Fix Py_BUILD_ASSERT on non-constant expression

Author: namniav

Include/cpython/pyatomic_msc.h

@@ -16,7 +16,7 @@
 #include <intrin.h>
 
 #define _Py_atomic_ASSERT_ARG_TYPE(TYPE) \
-    Py_BUILD_ASSERT(sizeof(*obj) == sizeof(TYPE))
+    static_assert(sizeof(*obj) == sizeof(TYPE), "")
 
 
 // --- _Py_atomic_add --------------------------------------------------------

Include/internal/pycore_bitutils.h

@@ -36,7 +36,7 @@ _Py_bswap16(uint16_t word)
 #if defined(_PY_HAVE_BUILTIN_BSWAP) || _Py__has_builtin(__builtin_bswap16)
     return __builtin_bswap16(word);
 #elif defined(_MSC_VER)
-    Py_BUILD_ASSERT(sizeof(word) == sizeof(unsigned short));
+    static_assert(sizeof(word) == sizeof(unsigned short), "");
     return _byteswap_ushort(word);
 #else
     // Portable implementation which doesn't rely on circular bit shift
@@ -51,7 +51,7 @@ _Py_bswap32(uint32_t word)
 #if defined(_PY_HAVE_BUILTIN_BSWAP) || _Py__has_builtin(__builtin_bswap32)
     return __builtin_bswap32(word);
 #elif defined(_MSC_VER)
-    Py_BUILD_ASSERT(sizeof(word) == sizeof(unsigned long));
+    static_assert(sizeof(word) == sizeof(unsigned long), "");
     return _byteswap_ulong(word);
 #else
     // Portable implementation which doesn't rely on circular bit shift
@@ -97,12 +97,12 @@ _Py_popcount32(uint32_t x)
 #if (defined(__clang__) || defined(__GNUC__))
 
 #if SIZEOF_INT >= 4
-    Py_BUILD_ASSERT(sizeof(x) <= sizeof(unsigned int));
+    static_assert(sizeof(x) <= sizeof(unsigned int), "");
     return __builtin_popcount(x);
 #else
     // The C standard guarantees that unsigned long will always be big enough
     // to hold a uint32_t value without losing information.
-    Py_BUILD_ASSERT(sizeof(x) <= sizeof(unsigned long));
+    static_assert(sizeof(x) <= sizeof(unsigned long), "");
     return __builtin_popcountl(x);
 #endif
 
@@ -156,7 +156,7 @@ _Py_bit_length(unsigned long x)
     }
 #elif defined(_MSC_VER)
     // _BitScanReverse() is documented to search 32 bits.
-    Py_BUILD_ASSERT(sizeof(unsigned long) <= 4);
+    static_assert(sizeof(unsigned long) <= 4, "");
     unsigned long msb;
     if (_BitScanReverse(&msb, x)) {
         return (int)msb + 1;

Include/internal/pycore_pyhash.h

@@ -10,13 +10,13 @@ static inline Py_hash_t
 _Py_HashPointerRaw(const void *ptr)
 {
     uintptr_t x = (uintptr_t)ptr;
-    Py_BUILD_ASSERT(sizeof(x) == sizeof(ptr));
+    static_assert(sizeof(x) == sizeof(ptr), "");
 
     // Bottom 3 or 4 bits are likely to be 0; rotate x by 4 to the right
     // to avoid excessive hash collisions for dicts and sets.
     x = (x >> 4) | (x << (8 * sizeof(uintptr_t) - 4));
 
-    Py_BUILD_ASSERT(sizeof(x) == sizeof(Py_hash_t));
+    static_assert(sizeof(x) == sizeof(Py_hash_t), "");
     return (Py_hash_t)x;
 }
 

Include/pymacro.h

@@ -40,6 +40,13 @@
    by "__LINE__". */
 #define Py_STRINGIFY(x) _Py_XSTRINGIFY(x)
 
