[LLD] add test for line number info related to differrent .text sections

[avl]

Summary

There is a bug for llvm-objdump which incorrectly reported line number info for object file if several .text sections presented. https://bugs.llvm.org/show_bug.cgi?id=40703 . This patch adds test for the same situation for LLD.

[grimar]

It is not clear from the description, so for other reviewers:

This test now passes without any LLD code changes.

This is relative to D58194, which changes the DWARF parsers interface slightly and
also makes a change on LLD side to conform to that interface.

LLD currently contains kind of hack (we have a TODO saying we want to remove it):
we update the relocation values by a getOffsetInFile for the purpose of error reporting:
https://github.com/llvm-mirror/lld/blob/master/ELF/DWARF.cpp#L88
https://github.com/llvm-mirror/lld/blob/master/ELF/InputFiles.cpp#L213

D58194 perhaps might allow us to revisit these places and remove the "TODO",
but I think it is nice to have a test case in LLD for the situation fixed in D58194 in any case.

lld/test/ELF/debug-line-obj.s

9

I am not sure it is clear enough to say that .debug_line contains overlapping addresses, it contains
unrelocated addresses, which are technically offsets and "overlaps" only because were not yet relocated.

I would suggest the following rewording:

When compiling with -ffunction-sections, .debug_line may contain descriptions of locations from the different text sections. Until relocated such descriptions might contain overlapping offsets. Check LLD is able to report the error locations correctly in this case.

252

It's a good practice to reduce the sample if possible.
It is hard to do for DWARF asm usually, but some of the parts
were obviously unused in the test, so I removed them, please use:

.text
.file  "test.cpp"
.section  .text._Z3barv,"ax",@progbits
.globl  _Z3barv
.type  _Z3barv,@function
_Z3barv:
.Lfunc_begin0:
  .file  0 "/path" "test.cpp" md5 0x9ff11a8404ab4d032ee2dd4f5f8c4140
  .file  1 "test.cpp" md5 0x9ff11a8404ab4d032ee2dd4f5f8c4140
  .loc  1 2 0                   # test.cpp:2:0
  .loc  1 2 20 prologue_end     # test.cpp:2:20
  callq  _Z3foov
  .loc  1 2 13 is_stmt 0        # test.cpp:2:13
.Lfunc_end0:
.size  _Z3barv, .Lfunc_end0-_Z3barv
                                        # -- End function
.section  .text._Z3bazv,"ax",@progbits
.globl  _Z3bazv                 # -- Begin function _Z3bazv
  .type  _Z3bazv,@function
_Z3bazv:                                # @_Z3bazv
.Lfunc_begin1:
  .loc  1 3 0 is_stmt 1         # test.cpp:3:0
  .loc  1 3 20 prologue_end     # test.cpp:3:20
  callq  _Z3foov
  .loc  1 3 13 is_stmt 0        # test.cpp:3:13
.Lfunc_end1:
  .size  _Z3bazv, .Lfunc_end1-_Z3bazv

.section  .debug_str,"MS",@progbits,1
.Linfo_string0:
  .asciz  "stub" 

.section  .debug_str_offsets,"",@progbits
  .long  8
  .short  5
  .short  0
.Lstr_offsets_base0:
  .long  .Linfo_string0

