[LLVMdev] Debug info failing in assembler.

[Richard Mitton]

If it thinks the symbol is in the BSS section, then it should never have 
tried to use .comm to emit it I think.

On x86 it does not try to mix and match, which is why it works. AFAIK 
comm symbols are regarded as having no section, rather than being bss, 
so I think it's a bug in whatever code printed that .comm statement.

I'll look into this tomorrow.

> Eric Christopher <mailto:echristo at gmail.com>
> Saturday, September 21, 2013 11:26 AM
>
> Interesting. File please? Thanks.
>
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> Richard Pennington <mailto:rich at pennware.com>
> Saturday, September 21, 2013 5:52 AM
> Hi,
>
> I just updated from r190763 to r191137 and started getting failures in 
> generated assembly language when debug info is enabled. Here is the 
> test case:
>
> // Compile and run for every target.
> // RUN: %ecc -g -o %t %s && %t
> // FAIL: %armecc -g -o %t %s && %armrun %t
> // FAIL: %armebecc -g -o %t %s && %armebrun %t
> // RUN: %i386ecc -g -o %t %s && %i386run %t
> // FAIL: %microblazeecc -g -o %t %s && %microblazerun %t
> // FAIL: %mipsecc -g -o %t %s && %mipsrun %t
> // FAIL: %mipselecc -g -o %t %s && %mipselrun %t
> // FAIL: %ppcecc -g -o %t %s && %ppcrun %t
> // FAIL: %ppc64ecc -g -o %t %s && %ppc64run %t
> // RUN: %x86_64ecc -g -o %t %s && %x86_64run %t
>
> int comm;
> int main()
> {
>     comm = 6;
> }
>
> This fails on all but the x86 processors. The typical failure looks 
> like this:
> ...
>         .type   comm, at object            # @comm
>         .comm   comm,4,4
>         .cfi_sections .debug_frame
>         .bss
> .L.bss_end:
> ...
> .L.debug_abbrev_end:
>         .section        .debug_aranges,"", at progbits
>         .long   36                      # Length of ARange Set
>         .short  2                       # DWARF Arange version number
>         .long   .L.debug_info_begin0    # Offset Into Debug Info Section
>         .byte   4                       # Address Size (in bytes)
>         .byte   0                       # Segment Size (in bytes)
>         .byte   255
>         .byte   255
>         .byte   255
>         .byte   255
>         .long   comm
> .Lset0 = .L.bss_end-comm
>         .long   .Lset0
>
> The typical error message is:
> /tmp/debug-8ecf9d.s: Assembler messages:
> /tmp/debug-8ecf9d.s: Error: invalid operands (.bss and *COM* sections) 
> for `-' when setting `.Lset0'
>
> Is it legal to mix .comm symbols and .bss symbols in assembly? Is the 
> x86 success a bug or a feature?
>
> -Rich
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