[LLVMdev] Proposal: add Go frontend subproject based on llgo

[Ian Taylor]

On Wed, Nov 19, 2014 at 4:58 PM, Peter Collingbourne <peter at pcc.me.uk> wrote:
> On Thu, Nov 20, 2014 at 12:19:06AM +0100, Joerg Sonnenberger wrote:
>> On Wed, Nov 19, 2014 at 01:53:17PM -0800, Peter Collingbourne wrote:
>> > llgo depends on certain third-party components, namely a copy of the Go
>> > standard library (libgo), a Go program analysis library (go.tools) and two
>> > library dependencies of the standard library (libbacktrace and libffi).
>>
>> I think providing a better alternative to libffi is already a goal of
>> some people, but what is libbacktrace needed for? What is not provided
>> by the Itanium Unwind ABI?
>
> According to the libbacktrace readme file:
>
>> As of September 2012, libbacktrace only supports ELF executables with
>> DWARF debugging information.  The library is written to make it
>> straightforward to add support for other object file and debugging
>> formats.
>
> Ian (the author of libbacktrace) may be able to provide more context.

I'm not sure I know the context for which I am providing context.
That said, libbacktrace is not an instantiation of the unwind ABI, it
is a client.  The unwind ABI gives you a call stack but only provides
PC and SP values.  libbacktrace gives you function names, file names,
and line numbers.  It does this by reading the debug info at runtime;
at present it only supports DWARF.

Ian