[Lldb-commits] [lldb] [lldb] Convert file address to load address when reading memory for DW_OP_piece (PR #116411)

[via lldb-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-debuginfo

Author: Ilia Kuklin (kuilpd)

<details>
<summary>Changes</summary>

When parsing an optimized value and reading a piece from a file address, LLDB tries to read the data from memory using that address.
This patch converts file address to load address before reading the memory.

Fixes #<!-- -->111313 #<!-- -->97484

---
Full diff: https://github.com/llvm/llvm-project/pull/116411.diff


2 Files Affected:

- (modified) lldb/source/Expression/DWARFExpression.cpp (+16-3) 
- (added) lldb/test/Shell/SymbolFile/DWARF/DW_OP_piece-O3.c (+23) 


``````````diff
diff --git a/lldb/source/Expression/DWARFExpression.cpp b/lldb/source/Expression/DWARFExpression.cpp
index f92f25ed342a9c..a7126b25c1cc38 100644
--- a/lldb/source/Expression/DWARFExpression.cpp
+++ b/lldb/source/Expression/DWARFExpression.cpp
@@ -1853,12 +1853,25 @@ llvm::Expected<Value> DWARFExpression::Evaluate(
           const Value::ValueType curr_piece_source_value_type =
               curr_piece_source_value.GetValueType();
           Scalar &scalar = curr_piece_source_value.GetScalar();
-          const lldb::addr_t addr = scalar.ULongLong(LLDB_INVALID_ADDRESS);
+          lldb::addr_t addr = scalar.ULongLong(LLDB_INVALID_ADDRESS);
           switch (curr_piece_source_value_type) {
           case Value::ValueType::Invalid:
             return llvm::createStringError("invalid value type");
-          case Value::ValueType::LoadAddress:
-          case Value::ValueType::FileAddress: {
+          case Value::ValueType::FileAddress:
+            if (target) {
+              curr_piece_source_value.ConvertToLoadAddress(module_sp.get(),
+                                                           target);
+              addr = scalar.ULongLong(LLDB_INVALID_ADDRESS);
+            } else {
+              return llvm::createStringError(
+                  "unable to convert file address 0x%" PRIx64
+                  " to load address "
+                  "for DW_OP_piece(%" PRIu64 "): "
+                  "no target available",
+                  addr, piece_byte_size);
+            }
+            [[fallthrough]];
+          case Value::ValueType::LoadAddress: {
             if (target) {
               if (curr_piece.ResizeData(piece_byte_size) == piece_byte_size) {
                 if (target->ReadMemory(addr, curr_piece.GetBuffer().GetBytes(),
diff --git a/lldb/test/Shell/SymbolFile/DWARF/DW_OP_piece-O3.c b/lldb/test/Shell/SymbolFile/DWARF/DW_OP_piece-O3.c
new file mode 100644
index 00000000000000..d31250426dc112
--- /dev/null
+++ b/lldb/test/Shell/SymbolFile/DWARF/DW_OP_piece-O3.c
@@ -0,0 +1,23 @@
+// Check that optimized with -O3 values that have a file address can be read
+// DWARF info:
+// 0x00000023:   DW_TAG_variable
+//                 DW_AT_name      ("array")
+//                 DW_AT_type      (0x00000032 "char[5]")
+//                 DW_AT_location  (DW_OP_piece 0x2, DW_OP_addrx 0x0, DW_OP_piece 0x1)
+
+// RUN: %clang_host -O3 -gdwarf %s -o %t
+// RUN: %lldb %t \
+// RUN:   -o "b 22" \
+// RUN:   -o "r" \
+// RUN:   -o "p/x array[2]" \
+// RUN:   -b | FileCheck %s
+//
+// CHECK: (lldb) p/x array[2]
+// CHECK: (char) 0x03
+
+static char array[5] = {0, 1, 2, 3, 4};
+
+int main(void) {
+  array[2]++;
+  return 0;
+}
\ No newline at end of file

``````````

</details>


https://github.com/llvm/llvm-project/pull/116411