[wic][PATCH 1/5] ksparser: reject negative sizes in sizetype()

sizetype() splits "<num>[S|s|K|k|M|G]" into an integer count and a unit
suffix, then multiplies. int() happily parses a leading minus, so "-1M"
produced -1024 and "-5" produced -5120 with no complaint. A negative
size is meaningless for every consumer of sizetype() (--size,
--fixed-size, --offset, --extra-*-space, and the empty source plugin's
size=/bs= params); it can only corrupt the resulting image layout.

Reject a negative size with the same ArgumentTypeError the parser already
raises for other malformed sizes.

AI-Generated: codex/claude-opus 4.8 (xhigh)
Signed-off-by: Trevor Woerner <[email protected]>
---
 src/wic/ksparser.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/wic/ksparser.py b/src/wic/ksparser.py
index 8e5fbfadd81f..24c7015b336d 100644
--- a/src/wic/ksparser.py
+++ b/src/wic/ksparser.py
@@ -68,6 +68,8 @@ def sizetype(default, size_in_bytes=False):
             except ValueError:
                 raise ArgumentTypeError("Invalid size: %r" % arg)
 
+        if size < 0:
+            raise ArgumentTypeError("Invalid size: %r" % arg)
 
         if size_in_bytes:
             if suffix == 's' or suffix == 'S':
-- 
2.50.0.173.g8b6f19ccfc3a