[llvm-bugs] [Bug 41886] New: -d/-r/-j should not require relocation sections be specified with -j

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=41886

            Bug ID: 41886
           Summary: -d/-r/-j should not require relocation sections be
                    specified with -j
           Product: tools
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: llvm-objdump
          Assignee: unassignedbugs at nondot.org
          Reporter: jh7370.2008 at my.bristol.ac.uk
                CC: llvm-bugs at lists.llvm.org

llvm-objdump -d -r prints relocations inline with the disassembly as follows:

C:\> llvm-objdump -d -r test.o

Disassembly of section .text:

0000000000000400 .text:
     400: e8 00 00 00 00                callq   0 <.text+0x5>
                0000000000000401:  R_X86_64_PC32        foo+1
                0000000000000401:  R_X86_64_GOT32       foo

Disassembly of section .text2:

0000000000000401 .text2:
     401: 90                            nop
     402: e8 00 00 00 00                callq   0 <.text2+0x6>
                0000000000000402:  R_X86_64_PLT32       foo+2

This is the same behaviour as GNU objdump. However, if you apply --section, the
behaviour differs. --section for GNU objdump reduces the disassembly down to
the listed sections, and prints all the relocations for those sections (note,
the below output is approximate, and not exactly what GNU objdump prints, but
is used for illustration purposes):

C:\> objdump -d -r test.o --section .text

Disassembly of section .text:

0000000000000400 .text:
     400: e8 00 00 00 00                callq   0 <.text+0x5>
                0000000000000401:  R_X86_64_PC32        foo+1 //from .rela.text
                0000000000000401:  R_X86_64_GOT32       foo   //from
.rela2.text

llvm-objdump only prints the relocations that come from the listed relocations:

C:\> llvm-objdump -d -r test.o --section .text

Disassembly of section .text:

0000000000000400 .text:
     400: e8 00 00 00 00                callq   0 <.text+0x5>
// No relocations printed

C:\> llvm-objdump -d -r test.o --section .text --rela.text

Disassembly of section .text:

0000000000000400 .text:
     400: e8 00 00 00 00                callq   0 <.text+0x5>
                0000000000000401:  R_X86_64_PC32        foo+1 //from .rela.text

Intuitively, I didn't expect llvm-objdump to behave the way it does, even
without coming from a GNU background. The behaviour is subtle and could easily
break users. I think we should change the behaviour to match GNU and always
print the relocations for the sections that are disassembled, not just the
filtered set of relocations.

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