At Facebook, we link OpenMP code with libomp instead of libgomp. We have
an internal patch to drgn to do this, as it can't be done by setting
CFLAGS/LDFLAGS. Let's add a way to specify the OpenMP library at
configure time so that we can drop the internal patch.
Currently the drgn version number is defined in drgn.h.in, and configure
and setup.py both parse it out of there. However, now that we're
generating drgn.h anyways, it's easier to make configure.ac the source
of truth.
Rebase on 0.178. The only additional change needed is to pass
--disable-debuginfod to configure.
Based on:
2c7c4037 elfutils.spec.in: Sync with fedora spec, remove rhel/fedora specifics.
With the following patches:
configure: Add --disable-programs
configure: Add --disable-shared
configure: Fix -D_FORTIFY_SOURCE=2 check when CFLAGS contains -Wno-error
libcpu: compile i386_lex.c with -Wno-implicit-fallthrough
libdwfl: add interface for attaching to/detaching from threads
libdwfl: cache Dwfl_Module and Dwarf_Frame for Dwfl_Frame
libdwfl: add interface for evaluating DWARF expressions in a frame
In order to retrieve registers from stack traces, we need to know what
registers are defined for a platform. This adds a small DSL for defining
registers for an architecture. The DSL is parsed by an awk script that
generates the necessary tables, lookup functions, and enum definitions.
Now that we have the bundled version of elfutils, build it from libdrgn
and link to it. We can also get rid of the elfutils version checks from
the libdrgn code.
I went back and forth on using setuptools or autotools for the Python
extension, but I eventually settled on using only setuptools after
fighting to get the two to integrate well. However, setuptools is kind
of crappy; for one, it rebuilds every source file when rebuilding the
extension, which is really annoying for development. automake is a
better designed build system overall, so let's use that for the
extension. We override the build_ext command to build using autotools
and copy things where setuptools expects them.
The current mixed Python/C implementation works well, but it has a
couple of important limitations:
- It's too slow for some common use cases, like iterating over large
data structures.
- It can't be reused in utilities written in other languages.
This replaces the internals with a new library written in C, libdrgn. It
includes Python bindings with mostly the same public interface as
before, with some important improvements:
- Types are now represented by a single Type class rather than the messy
polymorphism in the Python implementation.
- Qualifiers are a bitmask instead of a set of strings.
- Bit fields are not considered a separate type.
- The lvalue/rvalue terminology is replaced with reference/value.
- Structure, union, and array values are better supported.
- Function objects are supported.
- Program distinguishes between lookups of variables, constants, and
functions.
The C rewrite is about 6x as fast as the original Python when using the
Python bindings, and about 8x when using the C API directly.
Currently, the exposed API in C is fairly conservative. In the future,
the memory reader, type index, and object index APIs will probably be
exposed for more flexibility.
