[lldb-dev] Host::GetArchitecture and the default target triple

[Matthew Gardiner]

Hi Zachary,

I'm not sure whether what I'm going to say is relevant to your current 
quest, but I can see that you're doing a lot of refactoring, and that 
you mentioned the Triple stuff. It took me sometime to get CSRs Kalimba 
processors vaguely debuggable using lldb. A lot of my struggle was in 
the Triple/ArchSpec area... I thought just mention that our kalimbas run 
bare-metal (no OS) so when you any refactoring, please be sure that the 
UnknownOS cases still work!

Apologies if my post is dreadfully off-target, but when the word triple 
was mentioned, I thought that I should pipe up.

thanks
Matt


Zachary Turner wrote:
> Ok. So it looks like x86_64h is not currently supported by 
> llvm::Triple.  I will find out about adding support for it.  If it's 
> possible to get that into llvm::Triple, I'll post a patch that updates 
> Host::GetArchitecture() to use it, and then maybe one of you guys can 
> test it in the various configurations.
>
> Thanks!
>
>
> On Tue, Aug 19, 2014 at 2:18 PM, <jingham at apple.com 
> <mailto:jingham at apple.com>> wrote:
>
>     Sorry, I didn't read closely enough.  Greg's answer is actually
>     relevant to your question...
>
>     Jim
>
>     > On Aug 19, 2014, at 2:04 PM, Zachary Turner <zturner at google.com
>     <mailto:zturner at google.com>> wrote:
>     >
>     > In this case though, we're talking about Host::GetArchitecture,
>     which is a static function and is supposed to report information
>     about the OS that the debugger is running on, and not the target
>     that the debuggee is running on.  Does this mean that a single
>     instance of LLDB cannot debug both an app running in the
>     simulator, and an app running in darwin?  So you have to exit LLDB
>     and start a new instance of LLDB in "simulator mode" or "mac
>     mode"?  Or am I misunderstanding?
>     >
>     >
>     > On Tue, Aug 19, 2014 at 1:58 PM, <jingham at apple.com
>     <mailto:jingham at apple.com>> wrote:
>     > Mac OS X is more complex because lldb also supports apps running
>     in the iOS simulator on OS X.  Those apps are x86 or x86_64
>     processes, but their OS is "ios", not "darwin".  The platforms and
>     a bunch of other fiddly bits rely on getting the OS right as well.
>     >
>     > Jim
>     >
>     > > On Aug 19, 2014, at 1:52 PM, Zachary Turner
>     <zturner at google.com <mailto:zturner at google.com>> wrote:
>     > >
>     > > Looking over the apple code path for Host::GetArchitecture,
>     I'm a little confused about why all this custom logic is needed. 
>     What are the situations in which
>     llvm::sys::getDefaultTargetTriple() will return something other
>     than what we want? Specifically, a concrete example might help
>     illustrate the problem.
>     > >
>     > > I understand from the comment that it has something to do with
>     being able to run 32 and 64-bit executables in the same operating
>     system.  Isn't this the case everywhere?  I can run 32-bit
>     executables on Windows x64 as well.  llvm::Triple has a function
>     called get32BitArchVariant() that I thought returns a 32-bit
>     triple for this case.  Does this not work for some Apple
>     configuration?
>     > >
>     > > It seems like this logic should be able to be sunk into
>     llvm::Triple somehow.  Conceptually speaking, it seems like there
>     should be two cases:
>     > >
>     > > 64-bit:
>     > > host_arch_64 = llvm::Triple::getDefaultTargetTriple()
>     > > host_arch_32 =
>     llvm::Triple::getDefaultTargetTriple().get32BitArchVariant()
>     > >
>     > > 32-bit
>     > > host_arch_64 = <empty>
>     > > host_arch_32 = llvm::Triple::getDefaultTargetTriple()
>     > >
>     > > Why doesn't this work?
>     > > _______________________________________________
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>     >
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