.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  37                      # DW_FORM_strx1
  .byte  19                      # DW_AT_language
  .byte  5                       # DW_FORM_data2
  .byte  3                       # DW_AT_name
  .byte  37                      # DW_FORM_strx1
  .byte  114                     # DW_AT_str_offsets_base
  .byte  23                      # DW_FORM_sec_offset
  .byte  16                      # DW_AT_stmt_list
  .byte  23                      # DW_FORM_sec_offset
  .byte  27                      # DW_AT_comp_dir
  .byte  37                      # DW_FORM_strx1
  .byte  115                     # DW_AT_addr_base
  .byte  23                      # DW_FORM_sec_offset
  .byte  17                      # DW_AT_low_pc
  .byte  1                       # DW_FORM_addr
  .byte  85                      # DW_AT_ranges
  .byte  35                      # DW_FORM_rnglistx
  .byte  116                     # DW_AT_rnglists_base
  .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  27                      # DW_FORM_addrx
  .byte  18                      # DW_AT_high_pc
  .byte  6                       # DW_FORM_data4
  .byte  64                      # DW_AT_frame_base
  .byte  24                      # DW_FORM_exprloc
  .byte  110                     # DW_AT_linkage_name
  .byte  37                      # DW_FORM_strx1
  .byte  3                       # DW_AT_name
  .byte  37                      # DW_FORM_strx1
  .byte  58                      # DW_AT_decl_file
  .byte  11                      # DW_FORM_data1
  .byte  59                      # DW_AT_decl_line
  .byte  11                      # DW_FORM_data1
  .byte  73                      # DW_AT_type
  .byte  19                      # DW_FORM_ref4
  .byte  63                      # DW_AT_external
  .byte  25                      # DW_FORM_flag_present
  .byte  0                       # EOM(1)
  .byte  0                       # EOM(2)
  .byte  3                       # Abbreviation Code
  .byte  36                      # DW_TAG_base_type
  .byte  0                       # DW_CHILDREN_no
  .byte  3                       # DW_AT_name
  .byte  37                      # DW_FORM_strx1
  .byte  62                      # DW_AT_encoding
  .byte  11                      # DW_FORM_data1
  .byte  11                      # DW_AT_byte_size
  .byte  11                      # DW_FORM_data1
  .byte  0                       # EOM(1)
  .byte  0                       # EOM(2)
  .byte  0                       # EOM(3)
  
.section  .debug_info,"",@progbits
.Lcu_begin0:
  .long  .Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
.Ldebug_info_start0:
  .short  5                       # DWARF version number
  .byte  1                       # DWARF Unit Type
  .byte  8                       # Address Size (in bytes)
  .long  .debug_abbrev           # Offset Into Abbrev. Section
  .byte  1                       # Abbrev [1] 0xc:0x44 DW_TAG_compile_unit
  .byte  0                       # DW_AT_producer
  .short  4                       # DW_AT_language
  .byte  0                       # DW_AT_name
  .long  .Lstr_offsets_base0     # DW_AT_str_offsets_base
  .long  .Lline_table_start0     # DW_AT_stmt_list
  .byte  2                       # DW_AT_comp_dir
  .long  0      # DW_AT_addr_base
  .quad  0                       # DW_AT_low_pc
  .byte  0                       # DW_AT_ranges
  .long  0  # DW_AT_rnglists_base
  .byte  2                       # Abbrev [2] 0x2b:0x10 DW_TAG_subprogram
  .byte  0                       # DW_AT_low_pc
  .long  .Lfunc_end0-.Lfunc_begin0 # DW_AT_high_pc
  .byte  1                       # DW_AT_frame_base
  .byte  86
  .byte  3                       # DW_AT_linkage_name
  .byte  0                       # DW_AT_name
  .byte  1                       # DW_AT_decl_file
  .byte  2                       # DW_AT_decl_line
  .long  75                      # DW_AT_type
                                        # DW_AT_external
  .byte  2                       # Abbrev [2] 0x3b:0x10 DW_TAG_subprogram
  .byte  1                       # DW_AT_low_pc
  .long  .Lfunc_end1-.Lfunc_begin1 # DW_AT_high_pc
  .byte  1                       # DW_AT_frame_base
  .byte  86
  .byte  6                       # DW_AT_linkage_name
  .byte  0                       # DW_AT_name
  .byte  1                       # DW_AT_decl_file
  .byte  3                       # DW_AT_decl_line
  .long  75                      # DW_AT_type
                                        # DW_AT_external
  .byte  3                       # Abbrev [3] 0x4b:0x4 DW_TAG_base_type
  .byte  0                       # DW_AT_name
  .byte  5                       # DW_AT_encoding
  .byte  4                       # DW_AT_byte_size
  .byte  0                       # End Of Children Mark
.Ldebug_info_end0:

.section  .debug_line,"",@progbits
.Lline_table_start0:

[avl]

George, Thank you for the comments. I should not rely on context and needed to put detailed description from the scratch. I changed test description and used your compacted asm now.

