Summary:
In case of Dwo, DIERef stores a compile unit offset in the main object file, and not in the dwo.
The implementation of SymbolFileDWARFDwo::GetDIE inherited from SymbolFileDWARF tried to lookup
the compilation unit in the DWO based on the main object file offset (and failed). I change the
implementation to verify the DIERef indeed references compile unit belonging to this dwo and then
lookup the die based on the die offset alone.
Includes a couple of fixes for mismatched struct/class tags.
Reviewers: tberghammer, clayborg
Subscribers: lldb-commits
Differential Revision: http://reviews.llvm.org/D18646
llvm-svn: 265011
1 - DWARF in .o files with debug map in executable: we would place the compile unit index in the upper 32 bits of the 64 bit value and the lower 32 bits would be the DIE offset
2 - DWO: we would place the compile unit offset in the upper 32 bits of the 64 bit value and the lower 32 bits would be the DIE offset
There was a mixing and matching of this and it wasn't done consistently.
Major changes include:
The DIERef constructor that takes a lldb::user_id_t now requires a SymbolFileDWARF:
DIERef(lldb::user_id_t uid, SymbolFileDWARF *dwarf)
It is needed so that it can be decoded correctly. If it is DWARF in .o files with debug map in executable, then we get the right compile unit from the SymbolFileDWARFDebugMap, otherwise, we use the compile unit offset and DIE offset for DWO or normal DWARF.
The function:
lldb::user_id_t DIERef::GetUID() const;
Now becomes
lldb::user_id_t DIERef::GetUID(SymbolFileDWARF *dwarf) const;
Again, we need the DWARF file to encode it correctly.
This removes the need for "lldb::user_id_t SymbolFileDWARF::MakeUserID() const" and for bool SymbolFileDWARF::UserIDMatches (lldb::user_id_t uid) const". There were also many places were doing things inneficiently like:
1 - encode a dw_offset_t into a lldb::user_id_t
2 - call the public SymbolFile interface to resolve types using the lldb::user_id_t
3 - This would then decode the lldb::user_id_t into a DIERef, and then try to find that type.
There are many places that are now doing this more efficiently by storing DW_AT_type form values as DWARFFormValue objects and then making a DIERef from them and directly calling the underlying function to resolve the lldb_private::Type, lldb_private::CompilerType, lldb_private::CompilerDecl, lldb_private::CompilerDeclContext.
If there are any regressions in DWARF with DWO, we will need to fix any issues that arise since the original patch wasn't functional for the much more widely used DWARF in .o files with debug map.
<rdar://problem/25200976>
llvm-svn: 264909
llvm::DenseSet<lldb_private::SymbolFile *> &searched_symbol_files
Each time a SymbolFile::FindTypes() is called, it needs to check the searched_symbol_files list to make sure it hasn't already been asked to find the type and return immediately if it has been checked. This will stop circular dependencies from also crashing LLDB during type queries.
This has proven to be an issue when debugging large applications on MacOSX that use DWARF in .o files.
<rdar://problem/24581488>
llvm-svn: 260434
Summary:
DWARF 5 proposes a reinvented .debug_macro section. This change follows
that spec.
Currently, only GCC produces the .debug_macro section and hence
the added test is annottated with expectedFailureClang.
Reviewers: spyffe, clayborg, tberghammer
Subscribers: lldb-commits
Differential Revision: http://reviews.llvm.org/D15437
llvm-svn: 255729
Summary:
In bug 24074, the type information is not shown
correctly. This commit includes the following -
-> Changes for displaying correct type based on
current lexical scope for the command "image
lookup -t"
-> The corresponding testcase.
-> This patch was reverted due to segfaults in
FreeBSD and Mac, I fixed the problems for both now.
Reviewers: emaste, granata.enrico, jingham, clayborg
Differential Revision: http://reviews.llvm.org/D13290
llvm-svn: 249673
Summary:
In bug 24074, the type information is not shown
correctly. This commit includes the following -
-> Changes for displaying correct type based on
current lexical scope for the command "image
lookup -t"
-> The corresponding testcase.
Reviewers: jingham, ovyalov, spyffe, richard.mitton, clayborg
Differential Revision: http://reviews.llvm.org/D12404
llvm-svn: 248366
Summary:
With the recent changes to separate clang from the core structures
of LLDB, many inclusions of clang headers can be removed.
