[lld] r333880 - [ELF] - Also use DW_AT_linkage_name when gathering information about variables for error messages.
David Blaikie via llvm-commits
llvm-commits at lists.llvm.org
Mon Jun 4 09:25:11 PDT 2018
I'm not sure it's really necessary to test the dwarfdump - if we're
assuming/modelling these sort of tests as "MC is trivially correct" (ie:
we're not testing MC here, using it as a convenient tool for generating
binary inputs) then there's no need to test its output here & I'd probably
skip that testing here. MC is already tested elsewhere.
On Mon, Jun 4, 2018 at 3:32 AM George Rimar via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> Author: grimar
> Date: Mon Jun 4 03:28:45 2018
> New Revision: 333880
>
> URL: http://llvm.org/viewvc/llvm-project?rev=333880&view=rev
> Log:
> [ELF] - Also use DW_AT_linkage_name when gathering information about
> variables for error messages.
>
> Currently, when LLD do a lookup for variables location, it uses DW_AT_name
> attribute.
> That is not always enough.
>
> Imagine code:
>
> namespace A {
> int bar = 0;
> }
>
> namespace Z {
> int bar = 1;
> }
>
> int hoho;
> In this case there are 3 variables and their debug attributes are
> following:
>
> A::bar has: DW_AT_name [DW_FORM_string] ("bar") DW_AT_linkage_name
> [DW_FORM_strp] ( .debug_str[0x00000006] = "_ZN1A3barE")
> Z::bar has: DW_AT_name [DW_FORM_string] ("bar") DW_AT_linkage_name
> [DW_FORM_strp] ( .debug_str[0x0000003f] = "_ZN1Z3barE")
> hoho has: DW_AT_name [DW_FORM_strp] ( .debug_str[0x0000004a] = "hoho") and
> has NO DW_AT_linkage_name attribute. Because it would be
> the same as DW_AT_name and DWARF producers avoids emiting excessive data.
>
> Hence LLD should also use DW_AT_linkage_name when it is available.
> (currently, LLD fails to report location correctly because thinks that
> A::bar and Z::bar are the same things)
>
> Differential revision: https://reviews.llvm.org/D47373
>
> Added:
> lld/trunk/test/ELF/conflict-variable-linkage-name.s
> Modified:
> lld/trunk/ELF/InputFiles.cpp
>
> Modified: lld/trunk/ELF/InputFiles.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputFiles.cpp?rev=333880&r1=333879&r2=333880&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/InputFiles.cpp (original)
> +++ lld/trunk/ELF/InputFiles.cpp Mon Jun 4 03:28:45 2018
> @@ -167,10 +167,15 @@ template <class ELFT> void ObjFile<ELFT>
> // Get the line number on which the variable is declared.
> unsigned Line = dwarf::toUnsigned(Die.find(dwarf::DW_AT_decl_line),
> 0);
>
> - // Get the name of the variable and add the collected information to
> - // VariableLoc. Usually Name is non-empty, but it can be empty if
> the
> + // Here we want to take the variable name to add it into
> VariableLoc.
> + // Variable can have regular and linkage name associated. At first,
> we try
> + // to get linkage name as it can be different, for example when we
> have
> + // two variables in different namespaces of the same object. Use
> common
> + // name otherwise, but handle the case when it also absent in case
> if the
> // input object file lacks some debug info.
