[lldb] Enable using out-of-tree dwps

[alexander-shaposhnikov]

Summary

Previously LLDB required the DWP file to be located next to the executable file
(see the code in SymbolFileDWARF::GetDwpSymbolFile).
This diff uses the helper function Symbols::LocateExecutableSymbolFile
to search for DWP files in the standard locations for debug symbols.

Test plan:

Build a toy test example
main.cpp
clang -gsplit-dwarf -g -O0 main.cpp -o main.exe
llvm-dwp -e main.exe -o main.exe.dwp
mkdir -p debug_symbols
mv main.exe.dwp debug_symbols/main.exe.dwp
rm -f main.dwo

Run lldb:
lldb
settings set target.debug-file-search-paths ./debug_symbols
file ./main.exe
br set --name f
r

Check that debugging works
(setting breakpoints, printing local variables (this was not working before))

[alexander-shaposhnikov]

Ping

[tberghammer]

source/Host/common/Symbols.cpp

288–294

What do you think about adding a new argument to Symbols::LocateExecutableSymbolFile (with a potential default value) to specify if we want to check the UUID and then move this logic to the place where we are looking for the dwp file? I think that would make dwp specific logic more concise in one place.

[clayborg]

source/Host/common/Symbols.cpp

288–294

An easier fix is to clear the UUID field from in "module_spec" _before_ you call this function. The module spec can be filled in as much as is needed, so either clear the UUID in module_spec if it is set, or just don't set it. This function should ignore the UUID comparison if the UUID field is not valid in module_spec, so if it isn't doing this, then it should

[clayborg]

(sorry for the delay, I was out on vacation for a week)

[alexander-shaposhnikov]

Ignore the UUID comparison if the UUID field is not valid (in this case the interface seems to be a bit cleaner (module_spec is the single source of truth (without extra parameters))

[clayborg]

Looks good.

[tberghammer]

Looks good. Thanks for fixing it.

source/Host/common/Symbols.cpp

for (size_t idx = 0; idx < num_directories; ++idx) {
           lldb_private::ModuleSpecList specs;
           const size_t num_specs =
               ObjectFile::GetModuleSpecifications(file_spec, 0, 0, specs);
           assert(num_specs <= 1 &&
                  "Symbol Vendor supports only a single architecture");
           if (num_specs == 1) {
             ModuleSpec mspec;
             if (specs.GetModuleSpecAtIndex(0, mspec)) {
-              if (mspec.GetUUID() == module_uuid)
+              // FIXME: at the moment llvm-dwp doesn't output build ids,
+              // nor does binutils dwp. Thus in the case of DWPs
+              // we skip uuids check. This needs to be fixed
+              // to avoid consistency issues as soon as
+              // llvm-dwp and binutils dwp gain support for build ids.
+              if (file_spec.GetFileNameExtension().GetStringRef() == "dwp" ||
+                  mspec.GetUUID() == module_uuid)
                 return file_spec;
             }
           }
         }
       }
     }
   }
 

source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

 #include "lldb/Utility/RegularExpression.h"
 #include "lldb/Utility/StreamString.h"
 #include "lldb/Utility/Timer.h"
 
 #include "Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.h"
 
 #include "lldb/Host/FileSystem.h"
 #include "lldb/Host/Host.h"
+#include "lldb/Host/Symbols.h"
 
 #include "lldb/Interpreter/OptionValueFileSpecList.h"
 #include "lldb/Interpreter/OptionValueProperties.h"
 
 #include "lldb/Symbol/Block.h"
 #include "lldb/Symbol/ClangASTContext.h"
 #include "lldb/Symbol/ClangUtil.h"
 #include "lldb/Symbol/CompileUnit.h"

 
 DWARFExpression::LocationListFormat
 SymbolFileDWARF::GetLocationListFormat() const {
   return DWARFExpression::RegularLocationList;
 }
 
 SymbolFileDWARFDwp *SymbolFileDWARF::GetDwpSymbolFile() {
   llvm::call_once(m_dwp_symfile_once_flag, [this]() {
-    FileSpec dwp_filespec(m_obj_file->GetFileSpec().GetPath() + ".dwp", false);
+    ModuleSpec module_spec;
+    module_spec.GetFileSpec() = m_obj_file->GetFileSpec();
+    module_spec.GetSymbolFileSpec() =
+        FileSpec(m_obj_file->GetFileSpec().GetPath() + ".dwp", false);
+    FileSpec dwp_filespec = Symbols::LocateExecutableSymbolFile(module_spec);
     if (dwp_filespec.Exists()) {
       m_dwp_symfile = SymbolFileDWARFDwp::Create(GetObjectFile()->GetModule(),
                                                  dwp_filespec);
     }
   });
   return m_dwp_symfile.get();
 }