Reviewers: clayborg
Subscribers: lldb-commits
Differential Revision: http://reviews.llvm.org/D12954
llvm-svn: 248004
class DWARFASTParser
{
public:
virtual ~DWARFASTParser() {}
virtual lldb::TypeSP
ParseTypeFromDWARF (const lldb_private::SymbolContext& sc,
const DWARFDIE &die,
lldb_private::Log *log,
bool *type_is_new_ptr) = 0;
virtual lldb_private::Function *
ParseFunctionFromDWARF (const lldb_private::SymbolContext& sc,
const DWARFDIE &die) = 0;
virtual bool
CompleteTypeFromDWARF (const DWARFDIE &die,
lldb_private::Type *type,
lldb_private::CompilerType &clang_type) = 0;
virtual lldb_private::CompilerDeclContext
GetDeclContextForUIDFromDWARF (const DWARFDIE &die) = 0;
virtual lldb_private::CompilerDeclContext
GetDeclContextContainingUIDFromDWARF (const DWARFDIE &die) = 0;
};
We have one subclass named DWARFASTParserClang that implements all of the clang specific AST type parsing. This keeps all DWARF parsing in the DWARF plug-in. Moved all of the DWARF parsing code that was in ClangASTContext over into DWARFASTParserClang.
lldb_private::TypeSystem classes no longer have any DWARF parsing functions in them, but they can hand out a DWARFASTParser:
virtual DWARFASTParser *
GetDWARFParser ()
{
return nullptr;
}
This keeps things clean and makes for easy merging when we have different AST's for different languages.
llvm-svn: 246242
Added a new class called DWARFDIE that contains a DWARFCompileUnit and DWARFDebugInfoEntry so that these items always stay together.
There were many places where we just handed out DWARFDebugInfoEntry pointers and then use them with a compile unit that may or may not be the correct one. Clients outside of DWARFCompileUnit and DWARFDebugInfoEntry should all be dealing with DWARFDIE instances instead of playing with DWARFCompileUnit/DWARFDebugInfoEntry pairs manually.
This paves to the way for some modifications that are coming for DWO.
llvm-svn: 246100
Create a new "lldb_private::CompilerDeclContext" class that will replace all direct uses of "clang::DeclContext" when used in compiler agnostic code, yet still allow for conversion to clang::DeclContext subclasses by clang specific code. This completes the abstraction of type parsing by removing all "clang::" references from the SymbolFileDWARF. The new "lldb_private::CompilerDeclContext" class abstracts decl contexts found in compiler type systems so they can be used in internal API calls. The TypeSystem is required to support CompilerDeclContexts with new pure virtual functions that start with "DeclContext" in the member function names. Converted all code that used lldb_private::ClangNamespaceDecl over to use the new CompilerDeclContext class and removed the ClangNamespaceDecl.cpp and ClangNamespaceDecl.h files.
Removed direct use of clang APIs from SBType and now use the abstract type systems to correctly explore types.
Bulk renames for things that used to return a ClangASTType which is now CompilerType:
"Type::GetClangFullType()" to "Type::GetFullCompilerType()"
"Type::GetClangLayoutType()" to "Type::GetLayoutCompilerType()"
"Type::GetClangForwardType()" to "Type::GetForwardCompilerType()"
"Value::GetClangType()" to "Value::GetCompilerType()"
"Value::SetClangType (const CompilerType &)" to "Value::SetCompilerType (const CompilerType &)"
"ValueObject::GetClangType ()" to "ValueObject::GetCompilerType()"
many more renames that are similar.
llvm-svn: 245905
Another step towards isolating all language/AST specific code into the files to further abstract specific implementations of parsing types for a given language.
llvm-svn: 245090
This is more preparation for multiple different kinds of types from different compilers (clang, Pascal, Go, RenderScript, Swift, etc).
llvm-svn: 244689
module-loading support for the expression parser.
- It adds support for auto-loading modules referred
to by a compile unit. These references are
currently in the form of empty translation units.
This functionality is gated by the setting
target.auto-import-clang-modules (boolean) = false
- It improves and corrects support for loading
macros from modules, currently by textually
pasting all #defines into the user's expression.
The improvements center around including only those
modules that are relevant to the current context -
hand-loaded modules and the modules that are imported
from the current compile unit.