+#define _Py_CONCAT(x, y) x##y
+
+/* Concatenate the arguments. An indirection is required for expanding
+   arguments once. For example Py_CONCAT(name, __LINE__) is replaced by name
+   followed by the line number, not by "__LINE__". */
+#define Py_CONCAT(x, y) _Py_CONCAT(x, y)
+
 /* Get the size of a structure member in bytes */
 #define Py_MEMBER_SIZE(type, member) sizeof(((type *)0)->member)
 
@@ -56,13 +63,44 @@
    #define foo_to_char(foo)  \
        ((char *)(foo)        \
         + Py_BUILD_ASSERT_EXPR(offsetof(struct foo, string) == 0))
+   Originaly written by Rusty Russell, public domain, http://ccodearchive.net/
+   Modified to prohibit variable-length arrays(VLA). */
+#if defined(__cplusplus)
+    template<typename T>
+    struct _Py_BUILD_ASSERT_EXPR_prohibit_vla {
+        static_assert(sizeof(T) == 1,
+            "Py_BUILD_ASSERT_EXPR can only be used with constant "
+            "expression of value true");
+    };
+#  define Py_BUILD_ASSERT_EXPR(cond) \
+        (!sizeof(_Py_BUILD_ASSERT_EXPR_prohibit_vla<char[1 - 2 * !(cond)]>))
+#elif defined(_MSC_VER)
+#  define Py_BUILD_ASSERT_EXPR(cond) \
+        (!sizeof( \
+            __pragma(warning(push)) \
+            __pragma(warning(suppress: 4116)) \
+            enum { \
+                Py_CONCAT(_Py_BUILD_ASSERT_EXPR_prohibit_vla_,__LINE__) = \
+                    sizeof(char[1 - 2 * !(cond)]) \
+            } \
+            __pragma(warning(pop)) \
+        ))
+#else
+#  define Py_BUILD_ASSERT_EXPR(cond) \
+        (!sizeof( \
+            enum { \
+                Py_CONCAT(_Py_BUILD_ASSERT_EXPR_prohibit_vla_,__LINE__) = \
+                    sizeof(char[1 - 2 * !(cond)]) \
+            } \
+        ))
+#endif
 
-   Written by Rusty Russell, public domain, http://ccodearchive.net/ */
-#define Py_BUILD_ASSERT_EXPR(cond) \
-    (sizeof(char [1 - 2*!(cond)]) - 1)
-
-#define Py_BUILD_ASSERT(cond)  do {         \
-        (void)Py_BUILD_ASSERT_EXPR(cond);   \
+/* Deprecated, use static_assert instead. */
+#define Py_BUILD_ASSERT(cond)  do { \
+        Py_DEPRECATED(3.13) \
+        int _Py_BUILD_ASSERT_is_deprecated_use_static_assert_instead = 0; \
+        _Py_BUILD_ASSERT_is_deprecated_use_static_assert_instead; \
+        static_assert(cond, ""); \
     } while(0)
 
 /* Get the number of elements in a visible array

Misc/NEWS.d/next/C API/2024-04-20-14-05-12.gh-issue-118124.K-TPl4.rst

@@ -0,0 +1,3 @@
+Deprecates :c:macro:`Py_BUILD_ASSERT`. Passing non-constant expression to
+:c:macro:`Py_BUILD_ASSERT` or :c:macro:`Py_BUILD_ASSERT_EXPR` now makes
+compilation failed.

Modules/_ctypes/_ctypes.c

@@ -2750,7 +2750,7 @@ unique_key(CDataObject *target, Py_ssize_t index)
     char *cp = string;
     size_t bytes_left;
 
-    Py_BUILD_ASSERT(sizeof(string) - 1 > sizeof(Py_ssize_t) * 2);
+    static_assert(sizeof(string) - 1 > sizeof(Py_ssize_t) * 2, "");
     cp += sprintf(cp, "%x", Py_SAFE_DOWNCAST(index, Py_ssize_t, int));
     while (target->b_base) {
         bytes_left = sizeof(string) - (cp - string) - 1;

