ELF: --gdb-index: Do not add dead sections to the address area.

[pcc]

Summary

Fixes PR33032.

[grimar]

LGTM with a nit.

lld/test/ELF/Inputs/gdb-index-gc-sections.o.sh

4 ↗

(On Diff #98936)

Please add comment about which clang version was used.
Also do you really need -fdebug-compilation-dir ?

[pcc]

lld/test/ELF/Inputs/gdb-index-gc-sections.o.sh

4 ↗

(On Diff #98936)

Please add comment about which clang version was used.

Will do while moving to .s.

Also do you really need -fdebug-compilation-dir ?

Yes otherwise my cwd leaks into the object file.

lld/trunk/ELF/SyntheticSections.cpp

readCuList(DWARFContext &Dwarf, InputSection *Sec) {
   for (std::unique_ptr<DWARFCompileUnit> &CU : Dwarf.compile_units())
     Ret.push_back({Sec->OutSecOff + CU->getOffset(), CU->getLength() + 4});
   return Ret;
 }
 
 static InputSectionBase *findSection(ArrayRef<InputSectionBase *> Arr,
                                      uint64_t Offset) {
   for (InputSectionBase *S : Arr)
-    if (S && S != &InputSection::Discarded)
+    if (S && S != &InputSection::Discarded && S->Live)
       if (Offset >= S->getOffsetInFile() &&
           Offset < S->getOffsetInFile() + S->getSize())
         return S;
   return nullptr;
 }
 
 static std::vector<AddressEntry>
 readAddressArea(DWARFContext &Dwarf, InputSection *Sec, size_t CurrentCU) {

