[DWARFYAML][debug_abbrev] Emit 0 byte for terminating abbreviations.

[Higuoxing]

Summary

The abbreviations for a given compilation unit end with an entry
consisting of a 0 byte for the abbreviation code.

[jhenderson]

LGTM, with on suggestion.

llvm/test/tools/yaml2obj/ELF/DWARF/debug-abbrev.yaml

46–47

How about "attr terminator" and "abbrev terminator".

[Higuoxing]

Address comment.

llvm/lib/ObjectYAML/DWARFEmitter.cpp

for (auto Attr : AbbrevDecl.Attributes) {
       encodeULEB128(Attr.Form, OS);
       if (Attr.Form == dwarf::DW_FORM_implicit_const)
         encodeSLEB128(Attr.Value, OS);
     }
     encodeULEB128(0, OS);
     encodeULEB128(0, OS);
   }
 
+  // The abbreviations for a given compilation unit end with an entry consisting
+  // of a 0 byte for the abbreviation code.
+  OS.write_zeros(1);
+
   return Error::success();
 }
 
 Error DWARFYAML::emitDebugAranges(raw_ostream &OS, const DWARFYAML::Data &DI) {
   for (auto Range : DI.ARanges) {
     auto HeaderStart = OS.tell();
     writeInitialLength(Range.Format, Range.Length, OS, DI.IsLittleEndian);
     writeInteger((uint16_t)Range.Version, OS, DI.IsLittleEndian);

llvm/test/ObjectYAML/MachO/DWARF2-AddrSize8-FormValues.yaml

Sections:
         nreloc:          0
         flags:           0x00000000
         reserved1:       0x00000000
         reserved2:       0x00000000
         reserved3:       0x00000000
       - sectname:        __debug_abbrev
         segname:         __DWARF
         addr:            0x000000010000312C
-        size:            84
+        size:            86
         offset:          0x00002167
         align:           0
         reloff:          0x00000000
         nreloc:          0
         flags:           0x00000000
         reserved1:       0x00000000
         reserved2:       0x00000000
         reserved3:       0x00000000
       - sectname:        __debug_str
         segname:         __DWARF
         addr:            0x0000000100003178
         size:            83
-        offset:          0x000021BB
+        offset:          0x000021BC
         align:           0
         reloff:          0x00000000
         nreloc:          0
         flags:           0x00000000
         reserved1:       0x00000000
         reserved2:       0x00000000
         reserved3:       0x00000000
       - sectname:        __apple_names

llvm/test/tools/yaml2obj/ELF/DWARF/debug-abbrev.yaml

 ## Test that yaml2obj emits .debug_abbrev section.
 
 ## a) Generate the .debug_abbrev section from the "DWARF" entry.
 
 # RUN: yaml2obj --docnum=1 %s -o %t1.o
 # RUN: llvm-readobj --sections --section-data %t1.o | \
-# RUN:   FileCheck -DSIZE=38 -DADDRALIGN=1 %s --check-prefixes=SHDR,CONTENT
+# RUN:   FileCheck -DSIZE=39 -DADDRALIGN=1 %s --check-prefixes=SHDR,CONTENT
 
 #         SHDR: Index: 1
 #    SHDR-NEXT: Name: .debug_abbrev (1)
 #    SHDR-NEXT: Type: SHT_PROGBITS (0x1)
 #    SHDR-NEXT: Flags [ (0x0)
 #    SHDR-NEXT: ]
 #    SHDR-NEXT: Address: 0x0
 #    SHDR-NEXT: Offset: 0x40

 ##                          ^--- terminating entry                      ^-   DW_CHILDREN_no    1-byte
 ##                                                                        ^- DW_AT_call_pc     ULEB128 (0x81)
 ##
 #      CONTENT:         01810104                                    02A04021 |..............@!|
 ##                      --                                          ^-       Form: reserved         ULEB128
 ##                        ^---   Form: invalid       ULEB128 (0x81)   ^---   Attribute: reserved    ULEB128 (0x2020)
 ##                            ^- Attribute: reserved ULEB128              ^- DW_FORM_implicit_const ULEB128
 ##
-# CONTENT-NEXT:   0020: CEC2F105                                    0000     |......|
-##                      ^------- Value SLEB128 (12345678)           ^---     terminating entry
+# CONTENT-NEXT:   0020: CEC2F105                                    000000   |.......|
+##                      ^------- Value SLEB128 (12345678)           ^---     terminating entry for attributes.
+##                                                                      ^-   terminating entry for abbreviations.
 # CONTENT-NEXT: )
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_EXEC
   Machine: EM_X86_64

 
 ## f) Test that all the properties can be overridden by the section header when
 ## the "debug_abbrev" entry doesn't exist.
 
