Remove 'z' in .zdebug when decompressing a section.

When decompressing a compressed debug section, we drop SHF_COMPRESSED
flag but we didn't drop "z" in ".zdebug" section name. This patch does
that for consistency.

This change also fixes the issue that .zdebug_gnu_pubnames are not
dropped when we are creating a .gdb_index section.

llvm-svn: 324949

lld/ELF/InputSection.cpp

@@ -181,17 +181,26 @@ void InputSectionBase::maybeDecompress() {
   if (DecompressBuf || !Decompressor::isCompressedELFSection(Flags, Name))
     return;
 
+  // Decompress a section.
   Decompressor Dec = check(Decompressor::create(Name, toStringRef(Data),
                                                 Config->IsLE, Config->Is64));
 
   size_t Size = Dec.getDecompressedSize();
-  DecompressBuf.reset(new char[Size]());
+  DecompressBuf.reset(new char[Size + Name.size()]());
   if (Error E = Dec.decompress({DecompressBuf.get(), Size}))
     fatal(toString(this) +
           ": decompress failed: " + llvm::toString(std::move(E)));
 
   Data = makeArrayRef((uint8_t *)DecompressBuf.get(), Size);
   Flags &= ~(uint64_t)SHF_COMPRESSED;
+
+  // A section name may have been altered if compressed. If that's
+  // the case, restore the original name. (i.e. ".zdebug_" -> ".debug_")
+  if (Name.startswith(".zdebug")) {
+    DecompressBuf[Size] = '.';
+    memcpy(&DecompressBuf[Size + 1], Name.data() + 2, Name.size() - 2);
+    Name = StringRef(&DecompressBuf[Size], Name.size() - 1);
+  }
 }
 
 InputSection *InputSectionBase::getLinkOrderDep() const {

lld/ELF/Writer.cpp

@@ -88,11 +88,6 @@ private:
 } // anonymous namespace
 
 StringRef elf::getOutputSectionName(InputSectionBase *S) {
-  // ".zdebug_" is a prefix for ZLIB-compressed sections.
-  // Because we decompressed input sections, we want to remove 'z'.
-  if (S->Name.startswith(".zdebug_"))
-    return Saver.save("." + S->Name.substr(2));
-
   if (Config->Relocatable)
     return S->Name;
 

lld/test/ELF/Inputs/gdb-index.s

@@ -1,8 +1,8 @@
 .text
 .Ltext0:
-.globl main2
+.globl aaaaaaaaaaaaaaaa
-.type main2, @function
+.type aaaaaaaaaaaaaaaa, @function
-main2:
+aaaaaaaaaaaaaaaa:
  nop
  nop
 .Letext0:
@@ -59,7 +59,7 @@ main2:
 .long 0x33
 .long 0x18
 .byte 0x30
-.string "main2"
+.string "aaaaaaaaaaaaaaaa"
 .long 0
 
 .section .debug_gnu_pubtypes,"",@progbits

lld/test/ELF/gdb-index.s

@@ -2,8 +2,18 @@
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t1.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/gdb-index.s -o %t2.o
 # RUN: ld.lld --gdb-index %t1.o %t2.o -o %t
-# RUN: llvm-dwarfdump -gdb-index %t | FileCheck %s
+
 # RUN: llvm-objdump -d %t | FileCheck %s --check-prefix=DISASM
+# RUN: llvm-dwarfdump -gdb-index %t | FileCheck %s --check-prefix=DWARF
+# RUN: llvm-readelf -sections %t | FileCheck %s --check-prefix=SECTION
+
+# RUN: llvm-mc -compress-debug-sections=zlib-gnu -filetype=obj -triple=x86_64-pc-linux \
+# RUN:   %p/Inputs/gdb-index.s -o %t2.o
+# RUN: ld.lld --gdb-index %t1.o %t2.o -o %t
+
+# RUN: llvm-objdump -d %t | FileCheck %s --check-prefix=DISASM
+# RUN: llvm-dwarfdump -gdb-index %t | FileCheck %s --check-prefix=DWARF
+# RUN: llvm-readelf -sections %t | FileCheck %s --check-prefix=SECTION
 
