LLDB tracks where any imported `clang::Decl` originally came from via a simple
map from 'imported decl' to 'original decl'. That information is used to later
complete parts of the Decl when more information is requested about a certain
Decl (e.g., via the ExternalASTSource interface from Clang).
When finding the 'original decl' for a given decl, the ASTImporterDelegate
essentially just recursively follows the previously mentioned map from
'imported' to 'original decl' until it can find any further 'original decl'. The
final found decl is then the one that will be imported. The recursion is
necessary as in LLDB we don't just import decls from one ASTContext to another,
but also from one ASTContext to another via a (potentially temporary)
ASTContext. For example, the expression parser creates a temporary ASTContext
for parsing the current expression.
The problem with the recursion is however that if we somehow get a cycle into
our mapping, then the ASTImporterDelegate will just infinite recurse. As the
infinite recursion usually happens after the cycle was already created in a code
path such as completing a type, the crash backtraces we get for these bugs are
not very useful. However having the backtrace where the faulty map entry is
created usually makes the code trivial to fix (as there should be some rogue
CopyType call or something similar nearby. See for example D96366).
This patch tries to make these issues easier to track down by putting a bunch of
sanity asserts in the code that fills out the map. All the asserts are just
checking that there is no direct cycle (ASTContext maps to itself) when updating
the origin tracking map.
The assert in the ASTImportDelegate constructor is an `lldbassert` (which also
is getting checked in release builds with disabled asserts) as the code path
there is pretty cold and we can reliably detect a rogue CopyType call from
there.
I also had to update some code in
`ClangASTImporter::ASTImporterDelegate::Imported`. This code already had a
safety check for creating a cycle in the origin tracking map, but it still
constructed an ASTImporter while checking for the cycle (by requesting a
delegate via `GetDelegate` and passing two identical ASTContexts which looks
like a rogue CopyType call to the checks).
Reviewed By: shafik
Differential Revision: https://reviews.llvm.org/D97300
The ASTImporter has an `Imported(From, To)` callback that notifies subclasses
that a declaration has been imported in some way. LLDB uses this in the
`CompleteTagDeclsScope` to see which records have been imported into the scratch
context. If the record was declared inside the expression, then the
`CompleteTagDeclsScope` will forcibly import the full definition of that record
to the scratch context so that the expression AST can safely be disposed later
(otherwise we might end up going back to the deleted AST to complete the
minimally imported record). The way this is implemented is that there is a list
of decls that need to be imported (`m_decls_to_complete`) and we keep completing
the declarations inside that list until the list is empty. Every `To` Decl we
get via the `Imported` callback will be added to the list of Decls to be
completed.
There are some situations where the ASTImporter will actually give us two
`Imported` calls with the same `To` Decl. One way where this happens is if the
ASTImporter decides to merge an imported definition into an already imported
one. Another way is that the ASTImporter just happens to get two calls to
`ASTImporter::Import` for the same Decl. This for example happens when importing
the DeclContext of a Decl requires importing the Decl itself, such as when
importing a RecordDecl that was declared inside a function.
The bug addressed in this patch is that when we end up getting two `Imported`
calls for the same `To` Decl, then we would crash in the
`CompleteTagDeclsScope`. That's because the first time we complete the Decl we
remove the Origin tracking information (that maps the Decl back to from where it
came from). The next time we try to complete the same `To` Decl the Origin
tracking information is gone and we hit the `to_context_md->getOrigin(decl).ctx
== m_src_ctx` assert (`getOrigin(decl).ctx` is a nullptr the second time as the
Origin was deleted).
This is actually a regression coming from D72495. Before D72495
`m_decls_to_complete` was actually a set so every declaration in there could
only be queued once to be completed. The set was changed to a vector to make the
iteration over it deterministic, but that also causes that we now potentially
end up trying to complete a Decl twice.
This patch essentially just reverts D72495 and makes the `CompleteTagDeclsScope`
use a SetVector for the list of declarations to be completed. The SetVector
should filter out the duplicates (as the original `set` did) and also ensure that
the completion order is deterministic. I actually couldn't find any way to cause
LLDB to reproduce this bug by merging declarations (this would require that we
for example declare two namespaces in a non-top-level expression which isn't
possible). But the bug reproduces very easily by just declaring a class in an
expression, so that's what the test is doing.
