Currently when LLDB has enough data in the debug information to import the `std` module,
it will just try to import it. However when debugging libraries where the sources aren't
available anymore, importing the module will generate a confusing diagnostic that
the module couldn't be built.
For the fallback mode (where we retry failed expressions with the loaded module), this
will cause the second expression to fail with a module built error instead of the
actual parsing issue in the user expression.
This patch adds checks that ensures that we at least have any source files in the found
include paths before we try to import the module. This prevents the module from being
loaded in the situation described above which means we don't emit the bogus 'can't
import module' diagnostic and also don't waste any time retrying the expression in the
fallback mode.
For the unit tests I did some refactoring as they now require a VFS with the files in it
and not just the paths. The Python test just builds a binary with a fake C++ module,
then deletes the module before debugging.
Fixes rdar://73264458
Reviewed By: JDevlieghere
Differential Revision: https://reviews.llvm.org/D95096
7ad49aec12 added a __memory subdirectory to libc++
but the code we use to find libc++ from the debug info support files wasn't
prepared to encounter unknown subdirectories within libc++. The import-std-module
tests automatically fell back to not importing the std module which caused
them to fail.
This patch removes our hardcoded exception for the 'experimental' subdirectory
and instead just ignores all subdirectories of c++/vX/ when searching the
support files.
This is how it should've been and brings it more in line with
std::string_view. There should be no functional change here.
This is mostly mechanical from a custom clang-tidy check, with a lot of
manual fixups. It uncovers a lot of minor inefficiencies.
This doesn't actually modify StringRef yet, I'll do that in a follow-up.
Summary:
At the moment, when trying to import the `std` module in LLDB, we look at the imported modules used in the compiled program
and try to infer the Clang configuration we need from the DWARF module-import. That was the initial idea but turned out to
cause a few problems or inconveniences:
* It requires that users compile their programs with C++ modules. Given how experimental C++ modules are makes this feature inaccessible
for many users. Also it means that people can't just get the benefits of this feature for free when we activate it by default
(and we can't just close all the associated bug reports).
* Relying on DWARF's imported module tags (that are only emitted by default on macOS) means this can only be used when using DWARF (and with -glldb on Linux).
* We essentially hardcoded the C standard library paths on some platforms (Linux) or just couldn't support this feature on other platforms (macOS).
This patch drops the whole idea of looking at the imported module DWARF tags and instead just uses the support files of the compilation unit.
If we look at the support files and see file paths that indicate where the C standard library and libc++ are, we can just create the module
configuration this information. This fixes all the problems above which means we can enable all the tests now on Linux, macOS and with other debug information
than what we currently had. The only debug information specific code is now the iteration over external type module when -gmodules is used (as `std` and also the
`Darwin` module are their own external type module with their own files).
The meat of this patch is the CppModuleConfiguration which looks at the file paths from the compilation unit and then figures out the include paths
based on those paths. It's quite conservative in that it only enables modules if we find a single C library and single libc++ library. It's still missing some
test mode where we try to compile an expression before we actually activate the config for the user (which probably also needs some caching mechanism),
but for now it works and makes the feature usable.
Reviewers: aprantl, shafik, jdoerfert
Reviewed By: aprantl
Subscribers: mgorny, abidh, JDevlieghere, lldb-commits
Tags: #c_modules_in_lldb, #lldb
Differential Revision: https://reviews.llvm.org/D67760
llvm-svn: 372716
Raphael Isemann