> - StringRef Name = dwarf::toString(Die.find(dwarf::DW_AT_name), "");
> + StringRef Name =
> + dwarf::toString(Die.find(dwarf::DW_AT_linkage_name),
> + dwarf::toString(Die.find(dwarf::DW_AT_name),
> ""));
> if (!Name.empty())
> VariableLoc.insert({Name, {LT, File, Line}});
> }
>
> Added: lld/trunk/test/ELF/conflict-variable-linkage-name.s
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/conflict-variable-linkage-name.s?rev=333880&view=auto
>
> ==============================================================================
> --- lld/trunk/test/ELF/conflict-variable-linkage-name.s (added)
> +++ lld/trunk/test/ELF/conflict-variable-linkage-name.s Mon Jun 4
> 03:28:45 2018
> @@ -0,0 +1,193 @@
> +# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
> +# RUN: llvm-dwarfdump %t.o | FileCheck -check-prefix=INPUT %s
> +# RUN: not ld.lld %t.o %t.o -o %t 2>&1 | FileCheck %s
> +
> +# INPUT: DW_TAG_variable
> +# INPUT-NEXT: DW_AT_name ("bar")
> +# INPUT-NEXT: DW_AT_type (0x0000003d "int")
> +# INPUT-NEXT: DW_AT_external (true)
> +# INPUT-NEXT: DW_AT_decl_file ("/path\1.cpp")
> +# INPUT-NEXT: DW_AT_decl_line (2)
> +# INPUT-NEXT: DW_AT_location (DW_OP_addr 0x0)
> +# INPUT-NEXT: DW_AT_linkage_name ("_ZN1A3barE")
> +# INPUT: DW_TAG_variable
> +# INPUT-NEXT: DW_AT_name ("bar")
> +# INPUT-NEXT: DW_AT_type (0x0000003d "int")
> +# INPUT-NEXT: DW_AT_external (true)
> +# INPUT-NEXT: DW_AT_decl_file ("/path\1.cpp")
> +# INPUT-NEXT: DW_AT_decl_line (6)
> +# INPUT-NEXT: DW_AT_location (DW_OP_addr 0x0)
> +# INPUT-NEXT: DW_AT_linkage_name ("_ZN1Z3barE")
> +
> +## Check we can report the locations of 2 different "bar" variables.
> +# CHECK: duplicate symbol: A::bar
> +# CHECK-NEXT: >>> defined at 1.cpp:2
> +# CHECK-NEXT: >>> {{.*}}:(A::bar)
> +# CHECK-NEXT: >>> defined at 1.cpp:2
> +# CHECK-NEXT: >>> {{.*}}:(.bss+0x0)
> +# CHECK: duplicate symbol: Z::bar
> +# CHECK-NEXT: >>> defined at 1.cpp:6
> +# CHECK-NEXT: >>> {{.*}}:(Z::bar)
> +# CHECK-NEXT: >>> defined at 1.cpp:6
> +# CHECK-NEXT: >>> {{.*}}:(.data+0x0)
> +
> +# Used reduced output from following code and clang version 7.0.0 (trunk
> 332701)
> +# to produce this input file:
> +# Source (1.cpp):
> +# namespace A {
> +# int bar;
> +# }
> +#
> +# namespace Z {
> +# int bar;
> +# }
> +# Invocation: clang-7 -g -S 1.cpp
> +
> +.text
> +.file "1.cpp"
> +.file 1 "/path" "1.cpp"
> +
> +.type _ZN1A3barE, at object
> +.bss
> +.globl _ZN1A3barE
> +_ZN1A3barE:
> + .long 0
> + .size _ZN1A3barE, 4
> +
> +.type _ZN1Z3barE, at object
> +.data
> +.globl _ZN1Z3barE
> +_ZN1Z3barE:
> + .long 1
> + .size _ZN1Z3barE, 4
> +
> +.section .debug_str,"MS", at progbits,1
> +.Linfo_string0:
> + .asciz "clang version 7.0.0 (trunk 332701)" # string offset=0
> +.Linfo_string1:
> + .asciz "1.cpp" # string offset=35
> +.Linfo_string2:
> + .asciz "/path" # string offset=41
> +.Linfo_string3:
> + .asciz "A" # string offset=87
> +.Linfo_string4:
> + .asciz "bar" # string offset=89
> +.Linfo_string5:
> + .asciz "int" # string offset=93
> +.Linfo_string6:
> + .asciz "_ZN1A3barE" # string offset=97
> +.Linfo_string7:
> + .asciz "Z" # string offset=108
> +.Linfo_string8:
> + .asciz "_ZN1Z3barE" # string offset=110
> +
> +.section .debug_abbrev,"", at 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
> + .ascii "\264B" # DW_AT_GNU_pubnames
> + .byte 25 # DW_FORM_flag_present
> + .byte 0 # EOM(1)
> + .byte 0 # EOM(2)
> +
> + .byte 2 # Abbreviation Code
> + .byte 57 # DW_TAG_namespace
> + .byte 1 # DW_CHILDREN_yes
> + .byte 3 # DW_AT_name
> + .byte 14 # DW_FORM_strp
> + .byte 0 # EOM(1)
> + .byte 0 # EOM(2)
> +
> + .byte 3 # Abbreviation Code
> + .byte 52 # DW_TAG_variable
> + .byte 0 # DW_CHILDREN_no
> + .byte 3 # DW_AT_name
> + .byte 14 # DW_FORM_strp
> + .byte 73 # DW_AT_type
> + .byte 19 # DW_FORM_ref4
> + .byte 63 # DW_AT_external
> + .byte 25 # DW_FORM_flag_present
> + .byte 58 # DW_AT_decl_file
> + .byte 11 # DW_FORM_data1
> + .byte 59 # DW_AT_decl_line
> + .byte 11 # DW_FORM_data1
> + .byte 2 # DW_AT_location
> + .byte 24 # DW_FORM_exprloc
> + .byte 110 # DW_AT_linkage_name
> + .byte 14 # DW_FORM_strp
> + .byte 0 # EOM(1)
> + .byte 0 # EOM(2)
> +
> + .byte 4 # Abbreviation Code
> + .byte 36 # DW_TAG_base_type
> + .byte 0 # DW_CHILDREN_no
> + .byte 3 # DW_AT_name
> + .byte 14 # DW_FORM_strp
> + .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,"", at progbits
> + .long 96 # 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:0x59 DW_TAG_compile_unit
> + .long .Linfo_string0 # DW_AT_producer
> + .short 4 # DW_AT_language
> + .long .Linfo_string1 # DW_AT_name
> + .long 0 # DW_AT_stmt_list
> + .long .Linfo_string2 # DW_AT_comp_dir
> + # DW_AT_GNU_pubnames
> +
> + .byte 2 # Abbrev [2] 0x1e:0x1f DW_TAG_namespace
> + .long .Linfo_string3 # DW_AT_name
> +
> + .byte 3 # Abbrev [3] 0x23:0x19 DW_TAG_variable
> + .long .Linfo_string4 # DW_AT_name
> + .long 61 # DW_AT_type
> + # DW_AT_external
> + .byte 1 # DW_AT_decl_file
> + .byte 2 # DW_AT_decl_line
> + .byte 9 # DW_AT_location
> + .byte 3
> + .quad _ZN1A3barE
> + .long .Linfo_string6 # DW_AT_linkage_name
> + .byte 0 # End Of Children Mark
> +
> + .byte 4 # Abbrev [4] 0x3d:0x7 DW_TAG_base_type
> + .long .Linfo_string5 # DW_AT_name
> + .byte 5 # DW_AT_encoding
> + .byte 4 # DW_AT_byte_size
> +
> + .byte 2 # Abbrev [2] 0x44:0x1f DW_TAG_namespace
> + .long .Linfo_string7 # DW_AT_name
> +
> + .byte 3 # Abbrev [3] 0x49:0x19 DW_TAG_variable
> + .long .Linfo_string4 # DW_AT_name
> + .long 61 # DW_AT_type
> + # DW_AT_external
> + .byte 1 # DW_AT_decl_file
> + .byte 6 # DW_AT_decl_line
> + .byte 9 # DW_AT_location
> + .byte 3
> + .quad _ZN1Z3barE
> + .long .Linfo_string8 # DW_AT_linkage_name
> +
> + .byte 0 # End Of Children Mark
> + .byte 0 # End Of Children Mark
>
>
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