- It adds an "opt-in" mechanism for all of this
functionality. Modules have to be explicitly
imported (via @import) or auto-loaded (by enabling
the above setting) to enable any of this
functionality.
It also adds support to the compile unit and symbol
file code to deal with empty translation units that
indicate module imports, and plumbs this through to
the CompileUnit interface.
Finally, it makes the following changes to the test
suite:
- It adds a testcase that verifies that modules are
automatically loaded when the appropriate setting
is enabled (lang/objc/modules-auto-import); and
- It modifies lanb/objc/modules-incomplete to test
the case where a module #undefs something that is
#defined in another module.
<rdar://problem/20299554>
llvm-svn: 235313
files. Before we'd give up if we found a .o that doesn't have
DWARF associated with it; now we iterate through them all.
Also made this iteration a higher-order function so that people
don't have to remember to do this right.
<rdar://problem/20261196>
llvm-svn: 233838
Since ClangASTSource::layoutRecordType() was overriding a virtual
function in the base, this was inadvertently causing a new method
to be introduced rather than an override. To fix this all method
signatures are changed back to taking DenseMaps, and the `override`
keyword is added to make sure this type of error doesn't happen
again.
To keep the original fix intact, which is that fields and bases
must be added in offset order, the ImportOffsetMap() function
now copies the DenseMap into a vector and then sorts the vector
on the value type (e.g. the offset) before iterating over the
sorted vector and inserting the items.
llvm-svn: 233099
Prior to this patch, we would try to synthesize class types by
iterating over a DenseMap of FieldDecls and adding each one to
a CXXRecordDecl. Since a DenseMap doesn't provide a deterministic
ordering of the elements, this would not add the fields in
FieldOffset order, but rather in some random order determined by
the memory layout of the DenseMap.
This patch fixes the issue by changing DenseMaps to vectors. The
ability to lookup a value in the DenseMap was hardly being used,
and where it is sufficient to do a vector lookup.
Differential Revision: http://reviews.llvm.org/D8512
llvm-svn: 233090
A long time ago we start with clang types that were created by the symbol files and there were many functions in lldb_private::ClangASTContext that helped. Later we create ClangASTType which contains a clang::ASTContext and an opauque QualType, but we didn't switch over to fully using it. There were a lot of places where we would pass around a raw clang_type_t and also pass along a clang::ASTContext separately. This left room for error.
This checkin change all type code over to use ClangASTType everywhere and I cleaned up the interfaces quite a bit. Any code that was in ClangASTContext that was type related, was moved over into ClangASTType. All code that used these types was switched over to use all of the new goodness.
llvm-svn: 186130
//------------------------------------------------------------------
/// Get all types matching \a type_mask from debug info in this
/// module.
///
/// @param[in] type_mask
/// A bitfield that consists of one or more bits logically OR'ed
/// together from the lldb::TypeClass enumeration. This allows
/// you to request only structure types, or only class, struct
/// and union types. Passing in lldb::eTypeClassAny will return
/// all types found in the debug information for this module.
///
/// @return
/// A list of types in this module that match \a type_mask
//------------------------------------------------------------------
lldb::SBTypeList
SBModule::GetTypes (uint32_t type_mask)
//------------------------------------------------------------------
/// Get all types matching \a type_mask from debug info in this
/// compile unit.
///
/// @param[in] type_mask
/// A bitfield that consists of one or more bits logically OR'ed
/// together from the lldb::TypeClass enumeration. This allows
/// you to request only structure types, or only class, struct
/// and union types. Passing in lldb::eTypeClassAny will return
/// all types found in the debug information for this compile
/// unit.
///
/// @return
/// A list of types in this compile unit that match \a type_mask
//------------------------------------------------------------------
lldb::SBTypeList
SBCompileUnit::GetTypes (uint32_t type_mask = lldb::eTypeClassAny);
This lets you request types by filling out a mask that contains one or more bits from the lldb::TypeClass enumerations, so you can only get the types you really want.
llvm-svn: 184251
<rdar://problem/13594769>
Main changes in this patch include:
- cleanup plug-in interface and use ConstStrings for plug-in names
- Modfiied the BSD Archive plug-in to be able to pick out the correct .o file when .a files contain multiple .o files with the same name by using the timestamp
- Modified SymbolFileDWARFDebugMap to properly verify the timestamp on .o files it loads to ensure we don't load updated .o files and cause problems when debugging
The plug-in interface changes:
Modified the lldb_private::PluginInterface class that all plug-ins inherit from:
Changed:
virtual const char * GetPluginName() = 0;
To:
virtual ConstString GetPluginName() = 0;
Removed:
virtual const char * GetShortPluginName() = 0;
- Fixed up all plug-in to adhere to the new interface and to return lldb_private::ConstString values for the plug-in names.