lld/trunk/test/ELF/gdb-index-gc-sections.s

+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux -o %t %s
+# RUN: ld.lld --gdb-index --gc-sections -o %t2 %t
+# RUN: llvm-dwarfdump -debug-dump=gdb_index %t2 | FileCheck %s
+
+# CHECK: Address area offset = 0x28, has 1 entries:
+# CHECK-NEXT:    Low/High address = [0x201000, 0x201001) (Size: 0x1), CU id = 0
+
+# Generated with: (clang r302976)
+# echo "void _start() {} void dead() {}" | \
+# clang -Os -g -S -ffunction-sections -o gdb-index-gc-sections.s -x c - -Xclang -fdebug-compilation-dir -Xclang .
+
+  .text
+  .file "-"
+  .section  .text._start,"ax",@progbits
+  .globl  _start
+  .type _start,@function
+_start:                                 # @_start
+.Lfunc_begin0:
+  .file 1 "<stdin>"
+  .loc  1 1 0                   # <stdin>:1:0
+  .cfi_startproc
+# BB#0:                                 # %entry
+  .loc  1 1 16 prologue_end     # <stdin>:1:16
+  retq
+.Ltmp0:
+.Lfunc_end0:
+  .size _start, .Lfunc_end0-_start
+  .cfi_endproc
+
+  .section  .text.dead,"ax",@progbits
+  .globl  dead
+  .type dead,@function
+dead:                                   # @dead
+.Lfunc_begin1:
+  .loc  1 1 0                   # <stdin>:1:0
+  .cfi_startproc
+# BB#0:                                 # %entry
+  .loc  1 1 31 prologue_end     # <stdin>:1:31
+  retq
+.Ltmp1:
+.Lfunc_end1:
+  .size dead, .Lfunc_end1-dead
+  .cfi_endproc
+
+  .section  .debug_str,"MS",@progbits,1
+.Linfo_string0:
+  .asciz  "clang version 5.0.0 "  # string offset=0
+.Linfo_string1:
+  .asciz  "-"                     # string offset=21
+.Linfo_string2:
+  .asciz  "."                     # string offset=23
+.Linfo_string3:
+  .asciz  "_start"                # string offset=25
+.Linfo_string4:
+  .asciz  "dead"                  # string offset=32
+  .section  .debug_loc,"",@progbits
+  .section  .debug_abbrev,"",@progbits
+  .byte 1                       # Abbreviation Code
+  .byte 17                      # DW_TAG_compile_unit
+  .byte 1                       # DW_CHILDREN_yes
+  .byte 37                      # DW_AT_producer
+  .byte 14                      # DW_FORM_strp
+  .byte 19                      # DW_AT_language
+  .byte 5                       # DW_FORM_data2
+  .byte 3                       # DW_AT_name
+  .byte 14                      # DW_FORM_strp
+  .byte 16                      # DW_AT_stmt_list
+  .byte 23                      # DW_FORM_sec_offset
+  .byte 27                      # DW_AT_comp_dir
+  .byte 14                      # DW_FORM_strp
+  .byte 17                      # DW_AT_low_pc
+  .byte 1                       # DW_FORM_addr
+  .byte 85                      # DW_AT_ranges
+  .byte 23                      # DW_FORM_sec_offset
+  .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 18                      # DW_AT_high_pc
+  .byte 6                       # DW_FORM_data4
+  .byte 64                      # DW_AT_frame_base
+  .byte 24                      # DW_FORM_exprloc
+  .byte 3                       # DW_AT_name
+  .byte 14                      # DW_FORM_strp
+  .byte 58                      # DW_AT_decl_file
+  .byte 11                      # DW_FORM_data1
+  .byte 59                      # DW_AT_decl_line
+  .byte 11                      # DW_FORM_data1
+  .byte 63                      # DW_AT_external
+  .byte 25                      # DW_FORM_flag_present
+  .byte 0                       # EOM(1)
+  .byte 0                       # EOM(2)
+  .byte 0                       # EOM(3)
+  .section  .debug_info,"",@progbits
+.Lcu_begin0:
+  .long 81                      # Length of Unit
+  .short  4                       # DWARF version number
+  .long .debug_abbrev           # Offset Into Abbrev. Section
+  .byte 8                       # Address Size (in bytes)
+  .byte 1                       # Abbrev [1] 0xb:0x4a DW_TAG_compile_unit
+  .long .Linfo_string0          # DW_AT_producer
+  .short  12                      # DW_AT_language
+  .long .Linfo_string1          # DW_AT_name
+  .long .Lline_table_start0     # DW_AT_stmt_list
+  .long .Linfo_string2          # DW_AT_comp_dir
+  .quad 0                       # DW_AT_low_pc
+  .long .Ldebug_ranges0         # DW_AT_ranges
+  .byte 2                       # Abbrev [2] 0x2a:0x15 DW_TAG_subprogram
+  .quad .Lfunc_begin0           # DW_AT_low_pc
+  .long .Lfunc_end0-.Lfunc_begin0 # DW_AT_high_pc
+  .byte 1                       # DW_AT_frame_base
+  .byte 87
+  .long .Linfo_string3          # DW_AT_name
+  .byte 1                       # DW_AT_decl_file
+  .byte 1                       # DW_AT_decl_line
+                                        # DW_AT_external
+  .byte 2                       # Abbrev [2] 0x3f:0x15 DW_TAG_subprogram
+  .quad .Lfunc_begin1           # DW_AT_low_pc
+  .long .Lfunc_end1-.Lfunc_begin1 # DW_AT_high_pc
+  .byte 1                       # DW_AT_frame_base
+  .byte 87
+  .long .Linfo_string4          # DW_AT_name
+  .byte 1                       # DW_AT_decl_file
+  .byte 1                       # DW_AT_decl_line
+                                        # DW_AT_external
+  .byte 0                       # End Of Children Mark
+  .section  .debug_ranges,"",@progbits
+.Ldebug_ranges0:
+  .quad .Lfunc_begin0
+  .quad .Lfunc_end0
+  .quad .Lfunc_begin1
+  .quad .Lfunc_end1
+  .quad 0
+  .quad 0
+  .section  .debug_macinfo,"",@progbits
+.Lcu_macro_begin0:
+  .byte 0                       # End Of Macro List Mark
+  .section  .debug_pubnames,"",@progbits
+  .long .LpubNames_end0-.LpubNames_begin0 # Length of Public Names Info
+.LpubNames_begin0:
+  .short  2                       # DWARF Version
+  .long .Lcu_begin0             # Offset of Compilation Unit Info
+  .long 85                      # Compilation Unit Length
+  .long 42                      # DIE offset
+  .asciz  "_start"                # External Name
+  .long 63                      # DIE offset
+  .asciz  "dead"                  # External Name
+  .long 0                       # End Mark
+.LpubNames_end0:
+
+  .ident  "clang version 5.0.0 "
+  .section  ".note.GNU-stack","",@progbits
+  .section  .debug_line,"",@progbits
+.Lline_table_start0: