From 2d94529192c75236f8b3c959d1aa082b0dc9e0ce Mon Sep 17 00:00:00 2001
From: Yann Collet <yann.collet.73@gmail.com>
Date: Wed, 18 Jun 2025 16:25:35 -0700
Subject: [PATCH] added test_alias

expected to fail due to #1013
---
 .github/workflows/ci.yml | 11 ++++++-----
 .gitignore               |  1 +
 tests/Makefile           |  6 +++++-
 tests/test_alias.c       | 18 ++++++++++++++++++
 4 files changed, 30 insertions(+), 6 deletions(-)
 create mode 100644 tests/test_alias.c

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 82dfff1..be746ca 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -37,15 +37,11 @@
 #   elapsed time.
 #
 # Todos:
-# - [ ] Linux: Add native ARM runner.
 # - [ ] Linux: Add native ARM64 runner.
 # - [ ] Linux: Add native PPC64LE runner.
 # - [ ] Linux: Add native S390X runner.
-# - [ ] Windows: Add VS2013.
-# - [ ] Windows: Add VS2015.
 # - [ ] Windows: Add clang for msys2.
-# - [ ] Windows: Add native or emulated ARM runner.
-# - [ ] Windows: Add native or emulated ARM64 runner.
+# - [ ] Windows: Add native or emulated ARM64 runner (note: currently unreliable)
 
 
 # Name of the workflow is also displayed as a SVG badge
@@ -167,6 +163,11 @@ jobs:
       run: |
         make clean test-all
 
+    - name: test-alias
+      run: |
+        make clean
+        make -C tests test_alias
+
 
   ubuntu-consistency:
     name: Linux x64 check results consistency
diff --git a/.gitignore b/.gitignore
index 764a311..d0661ef 100644
--- a/.gitignore
+++ b/.gitignore
@@ -21,6 +21,7 @@ dispatch
 tests/generate_unicode_test
 tests/sanity_test
 tests/sanity_test_vectors_generator
+tests/test_alias
 fuzzer
 
 # Mac OS-X artefacts
diff --git a/tests/Makefile b/tests/Makefile
index d91a990..f1f60ae 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -50,7 +50,7 @@ C_SRCDIRS = . .. ../cli
 include ../build/make/multiconf.make
 
 .PHONY: all
-all: test
+all: test test_alias
 
 .PHONY: test
 test: test_multiInclude test_unicode test_sanity
@@ -127,6 +127,10 @@ sanity_test_vectors.h: sanity_test_vectors_generator
 multiInclude_withxxhash:
 $(eval $(call c_program,multiInclude_withxxhash,multiInclude.o xxhash.o))
 
+test_alias: CPPFLAGS += -I..
+test_alias: CFLAGS += -O3 -Werror
+$(eval $(call c_program,test_alias,test_alias.o))
+
 .PHONY: clean
 clean:
 	@$(RM) *.o
diff --git a/tests/test_alias.c b/tests/test_alias.c
new file mode 100644
index 0000000..af1065f
--- /dev/null
+++ b/tests/test_alias.c
@@ -0,0 +1,18 @@
+#define XXH_INLINE_ALL
+
+#include <inttypes.h>
+#include <stdio.h>
+#include "xxhash.h"
+
+int main() {
+	// it seems this has to be exactly 24 bytes.
+	union {
+		char x[24];
+		// force 8-byte alignment without making
+		// aliasable with uint64_t.
+		void *y[3];
+	} data = {.x = "garblegarblegarblegarble"};
+	uint64_t hash = XXH64(&data, sizeof(data), 0);
+	printf("%016"PRIx64"\n", hash);
+	return 0;
+}