[lld] r333880 - [ELF] - Also use DW_AT_linkage_name when gathering information about variables for error messages.
George Rimar via llvm-commits
llvm-commits at lists.llvm.org
Mon Jun 18 07:20:12 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.
Hi David,
My apologies for the belated response here (I had a vacation).
Idea of using dwarfdump was to demonstrate readers that we have 2 variables with the same DW_AT_name and different
DW_AT_linkage_name. Though I agree it was excessive here since I am using the full asm code with explicit values
of strings to produce inputs anyways.
Fixed in https://reviews.llvm.org/rL334946, thanks!
On Mon, Jun 4, 2018 at 3:32 AM George Rimar via llvm-commits <llvm-commits at lists.llvm.org<mailto: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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