[grimar]

Thanks, Alexey! This patch looks good to me, but since it was me who suggested to commit it as a separate test for LLD,
I would like somebody else to look and give the final approvement.

Rui, are you OK with it?

[avl]

ping...

[ruiu]

LGTM

lld/test/ELF/debug-line-obj.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux -dwarf-version=5 %s -o %t.o
+# RUN: not ld.lld %t.o -o %t1 2>&1 | FileCheck %s
+
+# Check that LLD correctly reports locations if line number
+# information presented by .debug_line relates to different sections
+# in object file. f.e. if source file compiled with -ffunction-sections
+# flag and addresses are not assigned to sections yet. In that case 
+# .debug_line contains overlapping addresses. 
+
+# CHECK:      error: undefined symbol: foo()
+# CHECK-NEXT: >>> referenced by test.cpp:2
+# CHECK-NEXT: >>>               {{.*}}.o:(bar())
+# CHECK:      error: undefined symbol: foo()
+# CHECK-NEXT: >>> referenced by test.cpp:3
+# CHECK-NEXT: >>>               {{.*}}.o:(baz())
+
+# The code below is the reduced version of the output
+# from the following invocation and source:
+#
+# // test.cpp:
+# int foo();
+# int bar() { return foo(); }
+# int baz() { return foo(); }
+#
+# clang -gdwarf-5 -ffunction-sections test.cpp -o test.s -S
+# clang version 8.0.0 (trunk 343487)
+
+  .text
+  .file "test.cpp"
+  .section  .text._Z3barv,"ax",@progbits
+  .globl  _Z3barv                 # -- Begin function _Z3barv
+  .p2align  4, 0x90
+  .type _Z3barv,@function
+_Z3barv:                                # @_Z3barv
+.Lfunc_begin0:
+  .file 0 "/home/avl/bugs/linker" "test.cpp" md5 0x9ff11a8404ab4d032ee2dd4f5f8c4140
+  .file 1 "test.cpp" md5 0x9ff11a8404ab4d032ee2dd4f5f8c4140
+  .loc  1 2 0                   # test.cpp:2:0
+  .cfi_startproc
+# %bb.0:                                # %entry
+  pushq %rbp
+  .cfi_def_cfa_offset 16
+  .cfi_offset %rbp, -16
+  movq  %rsp, %rbp
+  .cfi_def_cfa_register %rbp
+.Ltmp0:
+  .loc  1 2 20 prologue_end     # test.cpp:2:20
+  callq _Z3foov
+  .loc  1 2 13 is_stmt 0        # test.cpp:2:13
+  popq  %rbp
+  .cfi_def_cfa %rsp, 8
+  retq
+.Ltmp1:
+.Lfunc_end0:
+  .size _Z3barv, .Lfunc_end0-_Z3barv
+  .cfi_endproc
+                                        # -- End function
+  .section  .text._Z3bazv,"ax",@progbits
+  .globl  _Z3bazv                 # -- Begin function _Z3bazv
+  .p2align  4, 0x90
+  .type _Z3bazv,@function
+_Z3bazv:                                # @_Z3bazv
+.Lfunc_begin1:
+  .loc  1 3 0 is_stmt 1         # test.cpp:3:0
+  .cfi_startproc
+# %bb.0:                                # %entry
+  pushq %rbp
+  .cfi_def_cfa_offset 16
+  .cfi_offset %rbp, -16
+  movq  %rsp, %rbp
+  .cfi_def_cfa_register %rbp
+.Ltmp2:
+  .loc  1 3 20 prologue_end     # test.cpp:3:20
+  callq _Z3foov
+  .loc  1 3 13 is_stmt 0        # test.cpp:3:13
+  popq  %rbp
+  .cfi_def_cfa %rsp, 8
+  retq
+.Ltmp3:
+.Lfunc_end1:
+  .size _Z3bazv, .Lfunc_end1-_Z3bazv
+  .cfi_endproc
+                                        # -- End function
+  .section  .debug_str_offsets,"",@progbits
+  .long 36
+  .short  5
+  .short  0
+.Lstr_offsets_base0:
+  .section  .debug_str,"MS",@progbits,1
+.Linfo_string0:
+  .asciz  "clang version 9.0.0 (https://github.com/llvm/llvm-project.git 1081413baa15d9faa1092706468eedddddd8bc35)" # string offset=0
+.Linfo_string1:
+  .asciz  "test.cpp"              # string offset=104
