From d626bb872333b901ee6147522a48bfa2be994a7d Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas@devlieghere.com>
Date: Wed, 23 Sep 2020 22:00:57 -0700
Subject: [PATCH 1/2] [dwarfdump] Warn for tags with DW_CHILDREN_yes but no
 children.

Flag DIEs that have DW_CHILDREN_yes set in their abbreviation but don't
actually have any children.

rdar://59809554

Differential revision: https://reviews.llvm.org/D88048

(cherry picked from commit e1ef7183c6f008fa13cbe273500b020c4fad1252)
---
 llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp    |  9 ++++++++
 .../test/DebugInfo/X86/skeleton-unit-verify.s |  4 +++-
 .../tools/llvm-dwarfdump/X86/no-children.yaml | 23 +++++++++++++++++++
 .../llvm-dwarfdump/X86/verify_die_ranges.s    |  3 ++-
 4 files changed, 37 insertions(+), 2 deletions(-)
 create mode 100644 llvm/test/tools/llvm-dwarfdump/X86/no-children.yaml

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp b/llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp
index 3a83317a73a3b..895dd7d2a575d 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp
@@ -172,6 +172,15 @@ unsigned DWARFVerifier::verifyUnitContents(DWARFUnit &Unit) {
       NumUnitErrors += verifyDebugInfoForm(Die, AttrValue);
     }
 
+    if (Die.hasChildren()) {
+      if (Die.getFirstChild().isValid() &&
+          Die.getFirstChild().getTag() == DW_TAG_null) {
+        warn() << dwarf::TagString(Die.getTag())
+               << " has DW_CHILDREN_yes but DIE has no children: ";
+        Die.dump(OS);
+      }
+    }
+
     NumUnitErrors += verifyDebugInfoCallSite(Die);
   }
 
diff --git a/llvm/test/DebugInfo/X86/skeleton-unit-verify.s b/llvm/test/DebugInfo/X86/skeleton-unit-verify.s
index d990d918cef6f..95fbd113942a4 100644
--- a/llvm/test/DebugInfo/X86/skeleton-unit-verify.s
+++ b/llvm/test/DebugInfo/X86/skeleton-unit-verify.s
@@ -3,6 +3,8 @@
 
 # CHECK: Verifying .debug_abbrev...
 # CHECK-NEXT: Verifying .debug_info Unit Header Chain...
+# CHECK-NEXT: warning: DW_TAG_skeleton_unit has DW_CHILDREN_yes but DIE has no children
+# CHECK-NEXT: DW_TAG_skeleton_unit
 # CHECK-NEXT: error: Skeleton compilation unit has children.
 # CHECK-NEXT: Verifying .debug_info references...
 # CHECK-NEXT: Verifying .debug_types Unit Header Chain...
@@ -30,7 +32,7 @@
         .byte   8                       # Address Size (in bytes)
         .long   .debug_abbrev           # Offset Into Abbrev. Section
         .quad   -6573227469967412476
-        .byte   1                       # Abbrev [1] 
+        .byte   1                       # Abbrev [1]
         .byte   0
 .Lcu_end0:
         .long   .Lcu_end1-.Lcu_start1 # Length of Unit
diff --git a/llvm/test/tools/llvm-dwarfdump/X86/no-children.yaml b/llvm/test/tools/llvm-dwarfdump/X86/no-children.yaml
new file mode 100644
index 0000000000000..1417ab2bdc3f0
--- /dev/null
+++ b/llvm/test/tools/llvm-dwarfdump/X86/no-children.yaml
@@ -0,0 +1,23 @@
+# RUN: yaml2obj %s | llvm-dwarfdump -verify - | FileCheck %s
+# CHECK: warning: DW_TAG_compile_unit has DW_CHILDREN_yes but DIE has no children
+
+--- !ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data:  ELFDATA2LSB
+  Type:  ET_EXEC
+DWARF:
+  debug_abbrev:
+    - Table:
+        - Tag:      DW_TAG_compile_unit
+          Children: DW_CHILDREN_yes
+          Attributes:
+            - Attribute: DW_AT_low_pc
+              Form:      DW_FORM_data4
+  debug_info:
+    - Version: 4
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - Value: 0x1234
+        - AbbrCode: 0   ## Terminator for the current DIE.
diff --git a/llvm/test/tools/llvm-dwarfdump/X86/verify_die_ranges.s b/llvm/test/tools/llvm-dwarfdump/X86/verify_die_ranges.s
index ea357b728897e..ea461b27e3e7d 100644
--- a/llvm/test/tools/llvm-dwarfdump/X86/verify_die_ranges.s
+++ b/llvm/test/tools/llvm-dwarfdump/X86/verify_die_ranges.s
@@ -3,7 +3,8 @@
 # RUN: | FileCheck %s
 
 # CHECK: Verifying .debug_info Unit Header Chain...
-# CHECK-NEXT: error: Invalid address range [0x0000000000000007, 0x0000000000000006)
+# CHECK: warning: DW_TAG_compile_unit has DW_CHILDREN_yes but DIE has no children:
+# CHECK: error: Invalid address range [0x0000000000000007, 0x0000000000000006)
 
 	.section	__TEXT,__text,regular,pure_instructions
 	.macosx_version_min 10, 12

From c6c82ad21ddb2064e28b51b71402639a6aa6f90b Mon Sep 17 00:00:00 2001
From: Jonas Devlieghere <jonas@devlieghere.com>
Date: Tue, 6 Oct 2020 16:27:26 -0700
Subject: [PATCH 2/2] [llvm] Remove no-children.yaml test

This test relies on functionality in obj2yaml that's not present on the
stable branch. I made an attempt at backporting all the necessary
changes but quickly realized it was too much churn for this change.
---
 .../tools/llvm-dwarfdump/X86/no-children.yaml | 23 -------------------
 1 file changed, 23 deletions(-)
 delete mode 100644 llvm/test/tools/llvm-dwarfdump/X86/no-children.yaml

diff --git a/llvm/test/tools/llvm-dwarfdump/X86/no-children.yaml b/llvm/test/tools/llvm-dwarfdump/X86/no-children.yaml
deleted file mode 100644
index 1417ab2bdc3f0..0000000000000
--- a/llvm/test/tools/llvm-dwarfdump/X86/no-children.yaml
+++ /dev/null
@@ -1,23 +0,0 @@
-# RUN: yaml2obj %s | llvm-dwarfdump -verify - | FileCheck %s
-# CHECK: warning: DW_TAG_compile_unit has DW_CHILDREN_yes but DIE has no children
-
---- !ELF
-FileHeader:
-  Class: ELFCLASS64
-  Data:  ELFDATA2LSB
-  Type:  ET_EXEC
-DWARF:
-  debug_abbrev:
-    - Table:
-        - Tag:      DW_TAG_compile_unit
-          Children: DW_CHILDREN_yes
-          Attributes:
-            - Attribute: DW_AT_low_pc
-              Form:      DW_FORM_data4
-  debug_info:
-    - Version: 4
-      Entries:
-        - AbbrCode: 1
-          Values:
-            - Value: 0x1234
-        - AbbrCode: 0   ## Terminator for the current DIE.