 # DISASM:       Disassembly of section .text:
 # DISASM:       entrypoint:
@@ -11,29 +21,31 @@
 # DISASM-CHECK:   201001: cc int3
 # DISASM-CHECK:   201002: cc int3
 # DISASM-CHECK:   201003: cc int3
-# DISASM:       main2:
+# DISASM:       aaaaaaaaaaaaaaaa:
 # DISASM-CHECK:   201004: 90 nop
 # DISASM-CHECK:   201005: 90 nop
 
-# CHECK:      .gnu_index contents:
+# DWARF:      .gnu_index contents:
-# CHECK-NEXT:    Version = 7
+# DWARF-NEXT:    Version = 7
-# CHECK:       CU list offset = 0x18, has 2 entries:
+# DWARF:       CU list offset = 0x18, has 2 entries:
-# CHECK-NEXT:    0: Offset = 0x0, Length = 0x34
+# DWARF-NEXT:    0: Offset = 0x0, Length = 0x34
-# CHECK-NEXT:    1: Offset = 0x34, Length = 0x34
+# DWARF-NEXT:    1: Offset = 0x34, Length = 0x34
-# CHECK:       Address area offset = 0x38, has 2 entries:
+# DWARF:       Address area offset = 0x38, has 2 entries:
-# CHECK-NEXT:    Low/High address = [0x201000, 0x201001) (Size: 0x1), CU id = 0
+# DWARF-NEXT:    Low/High address = [0x201000, 0x201001) (Size: 0x1), CU id = 0
-# CHECK-NEXT:    Low/High address = [0x201004, 0x201006) (Size: 0x2), CU id = 1
+# DWARF-NEXT:    Low/High address = [0x201004, 0x201006) (Size: 0x2), CU id = 1
-# CHECK:       Symbol table offset = 0x60, size = 1024, filled slots:
+# DWARF:       Symbol table offset = 0x60, size = 1024, filled slots:
-# CHECK-NEXT:    754: Name offset = 0x27, CU vector offset = 0x8
+# DWARF-NEXT:    512: Name offset = 0x2b, CU vector offset = 0x14
-# CHECK-NEXT:	   String name: int, CU vector index: 1
+# DWARF-NEXT:      String name: aaaaaaaaaaaaaaaa, CU vector index: 2
-# CHECK-NEXT:    822: Name offset = 0x1c, CU vector offset = 0x0
+# DWARF-NEXT:    754: Name offset = 0x27, CU vector offset = 0x8
-# CHECK-NEXT:	   String name: entrypoint, CU vector index: 0
+# DWARF-NEXT:      String name: int, CU vector index: 1
-# CHECK-NEXT:    956: Name offset = 0x2b, CU vector offset = 0x14
+# DWARF-NEXT:    822: Name offset = 0x1c, CU vector offset = 0x0
-# CHECK-NEXT:      String name: main2, CU vector index: 2
+# DWARF-NEXT:      String name: entrypoint, CU vector index: 0
-# CHECK:       Constant pool offset = 0x2060, has 3 CU vectors:
+# DWARF:       Constant pool offset = 0x2060, has 3 CU vectors:
-# CHECK-NEXT:    0(0x0): 0x30000000
+# DWARF-NEXT:    0(0x0): 0x30000000
-# CHECK-NEXT:    1(0x8): 0x90000000 0x90000001
+# DWARF-NEXT:    1(0x8): 0x90000000 0x90000001
-# CHECK-NEXT:    2(0x14): 0x30000001
+# DWARF-NEXT:    2(0x14): 0x30000001
+
+# SECTION-NOT: debug_gnu_pubnames
 
 # RUN: ld.lld --gdb-index --no-gdb-index %t1.o %t2.o -o %t2
 # RUN: llvm-readobj -sections %t2 | FileCheck -check-prefix=NOGDB %s