From 24e9e22891ae9bf46d9f80d16ffbe6873b81f284 Mon Sep 17 00:00:00 2001
From: Ryan Mansfield <ryan_mansfield@apple.com>
Date: Tue, 20 Jan 2026 13:01:33 -0500
Subject: [PATCH] Warn when split DWARF files are missing

When analyzing binaries with split DWARF (DW_AT_GNU_dwo_name),
skip missing .dwo files with a warning instead of erroring.

This allows analyzing binaries built on other machines or from
SDKs where .dwo files may not be locally available, while still
alerting the user that the analysis is incomplete.
---
 src/dwarf.cc                                 |  6 ++
 tests/dwarf/debug_info/missing-dwo-file.test | 66 ++++++++++++++++++++
 2 files changed, 72 insertions(+)
 create mode 100644 tests/dwarf/debug_info/missing-dwo-file.test

diff --git a/src/dwarf.cc b/src/dwarf.cc
index 04bca7b..2565703 100644
--- a/src/dwarf.cc
+++ b/src/dwarf.cc
@@ -668,6 +668,12 @@ static void ReadDWARFDebugInfo(dwarf::InfoReader& reader,
 
     std::string dwo_path = ConstructDwoPath(dwo_info);
     if (!dwo_path.empty()) {
+      // Check if DWO file exists before trying to open it
+      if (!std::filesystem::exists(dwo_path)) {
+        fprintf(stderr, "Warning: DWO file not found: %s\n", dwo_path.c_str());
+        continue;
+      }
+
       auto file = MmapInputFileFactory().OpenFile(dwo_path);
       dwarf::File dwo_dwarf;
       cu.dwarf().open(*file, &dwo_dwarf, sink);
diff --git a/tests/dwarf/debug_info/missing-dwo-file.test b/tests/dwarf/debug_info/missing-dwo-file.test
new file mode 100644
index 0000000..a2578e8
--- /dev/null
+++ b/tests/dwarf/debug_info/missing-dwo-file.test
@@ -0,0 +1,66 @@
+# Test that missing .dwo files produce a warning but don't fail analysis.
+
+# RUN: %yaml2obj %s -o %t.obj
+# RUN: %bloaty %t.obj -d compileunits 2>&1 | %FileCheck %s
+
+# CHECK: Warning: DWO file not found: /nonexistent/path/missing.dwo
+
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_DYN
+  Machine:         EM_X86_64
+ProgramHeaders:
+  - Type:            PT_LOAD
+    Flags:           [ PF_X, PF_R ]
+    FirstSec:        .text
+    LastSec:         .text
+    VAddr:           0x1000
+    Align:           0x1000
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x10
+    Size:            0x50
+  - Name:            .debug_addr
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x1
+    Content:         '0010000000000000'
+DWARF:
+  debug_str:
+    - /nonexistent/path/missing.dwo
+    - /some/comp/dir
+  debug_abbrev:
+    - ID:              0
+      Table:
+        - Code:            0x1
+          Tag:             DW_TAG_compile_unit
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_comp_dir
+              Form:            DW_FORM_strp
+            - Attribute:       DW_AT_GNU_dwo_name
+              Form:            DW_FORM_strp
+            - Attribute:       DW_AT_GNU_dwo_id
+              Form:            DW_FORM_data8
+            - Attribute:       DW_AT_GNU_addr_base
+              Form:            DW_FORM_sec_offset
+  debug_info:
+    - Version:         4
+      AbbrevTableID:   0
+      AbbrOffset:      0x0
+      AddrSize:        8
+      Entries:
+        - AbbrCode:        0x1
+          Values:
+            # comp_dir offset (points to "/some/comp/dir")
+            - Value:           0x22
+            # dwo_name offset (points to "/nonexistent/path/missing.dwo")
+            - Value:           0x0
+            # dwo_id
+            - Value:           0x1234567890abcdef
+            # addr_base
+            - Value:           0x0