- Fixed all plug-ins to return simple names with no prefixes. Some plug-ins had prefixes and most ones didn't, so now they all don't have prefixed names, just simple names like "linux", "gdb-remote", etc.
llvm-svn: 181631
DWARF with .o files now uses 40-60% less memory!
Big fixes include:
- Change line table internal representation to contain "file addresses". Since each line table is owned by a compile unit that is owned by a module, it makes address translation into lldb_private::Address easy to do when needed.
- Removed linked address members/methods from lldb_private::Section and lldb_private::Address
- lldb_private::LineTable can now relink itself using a FileRangeMap to make it easier to re-link line tables in the future
- Added ObjectFile::ClearSymtab() so that we can get rid of the object file symbol tables after we parse them once since they are not needed and kept memory allocated for no reason
- Moved the m_sections_ap (std::auto_ptr to section list) and m_symtab_ap (std::auto_ptr to the lldb_private::Symtab) out of each of the ObjectFile subclasses and put it into lldb_private::ObjectFile.
- Changed how the debug map is parsed and stored to be able to:
- Lazily parse the debug map for each object file
- not require the address map for a .o file until debug information is linked for a .o file
llvm-svn: 176454
The first part of the fix for having LLDB handle LTO debugging when the DWARF is in the .o files. This part separates the object file's modules into a separate cache map that maps unique C strings for the N_OSO path to the ModuleSP since one object file might be mentioned more than once in LTO binaries.
llvm-svn: 174476
Make breakpoint setting by file and line much more efficient by only looking for inlined breakpoint locations if we are setting a breakpoint in anything but a source implementation file. Implementing this complex for a many reasons. Turns out that parsing compile units lazily had some issues with respect to how we need to do things with DWARF in .o files. So the fixes in the checkin for this makes these changes:
- Add a new setting called "target.inline-breakpoint-strategy" which can be set to "never", "always", or "headers". "never" will never try and set any inlined breakpoints (fastest). "always" always looks for inlined breakpoint locations (slowest, but most accurate). "headers", which is the default setting, will only look for inlined breakpoint locations if the breakpoint is set in what are consudered to be header files, which is realy defined as "not in an implementation source file".
- modify the breakpoint setting by file and line to check the current "target.inline-breakpoint-strategy" setting and act accordingly
- Modify compile units to be able to get their language and other info lazily. This allows us to create compile units from the debug map and not have to fill all of the details in, and then lazily discover this information as we go on debuggging. This is needed to avoid parsing all .o files when setting breakpoints in implementation only files (no inlines). Otherwise we would need to parse the .o file, the object file (mach-o in our case) and the symbol file (DWARF in the object file) just to see what the compile unit was.
- modify the "SymbolFileDWARFDebugMap" to subclass lldb_private::Module so that the virtual "GetObjectFile()" and "GetSymbolVendor()" functions can be intercepted when the .o file contenst are later lazilly needed. Prior to this fix, when we first instantiated the "SymbolFileDWARFDebugMap" class, we would also make modules, object files and symbol files for every .o file in the debug map because we needed to fix up the sections in the .o files with information that is in the executable debug map. Now we lazily do this in the DebugMapModule::GetObjectFile()
Cleaned up header includes a bit as well.
llvm-svn: 162860
Fixed an issue that would happen when using debug map with DWARF in the .o files where we wouldn't ever track down the actual definition for a type when things were in namespaces. We now serialize the decl context information into an intermediate format which allows us to track down the correct definition for a type regardless of which DWARF symbol file it comes from. We do this by creating a "DWARFDeclContext" object that contains the DW_TAG + name for each item in a decl context which we can then use to veto potential accelerator table matches. For example, the accelerator tables store the basename of the type, so if you have "std::vector<int>", we would end up with an accelerator table entry for the type that contained "vector<int>", which we would then search for using a DWARFDeclContext object that contained:
[0] DW_TAG_class_type "vector<int>"
[1] DW_TAG_namespace "std"
This is currently used to track down forward declarations for things like "class a:🅱️:Foo;".
llvm-svn: 155488
indicate whether inline functions are desired.
