From c04c685469e093520fc2413c1d364c325f88e952 Mon Sep 17 00:00:00 2001
From: "Markus F.X.J. Oberhumer" <markus@oberhumer.com>
Date: Wed, 8 May 2024 23:08:33 +0200
Subject: [PATCH] src: restrict upx::atomic_exchange to pointer-size for now

---
 misc/cmake/try_compile/types_abi.cpp |  8 ++++
 src/check/dt_cxxlib.cpp              | 55 ++++++++++------------------
 src/util/cxxlib.h                    |  3 ++
 3 files changed, 30 insertions(+), 36 deletions(-)

diff --git a/misc/cmake/try_compile/types_abi.cpp b/misc/cmake/try_compile/types_abi.cpp
index 51393c5f..c24242d9 100644
--- a/misc/cmake/try_compile/types_abi.cpp
+++ b/misc/cmake/try_compile/types_abi.cpp
@@ -1,14 +1,22 @@
 // Copyright (C) Markus Franz Xaver Johannes Oberhumer
 
 #include <stddef.h>
+#include <stdint.h>
 
 // check ABI - require proper alignment of fundamental types for use in atomics
 static_assert(alignof(char) == sizeof(char), "");
+static_assert(alignof(signed char) == sizeof(signed char), "");
+static_assert(alignof(unsigned char) == sizeof(unsigned char), "");
 static_assert(alignof(short) == sizeof(short), "");
+static_assert(alignof(unsigned short) == sizeof(unsigned short), "");
 static_assert(alignof(int) == sizeof(int), "");
+static_assert(alignof(unsigned int) == sizeof(unsigned int), "");
 static_assert(alignof(long) == sizeof(long), "");
+static_assert(alignof(unsigned long) == sizeof(unsigned long), "");
 static_assert(alignof(ptrdiff_t) == sizeof(ptrdiff_t), "");
 static_assert(alignof(size_t) == sizeof(size_t), "");
+static_assert(alignof(intptr_t) == sizeof(intptr_t), "");
+static_assert(alignof(uintptr_t) == sizeof(uintptr_t), "");
 static_assert(alignof(void *) == sizeof(void *), "");
 
 int main() { return 0; }
diff --git a/src/check/dt_cxxlib.cpp b/src/check/dt_cxxlib.cpp
index d5f0533e..872acf0c 100644
--- a/src/check/dt_cxxlib.cpp
+++ b/src/check/dt_cxxlib.cpp
@@ -252,48 +252,31 @@ struct Z2_X2 : public X2 {
 
 #if WITH_THREADS
 TEST_CASE("upx::ptr_std_atomic_cast") {
-    (void) upx::ptr_std_atomic_cast((upx_int8_t *) nullptr);
-    (void) upx::ptr_std_atomic_cast((upx_int16_t *) nullptr);
-    (void) upx::ptr_std_atomic_cast((upx_int32_t *) nullptr);
-    (void) upx::ptr_std_atomic_cast((int *) nullptr);
-    (void) upx::ptr_std_atomic_cast((long *) nullptr);
-    (void) upx::ptr_std_atomic_cast((ptrdiff_t *) nullptr);
-    (void) upx::ptr_std_atomic_cast((size_t *) nullptr);
-    (void) upx::ptr_std_atomic_cast((void **) nullptr);
+    // pointer-size
+    CHECK_EQ(upx::ptr_std_atomic_cast((void **) nullptr), nullptr);
+    CHECK_EQ(upx::ptr_std_atomic_cast((uintptr_t *) nullptr), nullptr);
+    CHECK_EQ(upx::ptr_std_atomic_cast((upx_uintptr_t *) nullptr), nullptr);
+#if 1
+    // more fundamental types
+    CHECK_EQ(upx::ptr_std_atomic_cast((char *) nullptr), nullptr);
+    CHECK_EQ(upx::ptr_std_atomic_cast((short *) nullptr), nullptr);
+    CHECK_EQ(upx::ptr_std_atomic_cast((int *) nullptr), nullptr);
+    CHECK_EQ(upx::ptr_std_atomic_cast((long *) nullptr), nullptr);
+    CHECK_EQ(upx::ptr_std_atomic_cast((ptrdiff_t *) nullptr), nullptr);
+    CHECK_EQ(upx::ptr_std_atomic_cast((size_t *) nullptr), nullptr);
+    CHECK_EQ(upx::ptr_std_atomic_cast((upx_int8_t *) nullptr), nullptr);
+    CHECK_EQ(upx::ptr_std_atomic_cast((upx_int16_t *) nullptr), nullptr);
+    CHECK_EQ(upx::ptr_std_atomic_cast((upx_int32_t *) nullptr), nullptr);
+#endif
 }
 #endif
 
 TEST_CASE("upx::atomic_exchange") {
-#if defined(__riscv)
-// RISC-V has no support for subword atomic operations and needs libatomic to emulate
-#else
     {
-        upx_int8_t x = -1;
-        upx_int8_t y = upx::atomic_exchange(&x, (upx_int8_t) 2);
+        upx_uintptr_t x = (upx_uintptr_t) 0 - 1;
+        upx_uintptr_t y = upx::atomic_exchange(&x, (upx_uintptr_t) 2);
         CHECK_EQ(x, 2);
-        CHECK_EQ(y, -1);
-        UNUSED(y);
-    }
-    {
-        upx_int16_t x = -1;
-        upx_int16_t y = upx::atomic_exchange(&x, (upx_int16_t) 2);
-        CHECK_EQ(x, 2);
-        CHECK_EQ(y, -1);
-        UNUSED(y);
-    }
-    {
-        upx_int32_t x = -1;
-        upx_int32_t y = upx::atomic_exchange(&x, (upx_int32_t) 2);
-        CHECK_EQ(x, 2);
-        CHECK_EQ(y, -1);
-        UNUSED(y);
-    }
-#endif // __riscv
-    {
-        size_t x = (size_t) 0 - 1;
-        size_t y = upx::atomic_exchange(&x, (size_t) 2);
-        CHECK_EQ(x, 2);
-        CHECK_EQ(y, (size_t) 0 - 1);
+        CHECK_EQ(y, (upx_uintptr_t) 0 - 1);
         UNUSED(y);
     }
     {
diff --git a/src/util/cxxlib.h b/src/util/cxxlib.h
index 0cfdbc5d..42655388 100644
--- a/src/util/cxxlib.h
+++ b/src/util/cxxlib.h
@@ -204,6 +204,9 @@ forceinline std::atomic<T> *ptr_std_atomic_cast(T *ptr) noexcept {
 // atomic_exchange
 template <class T>
 forceinline T atomic_exchange(T *ptr, T new_value) noexcept {
+#if 1
+    static_assert(sizeof(T) == sizeof(void *)); // UPX convention: restrict to pointer-size for now
+#endif
     static_assert(std::is_standard_layout_v<T>);
     static_assert(std::is_trivially_copyable_v<T>);
 #if !(WITH_THREADS)