[Bug gas/26143] gas generates invalid line table entry

[nickc at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26143

Nick Clifton <nickc at redhat dot com> changed:

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                 CC|                            |nickc at redhat dot com

--- Comment #1 from Nick Clifton <nickc at redhat dot com> ---
(In reply to Tom de Vries from comment #0)
Hi Tom,

>   [0x00000080]  Special opcode 75: advance Address by 5 to 0x1c and Line by
> 0 to 12
>   [0x00000081]  Extended opcode 1: End of Sequence

> Every line number program sequence must end with a DW_LNE_end_sequence
> instruction which creates a row whose address is that of the byte after the
> last target machine instruction of the sequence.

> One the one hand, the end-of-sequence declares that address 0x1c is one past
> the byte of the last target machine instruction of the sequence.
> 
> On the other hand, the special opcode declares a target instruction starting
> at address 0x1c, that is part of that same sequence.

Ah - but special opcodes do not necessarily assert that there is a target
instruction starting at the address they reference.  


>     This option causes a row to be added to .debug_line in reference to the
> current address (which might not be the same as that of the following
> assembly instruction),  

> I cannot tell from the formulation "in reference to the current address
> (which might not be the same as that of the following assembly instruction)"
> whether this particular instance of .loc usage is valid.

My take on this is that the "view" directive specifies a property for an
address, but it does not require that there be an instruction at that address. 
Hence the generated line number table is correct...

Cheers
  Nick

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