From 763c8d3a428994f7474a8234497936aed0438e6b Mon Sep 17 00:00:00 2001
From: bymehul <noreply.mehul@proton.me>
Date: Wed, 11 Mar 2026 03:04:26 +0530
Subject: [PATCH] Fix generic cycle deadlock in struct layout

---
 src/types.cpp                     |  5 +++--
 tests/issues/run.bat              |  1 +
 tests/issues/run.sh               |  6 ++++++
 tests/issues/test_issue_6401.odin | 16 ++++++++++++++++
 4 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 tests/issues/test_issue_6401.odin

diff --git a/src/types.cpp b/src/types.cpp
index 0ecce1adc..b11e95452 100644
--- a/src/types.cpp
+++ b/src/types.cpp
@@ -4201,8 +4201,9 @@ gb_internal i64 type_align_of_internal(Type *t, TypePath *path) {
 		if (t->Struct.is_packed) {
 			return 1;
 		}
-
-		type_set_offsets(t);
+		// Avoid forcing offset computation here. The caller's type-path state must
+		// be able to detect recursive field cycles before any nested struct tries to
+		// re-enter this struct's offset mutex.
 
 		i64 max = 1;
 		for_array(i, t->Struct.fields) {
diff --git a/tests/issues/run.bat b/tests/issues/run.bat
index 9e722886d..3db9d48c2 100644
--- a/tests/issues/run.bat
+++ b/tests/issues/run.bat
@@ -31,6 +31,7 @@ set COMMON=-define:ODIN_TEST_FANCY=false -file -vet -strict-style -ignore-unused
 ..\..\..\odin test ..\test_issue_6101.odin %COMMON%  || exit /b
 ..\..\..\odin test ..\test_issue_6165.odin %COMMON%  || exit /b
 ..\..\..\odin build ..\test_issue_6240.odin %COMMON% 2>&1 | find /c "Error:" | findstr /x "3" || exit /b
+..\..\..\odin build ..\test_issue_6401.odin %COMMON% 2>&1 | find /c "Error:" | findstr /x "3" || exit /b
 
 @echo off
 
diff --git a/tests/issues/run.sh b/tests/issues/run.sh
index e2e45dbfa..01e6a6a28 100755
--- a/tests/issues/run.sh
+++ b/tests/issues/run.sh
@@ -43,6 +43,12 @@ else
 	echo "SUCCESSFUL 0/1"
 	exit 1
 fi
+if [[ $($ODIN build ../test_issue_6401.odin $COMMON 2>&1 >/dev/null | grep -c "Error:") -eq 3 ]] ; then
+	echo "SUCCESSFUL 1/1"
+else
+	echo "SUCCESSFUL 0/1"
+	exit 1
+fi
 set +x
 
 popd
diff --git a/tests/issues/test_issue_6401.odin b/tests/issues/test_issue_6401.odin
new file mode 100644
index 000000000..0f7cd58b6
--- /dev/null
+++ b/tests/issues/test_issue_6401.odin
@@ -0,0 +1,16 @@
+// Tests issue #6401 https://github.com/odin-lang/Odin/issues/6401
+package test_issues
+
+Wrapper :: struct(T: typeid) {
+	value: T,
+}
+
+A :: struct {
+	value: Wrapper(B),
+}
+
+B :: struct {
+	value: A,
+}
+
+main :: proc() {}