[lldb] Add a per-CU API to read the SDK (#119022)

The Swift plugin would find this useful.

Author: adrian-prantl

lldb/include/lldb/Target/Platform.h

@@ -473,6 +473,32 @@ class Platform : public PluginInterface {
                       LLVM_PRETTY_FUNCTION, GetName()));
   }
 
+  /// Search CU for the SDK path the CUs was compiled against.
+  ///
+  /// \param[in] unit The CU
+  ///
+  /// \returns A parsed XcodeSDK object if successful, an Error otherwise. 
+  virtual llvm::Expected<XcodeSDK> GetSDKPathFromDebugInfo(CompileUnit &unit) {
+    return llvm::createStringError(
+        llvm::formatv("{0} not implemented for '{1}' platform.",
+                      LLVM_PRETTY_FUNCTION, GetName()));
+  }
+
+  /// Returns the full path of the most appropriate SDK for the
+  /// specified compile unit. This function gets this path by parsing
+  /// debug-info (see \ref `GetSDKPathFromDebugInfo`).
+  ///
+  /// \param[in] unit The CU to scan.
+  ///
+  /// \returns If successful, returns the full path to an
+  ///          Xcode SDK.
+  virtual llvm::Expected<std::string>
+  ResolveSDKPathFromDebugInfo(CompileUnit &unit) {
+    return llvm::createStringError(
+        llvm::formatv("{0} not implemented for '{1}' platform.",
+                      LLVM_PRETTY_FUNCTION, GetName()));
+  }
+
   bool IsHost() const {
     return m_is_host; // Is this the default host platform?
   }

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

@@ -29,6 +29,7 @@
 #include "lldb/Interpreter/OptionValueProperties.h"
 #include "lldb/Interpreter/OptionValueString.h"
 #include "lldb/Interpreter/Options.h"
+#include "lldb/Symbol/CompileUnit.h"
 #include "lldb/Symbol/ObjectFile.h"
 #include "lldb/Symbol/SymbolFile.h"
 #include "lldb/Symbol/SymbolVendor.h"
@@ -1429,3 +1430,39 @@ PlatformDarwin::ResolveSDKPathFromDebugInfo(Module &module) {
 
   return path_or_err->str();
 }
+
+llvm::Expected<XcodeSDK>
+PlatformDarwin::GetSDKPathFromDebugInfo(CompileUnit &unit) {
+  ModuleSP module_sp = unit.CalculateSymbolContextModule();
+  if (!module_sp)
+    return llvm::createStringError("compile unit has no module");
+  SymbolFile *sym_file = module_sp->GetSymbolFile();
+  if (!sym_file)
+    return llvm::createStringError(
+        llvm::formatv("No symbol file available for module '{0}'",
+                      module_sp->GetFileSpec().GetFilename()));
+
+  return sym_file->ParseXcodeSDK(unit);
+}
+
+llvm::Expected<std::string>
+PlatformDarwin::ResolveSDKPathFromDebugInfo(CompileUnit &unit) {
+  auto sdk_or_err = GetSDKPathFromDebugInfo(unit);
+  if (!sdk_or_err)
+    return llvm::createStringError(
+        llvm::inconvertibleErrorCode(),
+        llvm::formatv("Failed to parse SDK path from debug-info: {0}",
+                      llvm::toString(sdk_or_err.takeError())));
+
+  auto sdk = std::move(*sdk_or_err);
+
+  auto path_or_err = HostInfo::GetSDKRoot(HostInfo::SDKOptions{sdk});
+  if (!path_or_err)
+    return llvm::createStringError(
+        llvm::inconvertibleErrorCode(),
+        llvm::formatv("Error while searching for SDK (XcodeSDK '{0}'): {1}",
+                      sdk.GetString(),
+                      llvm::toString(path_or_err.takeError())));
+
+  return path_or_err->str();
+}

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.h

@@ -130,6 +130,11 @@ class PlatformDarwin : public PlatformPOSIX {
   llvm::Expected<std::string>
   ResolveSDKPathFromDebugInfo(Module &module) override;
 
+  llvm::Expected<XcodeSDK> GetSDKPathFromDebugInfo(CompileUnit &unit) override;
+
+  llvm::Expected<std::string>
+  ResolveSDKPathFromDebugInfo(CompileUnit &unit) override;
+
 protected:
   static const char *GetCompatibleArch(ArchSpec::Core core, size_t idx);
 

lldb/unittests/SymbolFile/DWARF/XcodeSDKModuleTests.cpp

@@ -268,6 +268,13 @@ TEST_P(SDKPathParsingMultiparamTests, TestSDKPathFromDebugInfo) {
   EXPECT_EQ(found_mismatch, expect_mismatch);
   EXPECT_EQ(sdk.IsAppleInternalSDK(), expect_internal_sdk);
   EXPECT_NE(sdk.GetString().find(expect_sdk_path_pattern), std::string::npos);
+
+  {
+    auto sdk_or_err =
+        platform_sp->GetSDKPathFromDebugInfo(*dwarf_cu->GetLLDBCompUnit());
+    ASSERT_TRUE(static_cast<bool>(sdk_or_err));
+    EXPECT_EQ(sdk.IsAppleInternalSDK(), expect_internal_sdk);
+  }
 }
 
 SDKPathParsingTestData sdkPathParsingTestCases[] = {