 # RUN: yaml2obj --docnum=6 %s -o %t6.o
 # RUN: llvm-readelf --sections %t6.o | FileCheck %s --check-prefix=OVERRIDDEN
 
 #      OVERRIDDEN: [Nr] Name          Type   Address          Off    Size   ES Flg Lk Inf Al
-#      OVERRIDDEN: [ 1] .debug_abbrev STRTAB 0000000000002020 000050 000005 01   A  2   1  2
-# OVERRIDDEN-NEXT: [ 2] .sec          STRTAB 0000000000000000 000055 000000 00      0   0  0
+#      OVERRIDDEN: [ 1] .debug_abbrev STRTAB 0000000000002020 000050 000006 01   A  2   1  2
+# OVERRIDDEN-NEXT: [ 2] .sec          STRTAB 0000000000000000 000056 000000 00      0   0  0
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_EXEC
   Machine: EM_X86_64
 Sections:
   - Name:         .debug_abbrev
     Type:         SHT_STRTAB  ## SHT_PROGBITS by default.
     Flags:        [SHF_ALLOC] ## 0 by default.
     Link:         .sec        ## 0 by default.
     EntSize:      1           ## 0 by default.
     Info:         1           ## 0 by default.
     AddressAlign: 2           ## 0 by default.
     Address:      0x2020      ## 0x00 by default.
     Offset:       0x50        ## 0x40 for the first section.
-    Size:         0x05        ## Set the "Size" so that we can reuse the check tag "OVERRIDDEN".
+    Size:         0x06        ## Set the "Size" so that we can reuse the check tag "OVERRIDDEN".
   - Name:         .sec        ## Linked by .debug_abbrev.
     Type:         SHT_STRTAB
 
 ## g) Test that all the properties can be overridden by the section header when
 ## the "debug_abbrev" entry exists.
 
 # RUN: yaml2obj --docnum=7 %s -o %t7.o
 # RUN: llvm-readelf --sections %t7.o | FileCheck %s --check-prefix=OVERRIDDEN

llvm/test/tools/yaml2obj/ELF/DWARF/debug-info.yaml

 ## Test that yaml2obj emits .debug_info section.
 
 ## a) Generate the .debug_info section from the "DWARF" entry.
 
 ## Generate and verify a DWARF32 little endian .debug_info (DWARFv5) section.
 
 # RUN: yaml2obj --docnum=1 -DENDIAN=ELFDATA2LSB %s -o %t1.le.o
 # RUN: llvm-readobj --sections --section-data %t1.le.o | \
-# RUN:   FileCheck -DINDEX=2 -DNAME=15 -DOFFSET=0x9A -DSIZE=171 -DADDRALIGN=1 %s --check-prefixes=SHDR,DWARF32-LE-CONTENT
+# RUN:   FileCheck -DINDEX=2 -DNAME=15 -DOFFSET=0x9B -DSIZE=171 -DADDRALIGN=1 %s --check-prefixes=SHDR,DWARF32-LE-CONTENT
 
 #                    SHDR: Index: [[INDEX]]
 #               SHDR-NEXT: Name: .debug_info ([[NAME]])
 #               SHDR-NEXT: Type: SHT_PROGBITS (0x1)
 #               SHDR-NEXT: Flags [ (0x0)
 #               SHDR-NEXT: ]
 #               SHDR-NEXT: Address: 0x0
 #               SHDR-NEXT: Offset: [[OFFSET]]
- Length:     0x5678
             - BlockData:        ## DW_FORM_block2
                 - 0x12
                 - 0x34
 
 ## Generate and verify a DWARF32 big endian .debug_info (DWARFv4) section.
 
 # RUN: yaml2obj --docnum=1 -DENDIAN=ELFDATA2MSB %s -o %t1.be.o
 # RUN: llvm-readobj --sections --section-data %t1.be.o | \
-# RUN:   FileCheck -DINDEX=2 -DNAME=15 -DOFFSET=0x9A -DSIZE=171 -DADDRALIGN=1 %s --check-prefixes=SHDR,DWARF32-BE-CONTENT
+# RUN:   FileCheck -DINDEX=2 -DNAME=15 -DOFFSET=0x9B -DSIZE=171 -DADDRALIGN=1 %s --check-prefixes=SHDR,DWARF32-BE-CONTENT
 
 # DWARF32-BE-CONTENT-NEXT: SectionData (
 # DWARF32-BE-CONTENT-NEXT:   0000: 00001234 00050204 00001234 01123456
 ##                                 ^-------                            unit_length (4-byte)
 ##                                          ^---                       version (2-byte)
 ##                                              ^-                     unit_type (1-byte) DW_UT_type
 ##                                                ^-                   address_size (1-byte)
 ##                                                   ^-------          debug_abbrev_offset (4-byte)