+.Linfo_string2:
+  .asciz  "/home/avl/bugs/linker" # string offset=113
+.Linfo_string3:
+  .asciz  "_Z3barv"               # string offset=135
+.Linfo_string4:
+  .asciz  "bar"                   # string offset=143
+.Linfo_string5:
+  .asciz  "int"                   # string offset=147
+.Linfo_string6:
+  .asciz  "_Z3bazv"               # string offset=151
+.Linfo_string7:
+  .asciz  "baz"                   # string offset=159
+  .section  .debug_str_offsets,"",@progbits
+  .long .Linfo_string0
+  .long .Linfo_string1
+  .long .Linfo_string2
+  .long .Linfo_string3
+  .long .Linfo_string4
+  .long .Linfo_string5
+  .long .Linfo_string6
+  .long .Linfo_string7
+  .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 37                      # DW_FORM_strx1
+  .byte 19                      # DW_AT_language
+  .byte 5                       # DW_FORM_data2
+  .byte 3                       # DW_AT_name
+  .byte 37                      # DW_FORM_strx1
+  .byte 114                     # DW_AT_str_offsets_base
+  .byte 23                      # DW_FORM_sec_offset
+  .byte 16                      # DW_AT_stmt_list
+  .byte 23                      # DW_FORM_sec_offset
+  .byte 27                      # DW_AT_comp_dir
+  .byte 37                      # DW_FORM_strx1
+  .byte 115                     # DW_AT_addr_base
+  .byte 23                      # DW_FORM_sec_offset
+  .byte 17                      # DW_AT_low_pc
+  .byte 1                       # DW_FORM_addr
+  .byte 85                      # DW_AT_ranges
+  .byte 35                      # DW_FORM_rnglistx
+  .byte 116                     # DW_AT_rnglists_base
+  .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 27                      # DW_FORM_addrx
+  .byte 18                      # DW_AT_high_pc
+  .byte 6                       # DW_FORM_data4
+  .byte 64                      # DW_AT_frame_base
+  .byte 24                      # DW_FORM_exprloc
+  .byte 110                     # DW_AT_linkage_name
+  .byte 37                      # DW_FORM_strx1
+  .byte 3                       # DW_AT_name
+  .byte 37                      # DW_FORM_strx1
+  .byte 58                      # DW_AT_decl_file
+  .byte 11                      # DW_FORM_data1
+  .byte 59                      # DW_AT_decl_line
+  .byte 11                      # DW_FORM_data1
+  .byte 73                      # DW_AT_type
+  .byte 19                      # DW_FORM_ref4
+  .byte 63                      # DW_AT_external
+  .byte 25                      # DW_FORM_flag_present
+  .byte 0                       # EOM(1)
+  .byte 0                       # EOM(2)
+  .byte 3                       # Abbreviation Code
+  .byte 36                      # DW_TAG_base_type
+  .byte 0                       # DW_CHILDREN_no
+  .byte 3                       # DW_AT_name
+  .byte 37                      # DW_FORM_strx1
+  .byte 62                      # DW_AT_encoding
+  .byte 11                      # DW_FORM_data1
+  .byte 11                      # DW_AT_byte_size
+  .byte 11                      # DW_FORM_data1
+  .byte 0                       # EOM(1)
+  .byte 0                       # EOM(2)
+  .byte 0                       # EOM(3)
+  .section  .debug_info,"",@progbits
+.Lcu_begin0:
+  .long .Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
+.Ldebug_info_start0:
