Hi all,
Yahoo, happy news -- I think I've got it. Studying enough of the
non-handwritten ASM that I was stepping through led me to make this change:
https://github.com/lukexi/ghc/commit/1140e11db07817fcfc12446c74cd5a2bcdf9278...
(I think disabling the floating point registers was just a red herring;
I'll confirm that next)
And I can now call this fib code happily via the FFI:
fibs :: [Int]
fibs = 1:1:zipWith (+) fibs (tail fibs)
foreign export ccall fib :: Int -> Int
fib :: Int -> Int
fib = (fibs !!)
For posterity, more detail on the crashing case earlier (this is fixed now
with proper storage and updating of the frame pointer):
Calling fib(1) or fib(2) worked, but calling fib(3) triggered the crash.
This was the backtrace, where you can see the errant 0x0000000100f05110
frame values.
(lldb) bt
* thread #1: tid = 0xac6ed, 0x0000000100f05110, queue =
'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=2,
address=0x100f05110)
frame #0: 0x0000000100f05110
frame #1: 0x0000000100f05110
* frame #2: 0x00000001000ffc9c HelloHaskell`-[SPJViewController
viewDidLoad](self=0x0000000144e0cf10, _cmd=0x0000000186ae429a) + 76 at
SPJViewController.m:22
frame #3: 0x00000001862f8b70 UIKit`-[UIViewController
loadViewIfRequired] + 692
frame #4: 0x00000001862f8880 UIKit`-[UIViewController view] + 32
frame #5: 0x00000001862feeb0 UIKit`-[UIWindow
addRootViewControllerViewIfPossible] + 72
frame #6: 0x00000001862fc6d4 UIKit`-[UIWindow _setHidden:forced:] + 296
frame #7: 0x000000018636d2bc UIKit`-[UIWindow makeKeyAndVisible] + 56
frame #8: 0x000000018657ff74 UIKit`-[UIApplication
_callInitializationDelegatesForMainScene:transitionContext:] + 2804
frame #9: 0x00000001865824ec UIKit`-[UIApplication
_runWithMainScene:transitionContext:completion:] + 1480
frame #10: 0x0000000186580b84 UIKit`-[UIApplication
workspaceDidEndTransaction:] + 184
frame #11: 0x0000000189d846ac FrontBoardServices`__31-[FBSSerialQueue
performAsync:]_block_invoke + 28
frame #12: 0x0000000181c7a360
CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 20
frame #13: 0x0000000181c79468 CoreFoundation`__CFRunLoopDoBlocks + 312
frame #14: 0x0000000181c77a8c CoreFoundation`__CFRunLoopRun + 1756
frame #15: 0x0000000181ba5664 CoreFoundation`CFRunLoopRunSpecific + 396
frame #16: 0x0000000186363140 UIKit`-[UIApplication _run] + 552
frame #17: 0x000000018635e164 UIKit`UIApplicationMain + 1488
frame #18: 0x0000000100100268 HelloHaskell`main(argc=1,
argv=0x000000016fd07a58) + 204 at main.m:24
frame #19: 0x00000001921eea08 libdyld.dylib`start + 4
On Tue, Aug 12, 2014 at 11:24 AM, Karel Gardas
On 08/12/14 11:03 AM, Luke Iannini wrote:
It looks like it's jumping somewhere strange; lldb tells me it's to 0x100e05110: .long 0x00000000 ; unknown opcode 0x100e05114: .long 0x00000000 ; unknown opcode 0x100e05118: .long 0x00000000 ; unknown opcode 0x100e0511c: .long 0x00000000 ; unknown opcode 0x100e05120: .long 0x00000000 ; unknown opcode 0x100e05124: .long 0x00000000 ; unknown opcode 0x100e05128: .long 0x00000000 ; unknown opcode 0x100e0512c: .long 0x00000000 ; unknown opcode
If I put a breakpoint on StgRun and step by instruction, I seem to make it to about: https://github.com/lukexi/ghc/blob/e99b7a41e64f3ddb9bb420c0d5583f 0e302e321e/rts/StgCRun.c#L770 (give or take a line)
strange that it's in the middle of the stp isns block. Anyway, this looks like a cpu exception doesn't it? You will need to find out the reg which holds the "exception reason" value and then look on it in your debugger to find out what's going wrong there.
Karel