Index: ELF/InputFiles.cpp
===================================================================
--- ELF/InputFiles.cpp
+++ ELF/InputFiles.cpp
@@ -121,11 +121,22 @@
   DWARFDataExtractor LineData(Obj, Obj.getLineSection(), Config->IsLE,
                               Config->Wordsize);
 
-  // The second parameter is offset in .debug_line section
-  // for compilation unit (CU) of interest. We have only one
-  // CU (object file), so offset is always 0.
-  const DWARFDebugLine::LineTable *LT =
-      DwarfLine->getOrParseLineTable(LineData, 0, Dwarf, nullptr);
+  const DWARFDebugLine::LineTable *LT = nullptr;
+  // The second parameter in getOrParseLineTable is the offset in the
+  // .debug_line section for the compilation unit (CU) of interest. We assume we
+  // have only one CU (object file), so the offset is always 0.
+  // FIXME: Under some circustances, we can have more than one CU, e.g. objects
+  // built via -r links or LTO. See PR36793.
+  if (LineData.isValidOffset(0)) {
+    Expected<const DWARFDebugLine::LineTable *> ErrOrLineTable =
+        DwarfLine->getOrParseLineTable(LineData, 0, Dwarf, nullptr, warn);
+    if (ErrOrLineTable)
+      LT = *ErrOrLineTable;
+    else
+      handleAllErrors(ErrOrLineTable.takeError(),
+                      [&](DebugLineError &Err) { warn(Err.message()); },
+                      [&](ErrorInfoBase &Err) { error(Err.message()); });
+  }
   if (!LT)
     return;
 
Index: test/ELF/Inputs/undef-bad-debug.s
===================================================================
--- test/ELF/Inputs/undef-bad-debug.s
+++ test/ELF/Inputs/undef-bad-debug.s
@@ -1,7 +1,37 @@
 .section .text,"ax"
 sym:
     .quad zed6
-    
+
+.section .debug_line,"",@progbits
+    .long .Lunit_end - .Lunit_start # unit length
+.Lunit_start:
+    .short 4                        # version
+    .long .Lprologue_end - .Lprologue_start # prologue length
+.Lprologue_start:
+    .byte 1                         # minimum instruction length
+    .byte 1                         # maximum operatiosn per instruction
+    .byte 1                         # default is_stmt
+    .byte -5                        # line base
+    .byte 14                        # line range
+    .byte 13                        # opcode base
+    .byte 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1 # standard opcode lengths
+    .asciz "dir"                    # include directories
+    .byte 0
+    .asciz "undef-bad-debug.s"      # file names
+    .byte 1, 0, 0
+    .byte 0
+    .byte 0                         # extraneous byte
+.Lprologue_end:
+    .byte 0, 9, 2                   # DW_LNE_set_address
+    .quad sym
+    .byte 3                         # DW_LNS_advance_line
+    .byte 10
+    .byte 1                         # DW_LNS_copy
+    .byte 2                         # DW_LNS_advance_pc
+    .byte 8
+    .byte 0, 1, 1                   # DW_LNE_end_sequence
+.Lunit_end:
+
 .section .debug_info,"",@progbits
     .long   .Lcu_end - .Lcu_start   # Length of Unit
 .Lcu_start:
Index: test/ELF/no-line-parser-errors-if-empty-section.s
===================================================================
--- test/ELF/no-line-parser-errors-if-empty-section.s
+++ test/ELF/no-line-parser-errors-if-empty-section.s
@@ -0,0 +1,21 @@
+# REQUIRES: x86
+
+# LLD uses the debug data to get information for error messages, if possible.
+# However, if the debug line section is empty, we should not attempt to parse
+# it, as that would result in errors from the parser.
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: not ld.lld %t.o -o %t.elf 2>&1 | FileCheck %s
+
+# CHECK-NOT: warning:
+# CHECK-NOT: error:
+# CHECK: error: undefined symbol: undefined
+# CHECK-NEXT: {{.*}}.o:(.text+0x1)
+# CHECK-NOT: warning:
+# CHECK-NOT: error:
+
+.globl _start
+_start:
+    callq undefined
+
+.section .debug_line,"",@progbits
Index: test/ELF/no-line-parser-errors-if-no-section.s
===================================================================
--- test/ELF/no-line-parser-errors-if-no-section.s
+++ test/ELF/no-line-parser-errors-if-no-section.s
@@ -0,0 +1,19 @@
+# REQUIRES: x86
+
+# LLD uses the debug data to get information for error messages, if possible.
+# However, if there is no debug line section, we should not attempt to parse
+# it, as that would result in errors from the parser.
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: not ld.lld %t.o -o %t.elf 2>&1 | FileCheck %s
+
+# CHECK-NOT: warning:
+# CHECK-NOT: error:
+# CHECK: error: undefined symbol: undefined
+# CHECK-NEXT: {{.*}}.o:(.text+0x1)
+# CHECK-NOT: warning:
+# CHECK-NOT: error:
+
+.globl _start
+_start:
+    callq undefined
Index: test/ELF/undef.s
===================================================================
--- test/ELF/undef.s
+++ test/ELF/undef.s
@@ -34,6 +34,7 @@
 # CHECK: >>> referenced by undef-debug.s:11 (dir{{/|\\}}undef-debug.s:11)
 # CHECK: >>>               {{.*}}.o:(.text.2+0x0)
 
+# CHECK: warning: parsing line table prologue at 0x00000000 should have ended at 0x00000038 but it ended at 0x00000037
 # CHECK: error: undefined symbol: zed6
 # CHECK: >>> referenced by {{.*}}tmp4.o:(.text+0x0)