+  .short  5                       # DWARF version number
+  .byte 1                       # DWARF Unit Type
+  .byte 8                       # Address Size (in bytes)
+  .long .debug_abbrev           # Offset Into Abbrev. Section
+  .byte 1                       # Abbrev [1] 0xc:0x44 DW_TAG_compile_unit
+  .byte 0                       # DW_AT_producer
+  .short  4                       # DW_AT_language
+  .byte 1                       # DW_AT_name
+  .long .Lstr_offsets_base0     # DW_AT_str_offsets_base
+  .long .Lline_table_start0     # DW_AT_stmt_list
+  .byte 2                       # DW_AT_comp_dir
+  .long .Laddr_table_base0      # DW_AT_addr_base
+  .quad 0                       # DW_AT_low_pc
+  .byte 0                       # DW_AT_ranges
+  .long .Lrnglists_table_base0  # DW_AT_rnglists_base
+  .byte 2                       # Abbrev [2] 0x2b:0x10 DW_TAG_subprogram
+  .byte 0                       # DW_AT_low_pc
+  .long .Lfunc_end0-.Lfunc_begin0 # DW_AT_high_pc
+  .byte 1                       # DW_AT_frame_base
+  .byte 86
+  .byte 3                       # DW_AT_linkage_name
+  .byte 4                       # DW_AT_name
+  .byte 1                       # DW_AT_decl_file
+  .byte 2                       # DW_AT_decl_line
+  .long 75                      # DW_AT_type
+                                        # DW_AT_external
+  .byte 2                       # Abbrev [2] 0x3b:0x10 DW_TAG_subprogram
+  .byte 1                       # DW_AT_low_pc
+  .long .Lfunc_end1-.Lfunc_begin1 # DW_AT_high_pc
+  .byte 1                       # DW_AT_frame_base
+  .byte 86
+  .byte 6                       # DW_AT_linkage_name
+  .byte 7                       # DW_AT_name
+  .byte 1                       # DW_AT_decl_file
+  .byte 3                       # DW_AT_decl_line
+  .long 75                      # DW_AT_type
+                                        # DW_AT_external
+  .byte 3                       # Abbrev [3] 0x4b:0x4 DW_TAG_base_type
+  .byte 5                       # DW_AT_name
+  .byte 5                       # DW_AT_encoding
+  .byte 4                       # DW_AT_byte_size
+  .byte 0                       # End Of Children Mark
+.Ldebug_info_end0:
+  .section  .debug_rnglists,"",@progbits
+  .long .Ldebug_rnglist_table_end0-.Ldebug_rnglist_table_start0 # Length
+.Ldebug_rnglist_table_start0:
+  .short  5                       # Version
+  .byte 8                       # Address size
+  .byte 0                       # Segment selector size
+  .long 1                       # Offset entry count
+.Lrnglists_table_base0:
+  .long .Ldebug_ranges0-.Lrnglists_table_base0
+.Ldebug_ranges0:
+  .byte 3                       # DW_RLE_startx_length
+  .byte 0                       #   start index
+  .uleb128 .Lfunc_end0-.Lfunc_begin0 #   length
+  .byte 3                       # DW_RLE_startx_length
+  .byte 1                       #   start index
+  .uleb128 .Lfunc_end1-.Lfunc_begin1 #   length
+  .byte 0                       # DW_RLE_end_of_list
+.Ldebug_rnglist_table_end0:
+.Ldebug_addr_start0:
+  .short  5                       # DWARF version number
+  .byte 8                       # Address size
+  .byte 0                       # Segment selector size
+.Laddr_table_base0:
+  .quad .Lfunc_begin0
+  .quad .Lfunc_begin1
+.Ldebug_addr_end0:
+
+  .section  .debug_line,"",@progbits
+.Lline_table_start0: