm-readobj uses the same sframe flag syntax as GNU readelf, but I have
not attempted match the output format of the tool. I'm starting with the
"llvm" output format because it's easier to generate and lets us
tweak the format to make it useful for testing the generation code. If
needed, support for the GNU format could be added by overriding this
functionality in the GNU ELF Dumper.
For more information, see the [sframe
specification](https://sourceware.org/binutils/wiki/sframe) and the
related
[RFC](https://discourse.llvm.org/t/rfc-adding-sframe-support-to-llvm/86900).
