[PATCH] Fixed bytevector size checks in macros write-c-struct and read-c-struct

 From 2f6bf52bfe71ee10a65489ea94abdaf1a90d7c8d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tommi=20H=C3=B6yn=C3=A4l=C3=A4nmaa?=
  <[email protected]>
Date: Sat, 29 Nov 2025 11:21:23 +0200
Subject: [PATCH] Fixed bytevector size checks in macros write-c-struct and
  read-c-struct.

The current bytevector size checks in macros write-c-struct and 
read-c-struct trigger an error if the argument bytevector is larger than 
needed. The correct way is to trigger an error if the bytevector is too 
small.

---
  module/system/foreign.scm | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/module/system/foreign.scm b/module/system/foreign.scm
index a75c37da1..4a505bdd2 100644
--- a/module/system/foreign.scm
+++ b/module/system/foreign.scm
@@ -184,7 +184,7 @@ not cross-compiling; otherwise leave it to be 
evaluated at run-time."
    (let ((bv %bv)
          (offset %offset)
          (size (compile-time-eval (sizeof (list type ...)))))
-    (unless (<= (bytevector-length bv) (+ offset size))
+    (unless (>= (bytevector-length bv) (+ offset size))
        (error "destination bytevector too small"))
      (let*-values (((field offset)
                     (read-field bv offset (compile-time-eval type)))
@@ -229,7 +229,7 @@ not cross-compiling; otherwise leave it to be 
evaluated at run-time."
    (let ((bv %bv)
          (offset %offset)
          (size (compile-time-eval (sizeof (list type ...)))))
-    (unless (<= (bytevector-length bv) (+ offset size))
+    (unless (>= (bytevector-length bv) (+ offset size))
        (error "destination bytevector too small"))
      (let* ((offset (write-field bv offset (compile-time-eval type) field))
             ...)
-- 
2.47.3


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