This allows the expression parser, for instance,
to filter out inlined functions when looking for
functions it can call.
llvm-svn: 150279
due to RTTI worries since llvm and clang don't use RTTI, but I was able to
switch back with no issues as far as I can tell. Once the RTTI issue wasn't
an issue, we were looking for a way to properly track weak pointers to objects
to solve some of the threading issues we have been running into which naturally
led us back to std::tr1::weak_ptr. We also wanted the ability to make a shared
pointer from just a pointer, which is also easily solved using the
std::tr1::enable_shared_from_this class.
The main reason for this move back is so we can start properly having weak
references to objects. Currently a lldb_private::Thread class has a refrence
to its parent lldb_private::Process. This doesn't work well when we now hand
out a SBThread object that contains a shared pointer to a lldb_private::Thread
as this SBThread can be held onto by external clients and if they end up
using one of these objects we can easily crash.
So the next task is to start adopting std::tr1::weak_ptr where ever it makes
sense which we can do with lldb_private::Debugger, lldb_private::Target,
lldb_private::Process, lldb_private::Thread, lldb_private::StackFrame, and
many more objects now that they are no longer using intrusive ref counted
pointer objects (you can't do std::tr1::weak_ptr functionality with intrusive
pointers).
llvm-svn: 149207
will ask ExternalASTSource objects to help laying out a type. This is needed
because the DWARF typically doesn't contain alignement or packing attribute
values, and we need to be able to match up types that the compiler uses
in expressions.
llvm-svn: 149160
Fix DWARF parsing issue we can run into when using llvm-gcc based dSYM files.
Also fix the parsing of objective C built-in types (Class, id and SEL) so
they don't parse more information that is not needed due to the way they
are represented in DWARF.
llvm-svn: 148016
class. The thing with Objective C classes is the debug info might have a
definition that isn't just a forward decl, but it is incomplete. So we need to
look and see if we can find the complete definition and avoid recursing a lot
due to the fact that our accelerator tables will have many versions of the
type, but only one complete one. We might not also have the complete type
and we need to deal with this correctly.
llvm-svn: 145759
Objective-C, making symbol lookups for various raw
Objective-C symbols work correctly. The IR interpreter
makes these lookups because Clang has emitted raw
symbol references for ivars and classes.
Also improved performance in SymbolFiles, caching the
result of asking for SymbolFile abilities.
llvm-svn: 145758
process IDs, and thread IDs, but was mainly needed for for the UserID's for
Types so that DWARF with debug map can work flawlessly. With DWARF in .o files
the type ID was the DIE offset in the DWARF for the .o file which is not
unique across all .o files, so now the SymbolFileDWARFDebugMap class will
make the .o file index part (the high 32 bits) of the unique type identifier
so it can uniquely identify the types.
llvm-svn: 142534
down through Module and SymbolVendor into SymbolFile.
Added checks to SymbolFileDWARF that restrict symbol
searches when a namespace is passed in.
llvm-svn: 141847
an interface to a local or remote debugging platform. By default each host OS
that supports LLDB should be registering a "default" platform that will be
used unless a new platform is selected. Platforms are responsible for things
such as:
- getting process information by name or by processs ID
- finding platform files. This is useful for remote debugging where there is
an SDK with files that might already or need to be cached for debug access.
- getting a list of platform supported architectures in the exact order they
should be selected. This helps the native x86 platform on MacOSX select the
correct x86_64/i386 slice from universal binaries.
- Connect to remote platforms for remote debugging
- Resolving an executable including finding an executable inside platform
specific bundles (macosx uses .app bundles that contain files) and also
selecting the appropriate slice of universal files for a given platform.
So by default there is always a local platform, but remote platforms can be
connected to. I will soon be adding a new "platform" command that will support
the following commands:
(lldb) platform connect --name machine1 macosx connect://host:port
Connected to "machine1" platform.