Reviewed By: shafik
Differential Revision: https://reviews.llvm.org/D85648
The search for the complete class definition can also produce entries
which are not of the expected type. This can happen for instance when
there is a function with the same name as the class we're looking up
(which means that the class needs to be disambiguated with the
struct/class tag in most contexts).
Previously we were just picking the first Decl that the lookup returned,
which later caused crashes or assertion failures if it was not of the
correct type. This patch changes that to search for an entry of the
correct type.
Differential Revision: https://reviews.llvm.org/D85904
Summary:
This patch adds support for evaluation of expressions referring to types
which were compiled in -flimit-debug-info (a.k.a -fno-standalone-debug)
in clang. In this mode it's possible that the debug information needed
to fully describe a c++ type is not present in a single shared library
-- for example debug info for a base class or a member of a type can
only be found in another shared library. This situation is not
currently handled well within lldb as we are limited to searching within
a single shared library (lldb_private::Module) when searching for the
definition of these types.
The way that this patch gets around this limitation is by doing the
search at a later stage -- during the construction of the expression ast
context. This works by having the parser (currently SymbolFileDWARF, but
a similar approach is probably needed for PDBs too) mark a type as
"forcefully completed". What this means is that the parser has marked
the type as "complete" in the module ast context (as this is necessary
to e.g. derive classes from it), but its definition is not really there.
This is done via a new field on the ClangASTMetadata struct.
Later, when we are importing such a type into the expression ast, we
check this flag. If the flag is set, we try to find a better definition
for the type in other shared libraries. We do this by initiating a
new lookup for the "forcefully completed" classes, which then imports the
type from a module with a full definition.
This patch only implements this handling for base classes, but other
cases (members, array element types, etc.). The changes for that should
be fairly simple and mostly revolve around marking these types as
"forcefully completed" at an approriate time -- the importing logic is
generic already.
Another aspect, which is also not handled by this patch is viewing these
types via the "frame variable" command. This does not use the AST
importer and so it will need to handle these types on its own -- that
will be the subject of another patch.
Differential Revision: https://reviews.llvm.org/D81561
Types that came from a Clang module are nested in DW_TAG_module tags
in DWARF. This patch recreates the Clang module hierarchy in LLDB and
1;95;0csets the owning module information accordingly. My primary motivation
is to facilitate looking up per-module APINotes for individual
declarations, but this likely also has other applications.
This reapplies the previously reverted commit, but without support for
ClassTemplateSpecializations, which I'm going to look into separately.
rdar://problem/59634380
Differential Revision: https://reviews.llvm.org/D75488
Types that came from a Clang module are nested in DW_TAG_module tags
in DWARF. This patch recreates the Clang module hierarchy in LLDB and
sets the owning module information accordingly. My primary motivation
is to facilitate looking up per-module APINotes for individual
declarations, but this likely also has other applications.
rdar://problem/59634380
Differential Revision: https://reviews.llvm.org/D75488
Summary:
D73024 seems to have fixed one set crash, but it introduced another.
Namely, if a class contains a covariant method returning itself, the
logic in MaybeCompleteReturnType could cause us to attempt a recursive
import, which would result in an assertion failure in
clang::DeclContext::removeDecl.
For some reason, this only manifested itself if the class contained at
least two member variables, and the class itself was imported as a
result of a recursive covariant import.
This patch fixes the crash by not attempting to import classes which are
already completed in MaybeCompleteReturnType. However, it's not clear to
me if this is the right fix, or if this should be handled automatically
by functions lower in the stack.
Reviewers: teemperor, shafik
Subscribers: lldb-commits
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D76840
Summary:
This change represents the move of ClangASTImporter, ClangASTMetadata,
ClangExternalASTSourceCallbacks, ClangUtil, CxxModuleHandler, and
TypeSystemClang from lldbSource to lldbPluginExpressionParserClang.h
This explicitly removes knowledge of clang internals from lldbSymbol,
moving towards a more generic core implementation of lldb.
Reviewers: JDevlieghere, davide, aprantl, teemperor, clayborg, labath, jingham, shafik
Subscribers: emaste, mgorny, arphaman, jfb, usaxena95, lldb-commits
Tags: #lldb
Differential Revision: https://reviews.llvm.org/D73661
Raphael Isemann