fixed undoing bitfields on Windows

* It turns out that `bool` (_Bool) in bitfields may cause
  padding to the next 32-bit word.
  This was only observed on MinGW.
  I am not entirely sure why, although the C standard does
  not guarantee much with regard to bitfield memory layout
  and there are 64-bit available due to passing anyway.
  Actually, they could also be layed out in a different order.
* I am now consistently using guint instead of `bool` in bitfields
  to prevent any potential surprises.
* The way that guint was aliased with bitfield structs
  for undoing teco_machine_main_t and teco_machine_qregspec_t flags
  was therefore insecure.
  It was not guaranteed that the __flags field really "captures"
  all of the bit field.
  Even with `guint v : 1` fields, this was not guaranteed.
  We would have required a static assertion for robustness.
  Alternatively, we could have declared a `gsize __flags` variable
  as well. This __should__ be safe since gsize should always be
  pointer sized and correspond to the platform's alignment.
  However, it's also not 100% guaranteed.
  Using classic ANSI C enums with bit operations to encode multiple
  fields and flags into a single integer also doesn't look very
  attractive.
* Instead, we now define scalar types with their own teco_undo_push()
  shortcuts for the bitfield structs.
  This is in one way simpler and much more robust, but on the other
  hand complicates access to the flag variables.
* It's a good question whether a `struct __attribute__((packed))` bitfield
  with guint fields would be a reliable replacement for flag enums, that
  are communicated with the "outside" (TECO) world.
  I am not going to risk it until GCC gives any guarantees, though.
  For the time being, bitfields are only used internally where
  the concrete memory layout (bit positions) is not crucial.
* This fixes the test suite and therefore probably CI and nightly
  builds on Windows.
* Test case: Rub out `@I//` or `@Xq` until before the `@`.
  The parser doesn't know that `@` is still set and allows
  all sorts of commands where `@` should be forbidden.
* It's unknown how long this has been broken on Windows - quite
  possibly since v2.0.

1 files changed, 6 insertions, 0 deletions

diff --git a/tests/testsuite.at b/tests/testsuite.at
index 3a33838..b0ca8c0 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -357,6 +357,12 @@ AT_CHECK([$SCITECO_CMDLINE "GaGb{-4D}"], 0, ignore, stderr)
 AT_FAIL_IF([$GREP "^Error:" stderr])
 AT_CLEANUP
 
+AT_SETUP([Restore flags after rub out])
+# Must throw an error if the @ flag is restored properly.
+AT_CHECK([$SCITECO_CMDLINE '0@W{-D}C'], 0, ignore, stderr)
+AT_FAIL_IF([! $GREP "^Error:" stderr])
+AT_CLEANUP
+
 AT_SETUP([Searches from macro calls])
 AT_CHECK([$SCITECO_CMDLINE "@^Um{:@S/XXX/} :Mm\"S(0/0)' Mm\"S(0/0)'"], 0, ignore, stderr)
 AT_FAIL_IF([$GREP "^Error:" stderr])