[Bug binutils/19446] New: BFD linker discards section without alloc section attribute under certain conditions

[xinliangli at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19446

            Bug ID: 19446
           Summary: BFD linker discards section without alloc section
                    attribute under certain conditions
           Product: binutils
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: binutils
          Assignee: unassigned at sourceware dot org
          Reporter: xinliangli at gmail dot com
  Target Milestone: ---

If a section is not marked with SHF_ALLOC attribute and when --gc-sections is
on, the BFD linker only keeps it if the section has no references to other
symbols. If there is reference to other symbols, the linker will garbage
collect it.

By comparison, Gold linker does not garbage collect such sections regardless of
the contents of the section.

Example:  t.s

gcc -fuse-ld=bfd -Wl,--gc-sections t.s

objdump -h a.out |grep UNREF

Changing the assembly file a little by making unref initialized to 0, linker
will keep the UNREF section.

The version of the linker tested is 2.24.

        .file   "unref2.c"
        .comm   g0,4,4

        .globl  unref
        .section        UNREF,"",@progbits
        .align 8
        .type   unref, @object
        .size   unref, 8
unref:
        .quad   g0

        .text
        .globl  main
        .type   main, @function
main:
.LFB0:
        .cfi_startproc
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
        movl    $1, %eax
        popq    %rbp
        .cfi_def_cfa 7, 8
        ret
        .cfi_endproc
.LFE0:
        .size   main, .-main
        .ident  "GCC: (Ubuntu 4.8.4-2ubuntu1~14.04) 4.8.4"
        .section        .note.GNU-stack,"",@progbits

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