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Subject: [Bug c++/106188] New: [11.3 Regression] [coroutines] Incorrect frame
 layout after transforming conditional statement without top-level bind
 expression
Date: Mon, 04 Jul 2022 19:30:58 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106188

            Bug ID: 106188
           Summary: [11.3 Regression] [coroutines] Incorrect frame layout
                    after transforming conditional statement without
                    top-level bind expression
           Product: gcc
           Version: 11.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc-bugzilla at decltype dot org
  Target Milestone: ---

Created attachment 53257
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D53257&action=3Dedit
Minimal test case

During `morph_fn_to_coro`, `await_statement_walker` rewrites IF and SWITCH
statements by breaking the condition out into a local variable. The new
variable is inserted at the beginning of the containing bind expression.

If the original function lacked a top-level bind expression, this pushes the
resume function pointer and all following fixed-layout frame members away f=
rom
their intended placement.

Expected frame layout:
_Coro_resume_fn
_Coro_destroy_fn
_Coro_promise
_Coro_self_handle
params
_Coro_resume_index
_Coro_frame_needs_free
_Coro_initial_await_resume_called
locals (ifcd/swch)

Actual frame layout (since 11.3.0):
locals (ifcd/swch) <- out of place
_Coro_resume_fn
_Coro_destroy_fn
_Coro_promise
_Coro_self_handle
params
_Coro_resume_index
_Coro_frame_needs_free
_Coro_initial_await_resume_called

The attached program triggers this error and crashes. Uncommenting the unus=
ed
local variable resolves the crash.=