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displaced_step_inferior_state::reset and displaced_step_clear appear to
have the same goal, but they don't do the same thing.
displaced_step_inferior_state::reset clears more things than
displaced_step_clear, but it misses free'ing the closure, which
displaced_step_clear does.
This patch replaces displaced_step_clear's implementation with just a call to
displaced_step_inferior_state::reset. It then changes
displaced_step_inferior_state::step_closure to be a unique_ptr, to indicate the
fact that displaced_step_inferior_state owns the closure (and so that it is
automatically freed when the field is reset).
The test gdb.base/step-over-syscall.exp caught a problem when doing this, which
I consider to be a latent bug which my cleanup exposes. In
handle_inferior_event, in the TARGET_WAITKIND_FORKED case, if we displaced-step
over a fork syscall, we make sure to restore the memory that we used as a
displaced-stepping buffer in the child. We do so using the
displaced_step_inferior_state of the parent. However, we do it after calling
displaced_step_fixup for the parent, which clears the information in the
parent's displaced_step_inferior_state. It worked fine before, because
displaced_step_clear didn't completely clear the displaced_step_inferior_state
structure, so the required information (in this case the gdbarch) was
still available after clearing.
I fixed it by making GDB restore the child's memory before calling the
displaced_step_fixup on the parent. This way, the data in the
displaced_step_inferior_state structure is still valid when we use it for the
child. This is the error you would get in
gdb.base/step-over-syscall.exp without this fix:
/home/smarchi/src/binutils-gdb/gdb/gdbarch.c:3911: internal-error: ULONGEST gdbarch_max_insn_length(gdbarch*): Assertion `gdbarch != NULL' failed.
gdb/ChangeLog:
* infrun.c (get_displaced_step_closure_by_addr): Adjust to
std::unique_ptr.
(displaced_step_clear): Rename to...
(displaced_step_reset): ... this. Just call displaced->reset ().
(displaced_step_clear_cleanup): Rename to...
(displaced_step_reset_cleanup): ... this.
(displaced_step_prepare_throw): Adjust to std::unique_ptr.
(displaced_step_fixup): Likewise.
(resume_1): Likewise.
(handle_inferior_event): Restore child's memory before calling
displaced_step_fixup on the parent.
* infrun.h (displaced_step_inferior_state) <reset>: Adjust
to std::unique_ptr.
<step_closure>: Change type to std::unique_ptr.
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