[dsymutil] Do not crash on empty debug_range range.

The fix is trivial (The actual patch is 2 lines, but as it changes
indentation it looks like more).
clang does not produce this kind of (slightly bogus) debug info
anymore, thus I had to rely on a hand-crafted assembly test to trigger
that case.

llvm-svn: 246410

4 files changed, 69 insertions, 10 deletions

diff --git a/llvm/test/tools/dsymutil/Inputs/empty_range/1.o b/llvm/test/tools/dsymutil/Inputs/empty_range/1.o
new file mode 100644
index 00000000000..671bf4a0ccd
--- /dev/null
+++ b/llvm/test/tools/dsymutil/Inputs/empty_range/1.o
diff --git a/llvm/test/tools/dsymutil/X86/empty_range.s b/llvm/test/tools/dsymutil/X86/empty_range.s
new file mode 100644
index 00000000000..5c8ae6a1826
--- /dev/null
+++ b/llvm/test/tools/dsymutil/X86/empty_range.s
@@ -0,0 +1,57 @@
+# This test verifies that an empty range list in the .debug_ranges section
+# doesn't crash llvm-dsymutil. As clang does not produce this kind of debug
+# info anymore, we used this hand-crafted assembly file to produce a testcase
+# Compile with:
+#        llvm-mc -triple x86_64-apple-darwin -filetype=obj -o 1.o empty_range.o
+
+# RUN: llvm-dsymutil -f -y %p/dummy-debug-map.map -oso-prepend-path %p/../Inputs/empty_range -o - | llvm-dwarfdump -debug-dump=info - | FileCheck %s
+
+        .section	__TEXT,__text,regular,pure_instructions
+	.macosx_version_min 10, 11
+	.globl	__Z3foov
+	.align	4, 0x90
+__Z3foov:                               ## @_Z3foov
+Lfunc_begin0:
+	pushq	%rbp
+	movq	%rsp, %rbp
+	popq	%rbp
+	retq
+Lfunc_end0:
+	.section	__DWARF,__debug_abbrev,regular,debug
+Lsection_abbrev:
+	.byte	1                       ## Abbreviation Code
+	.byte	17                      ## DW_TAG_compile_unit
+	.byte	1                       ## DW_CHILDREN_yes
+	.byte	0                       ## EOM(1)
+	.byte	0                       ## EOM(2)
+	.byte	2                       ## Abbreviation Code
+	.byte	46                      ## DW_TAG_subprogram
+	.byte	0                       ## DW_CHILDREN_no
+	.byte	17                      ## DW_AT_low_pc
+	.byte	1                       ## DW_FORM_addr
+        .byte   0x55                    ## DW_AT_ranges
+        .byte   6                       ## DW_FORM_data4
+	.byte	0                       ## EOM(1)
+	.byte	0                       ## EOM(2)
+	.byte	0                       ## EOM(3)
+	.section	__DWARF,__debug_info,regular,debug
+Lsection_info:
+	.long	22                      ## Length of Unit
+	.short	2                       ## DWARF version number
+	.long	0                       ## Offset Into Abbrev. Section
+	.byte	8                       ## Address Size (in bytes)
+	.byte	1                       ## Abbrev [1]  DW_TAG_compile_unit
+	.byte	2                       ## Abbrev [2] DW_TAG_subprogram
+	.quad	Lfunc_begin0            ## DW_AT_low_pc
+        .long   0                       ## DW_AT_ranges (pointing at an empty entry)
+	.byte	0                       ## End Of Children Mark
+	.section	__DWARF,__debug_ranges,regular,debug
+Ldebug_range:
+        .long 0
+        .long 0
+
+# CHECK:  DW_TAG_compile_unit
+# CHECK:    DW_TAG_subprogram
+# CHECK-NEXT:      DW_AT_low_pc{{.*}}(0x0000000000010000)
+# CHECK-NEXT:      DW_AT_ranges{{.*}}(0x00000000)
+
diff --git a/llvm/test/tools/dsymutil/X86/lit.local.cfg b/llvm/test/tools/dsymutil/X86/lit.local.cfg
index 7b8ecfecc2b..ed9eba0b0d9 100644
--- a/llvm/test/tools/dsymutil/X86/lit.local.cfg
+++ b/llvm/test/tools/dsymutil/X86/lit.local.cfg
@@ -1,4 +1,4 @@
 if not 'X86' in config.root.targets:
     config.unsupported = True
 
-config.suffixes = ['.test', '.cpp']
+config.suffixes = ['.test', '.cpp', '.s']
diff --git a/llvm/tools/dsymutil/DwarfLinker.cpp b/llvm/tools/dsymutil/DwarfLinker.cpp
index 6881eab9c35..f3e48f5033e 100644
--- a/llvm/tools/dsymutil/DwarfLinker.cpp
+++ b/llvm/tools/dsymutil/DwarfLinker.cpp
@@ -688,7 +688,7 @@ void DwarfStreamer::emitRangesEntries(
   MS->SwitchSection(MC->getObjectFileInfo()->getDwarfRangesSection());
 
   // Offset each range by the right amount.
-  int64_t PcOffset = FuncRange.value() + UnitPcOffset;
+  int64_t PcOffset = Entries.empty() ? 0 : FuncRange.value() + UnitPcOffset;
   for (const auto &Range : Entries) {
     if (Range.isBaseAddressSelectionEntry(AddressSize)) {
       warn("unsupported base address selection operation",
@@ -2638,16 +2638,18 @@ void DwarfLinker::patchRangesForUnit(const CompileUnit &Unit,
     RangeAttribute.set(Streamer->getRangesSectionSize());
     RangeList.extract(RangeExtractor, &Offset);
     const auto &Entries = RangeList.getEntries();
-    const DWARFDebugRangeList::RangeListEntry &First = Entries.front();
+    if (!Entries.empty()) {
+      const DWARFDebugRangeList::RangeListEntry &First = Entries.front();
 
-    if (CurrRange == InvalidRange ||
-        First.StartAddress + OrigLowPc < CurrRange.start() ||
-        First.StartAddress + OrigLowPc >= CurrRange.stop()) {
-      CurrRange = FunctionRanges.find(First.StartAddress + OrigLowPc);
       if (CurrRange == InvalidRange ||
-          CurrRange.start() > First.StartAddress + OrigLowPc) {
-        reportWarning("no mapping for range.");
-        continue;
+          First.StartAddress + OrigLowPc < CurrRange.start() ||
+          First.StartAddress + OrigLowPc >= CurrRange.stop()) {
+        CurrRange = FunctionRanges.find(First.StartAddress + OrigLowPc);
+        if (CurrRange == InvalidRange ||
+            CurrRange.start() > First.StartAddress + OrigLowPc) {
+          reportWarning("no mapping for range.");
+          continue;
+        }
       }
     }