[llvm-bugs] [Bug 32775] New: LLD/COFF should not allow absolute symbols to be exported

[via llvm-bugs]

http://bugs.llvm.org/show_bug.cgi?id=32775

            Bug ID: 32775
           Summary: LLD/COFF should not allow absolute symbols to be
                    exported
           Product: lld
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: COFF
          Assignee: unassignedbugs at nondot.org
          Reporter: peter at pcc.me.uk
                CC: llvm-bugs at lists.llvm.org

I don't think it's possible to represent an exported absolute symbol in the PE
format because all exported RVAs are adjusted to the image base. And indeed,
the MSVC linker rejects attempts to do so:

>type 2.s
.globl  i
i = 42

>\src\llvm-project\ra\bin\llvm-mc -filetype=obj -o 2.obj 2.s

>link /dll /export:i 2.obj /defaultlib:libcmt
Microsoft (R) Incremental Linker Version 14.00.24215.1
Copyright (C) Microsoft Corporation.  All rights reserved.

   Creating library 2.lib and object 2.exp
2.exp : error LNK2016: absolute symbol 'i' used as target of ADDR32NB
relocation in section 1
LINK : fatal error LNK1165: link failed because of fixup errors

But we don't:

>..\llvm-project\ra\bin\lld-link /dll /export:i 2.obj /defaultlib:libcmt

And we create a bogus RVA:

>dumpbin /exports 2.dll
Microsoft (R) COFF/PE Dumper Version 14.00.24215.1
Copyright (C) Microsoft Corporation.  All rights reserved.


Dump of file 2.dll

File Type: DLL

  Section contains the following exports for 2.dll

    00000000 characteristics
           0 time date stamp
        0.00 version
           0 ordinal base
           2 number of functions
           1 number of names

    ordinal hint RVA      name

          1    0 8000002A i

  Summary

        1000 .00cfg
        2000 .bss
        1000 .data
        1000 .edata
        1000 .gfids
        1000 .idata
        1000 .pdata
        7000 .rdata
        1000 .reloc
        B000 .text
        2000 .xdata

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