For future listener frames async unwinding produces frames with
`pc_offset` set to 0, because this frames correspond to closures
which will be invoked once the future completes. Such frames
are different from most other frames which correspond to real
call or yield locations within native code and have non-zero
`pc_offset`.
Because there is no call-/yield- site at 0 compiler does not emit
any source location information into CodeSourceMap and consequently
runtime can't produce much beyond file name in the stack trace for
these special frames.
To make matters worse ordering of code objects in the AOT snapshot
could affect symbolization of such frames - sometimes resulting in
an arbitrary token position being attached to the symbolized frame.
This CL adds more special handling of these frames into
StackTrace::ToCString and changes compiler to emit a dummy source
position descriptor for the start of every closure function.
This descriptor is encoded as
ChangePosition function.token_pos()
AdvancePC 0
in the CodeSourceMap. This entry is then handled specially when
generating DWARF.
TEST=vm/dart{,_2}/causal_stacks/async_throws_stack_lazy{,_lazy_non_symbolic}_test
Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-linux-product-x64-try,vm-kernel-precomp-linux-debug-x64-try,vm-kernel-precomp-dwarf-linux-product-x64-try
Change-Id: I80740dd2c3cb03d6c03c35e1b3bde2cacbe033e0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/219781
Commit-Queue: Slava Egorov <vegorov@google.com>
Reviewed-by: Tess Strickland <sstrickl@google.com>
Reviewed-by: Clement Skau <cskau@google.com>
Vyacheslav Egorov
64d30f848b