From a4eb23205a7723917fc26e778dd2ab65d8aa9e84 Mon Sep 17 00:00:00 2001
From: Helmut Eller <eller.helmut@gmail.com>
Date: Tue, 24 Mar 2026 09:37:09 +0100
Subject: [PATCH] Fix igc_header for Mingw64

* src/igc-types.h (union igc_header): Use uint32_t instead for size_t.
Apparently needed for Mingw64; with size_t the header grows to 16 bytes.
* src/igc.c: Move static assert to igc-types.h.
---
 src/igc-types.h | 11 +++++++----
 src/igc.c       |  2 --
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/igc-types.h b/src/igc-types.h
index 681322388ed..f5327c38783 100644
--- a/src/igc-types.h
+++ b/src/igc-types.h
@@ -96,15 +96,15 @@ union igc_header
   {
     enum igc_tag tag : IGC_HEADER_TAG_BITS;
     enum igc_obj_type obj_type : IGC_HEADER_TYPE_BITS;
-    size_t hash : IGC_HEADER_HASH_BITS;
-    size_t nwords : IGC_HEADER_NWORDS_BITS;
+    uint32_t hash : IGC_HEADER_HASH_BITS;
+    uint32_t nwords : IGC_HEADER_NWORDS_BITS;
   } s;
 #endif
 #ifdef WORDS_BIGENDIAN
   struct
   {
-    size_t nwords : IGC_HEADER_NWORDS_BITS;
-    size_t hash : IGC_HEADER_HASH_BITS;
+    uint32_t nwords : IGC_HEADER_NWORDS_BITS;
+    uint32_t hash : IGC_HEADER_HASH_BITS;
     enum igc_obj_type obj_type : IGC_HEADER_TYPE_BITS;
     enum igc_tag tag : IGC_HEADER_TAG_BITS;
   } s;
@@ -113,4 +113,7 @@ union igc_header
   GCALIGNED_UNION_MEMBER
 };
 
+static_assert (sizeof (*(union igc_header*) 0).s == 8);
+static_assert (sizeof (union igc_header) == 8);
+
 #endif /* EMACS_IGC_TYPES_H */
diff --git a/src/igc.c b/src/igc.c
index a10209da70f..a0c7c3bb37f 100644
--- a/src/igc.c
+++ b/src/igc.c
@@ -663,8 +663,6 @@ struct igc_fwd
   mps_addr_t new_addr;
 };
 
-static_assert (sizeof (union igc_header) == 8);
-
 static void
 check_header_bit (union igc_header h1, size_t i, size_t shift)
 {