Modules/_ssl.c

@@ -3620,7 +3620,7 @@ static PyObject *
 get_options(PySSLContext *self, void *c)
 {
     uint64_t options = SSL_CTX_get_options(self->ctx);
-    Py_BUILD_ASSERT(sizeof(unsigned long long) >= sizeof(options));
+    static_assert(sizeof(unsigned long long) >= sizeof(options), "");
     return PyLong_FromUnsignedLongLong(options);
 }
 
@@ -3642,7 +3642,7 @@ set_options(PySSLContext *self, PyObject *arg, void *c)
     if (new_opts_arg == (unsigned long long)-1 && PyErr_Occurred()) {
         return -1;
     }
-    Py_BUILD_ASSERT(sizeof(new_opts) >= sizeof(new_opts_arg));
+    static_assert(sizeof(new_opts) >= sizeof(new_opts_arg), "");
     new_opts = (uint64_t)new_opts_arg;
 
     opts = SSL_CTX_get_options(self->ctx);
@@ -6062,7 +6062,7 @@ sslmodule_init_socketapi(PyObject *module)
 static int
 sslmodule_add_option(PyObject *m, const char *name, uint64_t value)
 {
-    Py_BUILD_ASSERT(sizeof(unsigned long long) >= sizeof(value));
+    static_assert(sizeof(unsigned long long) >= sizeof(value), "");
     return PyModule_Add(m, name, PyLong_FromUnsignedLongLong(value));
 }
 

Modules/_testcapi/hash.c

@@ -54,7 +54,7 @@ hash_pointer(PyObject *Py_UNUSED(module), PyObject *arg)
     }
 
     Py_hash_t hash = Py_HashPointer(ptr);
-    Py_BUILD_ASSERT(sizeof(long long) >= sizeof(hash));
+    static_assert(sizeof(long long) >= sizeof(hash), "");
     return PyLong_FromLongLong(hash);
 }
 
@@ -64,7 +64,7 @@ object_generichash(PyObject *Py_UNUSED(module), PyObject *arg)
 {
     NULLABLE(arg);
     Py_hash_t hash = PyObject_GenericHash(arg);
-    Py_BUILD_ASSERT(sizeof(long long) >= sizeof(hash));
+    static_assert(sizeof(long long) >= sizeof(hash), "");
     return PyLong_FromLongLong(hash);
 }
 

Modules/_testcapi/time.c

@@ -15,7 +15,7 @@ pytime_from_nanoseconds(PyTime_t *tp, PyObject *obj)
         return -1;
     }
 
-    Py_BUILD_ASSERT(sizeof(long long) == sizeof(PyTime_t));
+    static_assert(sizeof(long long) == sizeof(PyTime_t), "");
     *tp = (PyTime_t)nsec;
     return 0;
 }
@@ -98,7 +98,7 @@ _PyTestCapi_Init_Time(PyObject *m)
     if (PyModule_AddFunctions(m, test_methods) < 0) {
         return -1;
     }
-    Py_BUILD_ASSERT(sizeof(long long) == sizeof(PyTime_t));
+    static_assert(sizeof(long long) == sizeof(PyTime_t), "");
     if (PyModule_AddObject(m, "PyTime_MIN", PyLong_FromLongLong(PyTime_MIN)) < 0) {
         return 1;
     }

Modules/_testcapimodule.c

@@ -2905,8 +2905,22 @@ test_macros(PyObject *self, PyObject *Py_UNUSED(args))
 
     // static_assert(), Py_BUILD_ASSERT()
     static_assert(1 == 1, "bug");
+    // Py_BUILD_ASSERT is now deprecated
+#if defined(__GNUC__) || defined(__clang__)
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+#  pragma GCC diagnostic ignored "-Wunused-value"
+#elif defined(_MSC_VER)
+#  pragma warning(push)
+#  pragma warning(disable:4996)
+#  pragma warning(disable:4555)
+#endif
     Py_BUILD_ASSERT(1 == 1);
-
+#if defined(__GNUC__)
+#  pragma GCC diagnostic pop
+#elif defined(_MSC_VER)
+#  pragma warning(pop)
+#endif
 
     // Py_MIN(), Py_MAX(), Py_ABS()
     assert(Py_MIN(5, 11) == 5);