Squashed 'external/toxcore/c-toxcore/' content from commit 67badf69

git-subtree-dir: external/toxcore/c-toxcore
git-subtree-split: 67badf69416a74e74f6d7eb51dd96f37282b8455

toxcore/ccompat.h

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+/* SPDX-License-Identifier: GPL-3.0-or-later
+ * Copyright © 2016-2021 The TokTok team.
+ */
+
+/**
+ * C language compatibility macros for varying compiler support.
+ */
+#ifndef C_TOXCORE_TOXCORE_CCOMPAT_H
+#define C_TOXCORE_TOXCORE_CCOMPAT_H
+
+#include <stddef.h>  // NULL, size_t
+
+#include "attributes.h"
+
+//!TOKSTYLE-
+
+// Variable length arrays.
+// VLA(type, name, size) allocates a variable length array with automatic
+// storage duration. VLA_SIZE(name) evaluates to the runtime size of that array
+// in bytes.
+//
+// If C99 VLAs are not available, an emulation using alloca (stack allocation
+// "function") is used. Note the semantic difference: alloca'd memory does not
+// get freed at the end of the declaration's scope. Do not use VLA() in loops or
+// you may run out of stack space.
+#if !defined(DISABLE_VLA) && !defined(_MSC_VER) && defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
+// C99 VLAs.
+#define ALLOC_VLA(type, name, size) type name[size]
+#define SIZEOF_VLA sizeof
+#else
+
+// Emulation using alloca.
+#ifdef _WIN32
+#include <malloc.h>
+#elif defined(__COMPCERT__)
+// TODO(iphydf): This leaks memory like crazy, so compcert is useless for now.
+// Once we're rid of VLAs, we can remove this and compcert becomes useful.
+#define alloca malloc
+#include <stdlib.h>
+#elif defined(__linux__)
+#include <alloca.h>
+#else
+#include <stdlib.h>
+#if !defined(alloca) && defined(__GNUC__)
+#define alloca __builtin_alloca
+#endif
+#endif
+
+#define ALLOC_VLA(type, name, size)                       \
+    const size_t name##_vla_size = (size) * sizeof(type); \
+    type *const name = (type *)alloca(name##_vla_size)
+#define SIZEOF_VLA(name) name##_vla_size
+
+#endif
+
+#ifdef MAX_VLA_SIZE
+#include <assert.h>
+#define VLA(type, name, size)    \
+    ALLOC_VLA(type, name, size); \
+    assert((size_t)(size) * sizeof(type) <= MAX_VLA_SIZE)
+#else
+#define VLA ALLOC_VLA
+#endif
+
+#if !defined(__cplusplus) || __cplusplus < 201103L
+#define nullptr NULL
+#ifndef static_assert
+#ifdef __GNUC__
+// We'll just assume gcc and clang support C11 _Static_assert.
+#define static_assert _Static_assert
+#else // !__GNUC__
+#define STATIC_ASSERT_(cond, msg, line) typedef int static_assert_##line[(cond) ? 1 : -1]
+#define STATIC_ASSERT(cond, msg, line) STATIC_ASSERT_(cond, msg, line)
+#define static_assert(cond, msg) STATIC_ASSERT(cond, msg, __LINE__)
+#endif // !__GNUC__
+#endif // !static_assert
+#endif // !__cplusplus
+
+#ifdef __GNUC__
+#define GNU_PRINTF(f, a) __attribute__((__format__(__printf__, f, a)))
+#else
+#define GNU_PRINTF(f, a)
+#endif
+
+//!TOKSTYLE+
+
+#endif // C_TOXCORE_TOXCORE_CCOMPAT_H