Filename's in DIBuileder

Hi All ,

We have a scenario in our debugger to handle the file index in the debug_ine info like

$llvm-dwarfdump -debug-line test.o
file_names[ 1]:
name: “test.cpp”
dir_index: 0
mod_time: 0x00000000
length: 0x00000000
file_names[ 2]:
name: “test.cpp”
dir_index: 1
mod_time: 0x00000000
length: 0x00000000

Address Line Column File ISA Discriminator Flags


0x0000000000000000 12 0 1 0 0 is_stmt
0x0000000000000008 13 1 1 0 0 is_stmt prologue_end
0x0000000000000010 16 0 1 0 0 is_stmt
0x0000000000000018 17 1 1 0 0 is_stmt prologue_end
0x0000000000000020 20 0 1 0 0 is_stmt
0x0000000000000028 21 9 1 0 0 is_stmt prologue_end
0x000000000000002f 22 9 1 0 0 is_stmt
0x0000000000000032 22 10 1 0 0
0x0000000000000035 22 7 1 0 0
0x000000000000003c 23 1 1 0 0 is_stmt
0x0000000000000040 25 0 1 0 0 is_stmt
0x0000000000000044 25 13 1 0 0 is_stmt prologue_end
0x0000000000000080 0 0 2 0 0 is_stmt
0x000000000000008b 0 0 2 0 0 is_stmt end_sequence

the debug info is emitted by the DIBuilder like

!3 = !DIFile(filename: “/folk/tmp/test/test.cpp”, directory: “/folk/tmp/test”)
!45 = distinct !DISubprogram(linkageName: “_GLOBAL__sub_I_test.cpp”, scope: !3, file: !3, type: !46, flags: DIFlagArtificial, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition, unit: !2, retainedNodes: !4)

!8 = !DIFile(filename: “test.cpp”, directory: “/folk/tmp/test”)
!16 = !DISubprogram(name: “proc”, linkageName: “_ZN4test4procEv”, scope: !9, file: !8, line: 8, type: !12, scopeLine: 8, flags: DIFlagPublic | DIFlagPrototyped, spFlags: 0)

Latest clang trunk used like

$clang -std=c++14 -g -eimit-llvm -S /folk/tmp/test/test.cpp

and the respective files like test.cc ,test.ll and test.s are attached in the mail for the reference.

the scenario is that why the file-name 's are different is both cases ,where “ZN4test4procEv” is the user defined function and “_GLOBAL__sub_I_test.cpp”
is generated for the static initialisation ,which leads to the two file index like 1 and 2 for two files in the filename table ,that confuse our debugger .

So we like to hear from experts here ,before we investigate the DIBuilder to fix the same.

Thank you
~Umesh

test.cpp (229 Bytes)

test.ll (8.57 KB)

test.s (24.3 KB)

[AMD Official Use Only - Internal Distribution Only]

Didn’t observed this on trunk(Using attached test.cpp): Trunk at 29ae4485950ed76faa94dabbd13bbe91d2b5c750

$clang++ -std=c++14 -g test.cpp -c -S -emit-llvm -o - | awk /DIFile/

!3 = !DIFile(filename: “test.cpp”, directory: “/home/”)

$ clang++ -std=c++14 -g test.cpp -c -o - | llvm-dwarfdump -debug-line -

[…]

file_names[ 1]:

name: “test.cpp”

dir_index: 0

mod_time: 0x00000000

length: 0x00000000

[…]

Did I missed something, while reproducing ? ?

–Sourabh

Try using $PWD/test.cpp on the clang command line. I am seeing the duplicate DIFile entries, but not yet able to reproduce a .debug_line section with multiple directory entries.

–paulr

Aha. The two DIFile entries are describing the same file two different ways, but the file-tracking is not noticing that the two descriptions are equivalent. And I am convinced it is because the compilation command uses an absolute path.

This could be a failure to deduplicate the file entries in the frontend, or a similar failure in MC once it starts handing out file numbers. (Possibly both!)

Umesh, could you file a bug for this (at https://bugs.llvm.org) please? Use product “libraries” component “DebugInfo” and the right people will see it. (It is quite possibly my fault…) This might be a duplicate of an existing bug, but we can figure that out later.

Thanks!

–paulr

[AMD Official Use Only - Internal Distribution Only]

Thanks Paul.
It’s reproducible both DIFile and debug_line(multiple directory entries).

$tot-clang++ -g $PWD/test.cpp -c -o - | llvm-dwarfdump -debug-line –

[…]
include_directories[ 1] = “/home/”

file_names[ 1]:

name: “test.cpp”

dir_index: 0

mod_time: 0x00000000

length: 0x00000000

file_names[ 2]:

name: “test.cpp”

dir_index: 1

mod_time: 0x00000000

length: 0x00000000

[…]

–Sourabh

[AMD Official Use Only - Internal Distribution Only]

This behavior(line table entries) is not seen with “C” test case:

$tot-clang -g $PWD/main.c -emit-llvm -S -o - | awk /DIFile/

!1 = !DIFile(filename: “/home/main.c”, directory: “/home/”)

!8 = !DIFile(filename: “main.c”, directory: “/home/”)

$tot-clang -g $PWD/main.c -c -o - | llvm-dwarfdump -debug-line –

[…]

file_names[ 1]:

name: “main.c”

dir_index: 0

mod_time: 0x00000000

length: 0x00000000

[…]

–Sourabh

[AMD Official Use Only - Internal Distribution Only]

This behavior(line table entries) is not seen with “C” test case:

$tot-clang -g $PWD/main.c -emit-llvm -S -o - | awk /DIFile/

!1 = !DIFile(filename: “/home/main.c”, directory: “/home/”)

!8 = !DIFile(filename: “main.c”, directory: “/home/”)

$tot-clang -g $PWD/main.c -c -o - | llvm-dwarfdump -debug-line –

[…]

file_names[ 1]:

name: “main.c”

dir_index: 0

mod_time: 0x00000000

length: 0x00000000

[…]

–Sourabh

Thank you Paual and Tomar .

https://bugs.llvm.org/show_bug.cgi?id=47391

FYI ,
Two entries for the same file are handled by gnu assembler .

~Umesh