(lldb) platform disconnect macosx
This allows LLDB to be well setup to do remote debugging and also once
connected process listing and finding for things like:
(lldb) process attach --name x<TAB>
The currently selected platform plug-in can now auto complete any available
processes that start with "x". The responsibilities for the platform plug-in
will soon grow and expand.
llvm-svn: 127286
ArchDefaultUnwindPlan plug-in interfaces are now cached per architecture
instead of being leaked for every frame.
Split the ArchDefaultUnwindPlan_x86 into ArchDefaultUnwindPlan_x86_64 and
ArchDefaultUnwindPlan_i386 interfaces.
There were sporadic crashes that were due to something leaking or being
destroyed when doing stack crawls. This patch should clear up these issues.
llvm-svn: 125541
the way LLDB lazily gets complete definitions for types within the debug info.
When we run across a class/struct/union definition in the DWARF, we will only
parse the full definition if we need to. This works fine for top level types
that are assigned directly to variables and arguments, but when we have a
variable with a class, lets say "A" for this example, that has a member:
"B *m_b". Initially we don't need to hunt down a definition for this class
unless we are ever asked to do something with it ("expr m_b->getDecl()" for
example). With my previous approach to lazy type completion, we would be able
to take a "A *a" and get a complete type for it, but we wouldn't be able to
then do an "a->m_b->getDecl()" unless we always expanded all types within a
class prior to handing out the type. Expanding everything is very costly and
it would be great if there were a better way.
A few months ago I worked with the llvm/clang folks to have the
ExternalASTSource class be able to complete classes if there weren't completed
yet:
class ExternalASTSource {
....
virtual void
CompleteType (clang::TagDecl *Tag);
virtual void
CompleteType (clang::ObjCInterfaceDecl *Class);
};
This was great, because we can now have the class that is producing the AST
(SymbolFileDWARF and SymbolFileDWARFDebugMap) sign up as external AST sources
and the object that creates the forward declaration types can now also
complete them anywhere within the clang type system.
This patch makes a few major changes:
- lldb_private::Module classes now own the AST context. Previously the TypeList
objects did.
- The DWARF parsers now sign up as an external AST sources so they can complete
types.
- All of the pure clang type system wrapper code we have in LLDB (ClangASTContext,
ClangASTType, and more) can now be iterating through children of any type,
and if a class/union/struct type (clang::RecordType or ObjC interface)
is found that is incomplete, we can ask the AST to get the definition.
- The SymbolFileDWARFDebugMap class now will create and use a single AST that
all child SymbolFileDWARF classes will share (much like what happens when
we have a complete linked DWARF for an executable).
We will need to modify some of the ClangUserExpression code to take more
advantage of this completion ability in the near future. Meanwhile we should
be better off now that we can be accessing any children of variables through
pointers and always be able to resolve the clang type if needed.
llvm-svn: 123613
cases when getting the clang type:
- need only a forward declaration
- need a clang type that can be used for layout (members and args/return types)
- need a full clang type
This allows us to partially parse the clang types and be as lazy as possible.
The first case is when we just need to declare a type and we will complete it
later. The forward declaration happens only for class/union/structs and enums.
The layout type allows us to resolve the full clang type _except_ if we have
any modifiers on a pointer or reference (both R and L value). In this case
when we are adding members or function args or return types, we only need to
know how the type will be laid out and we can defer completing the pointee
type until we later need it. The last type means we need a full definition for
the clang type.
Did some renaming of some enumerations to get rid of the old "DC" prefix (which
stands for DebugCore which is no longer around).
Modified the clang namespace support to be almost ready to be fed to the
expression parser. I made a new ClangNamespaceDecl class that can carry around
the AST and the namespace decl so we can copy it into the expression AST. I
modified the symbol vendor and symbol file plug-ins to use this new class.
llvm-svn: 118976
namespaces by name given an optional symbol context. I might end up
dressing up the "clang::NamespaceDecl" into a lldb_private::Namespace
class if we need to do more than is currenlty required of namespaces.
Currently we only need to be able to lookup a namespace by name when
parsing expressions, so I kept it simple for now. The idea here is
even though we are passing around a "clang::NamespaceDecl *", that
we always have it be an opaque pointer (it is forward declared inside
of "lldb/Core/ClangForward.h") and we only use clang::NamespaceDecl
implementations inside of ClangASTContext, or ClangASTType when we need
to extract information from the namespace decl object.
llvm-svn: 118737
Greg Clayton