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#ifndef RBIMPL_MEMORY_H /*-*-C++-*-vi:se ft=cpp:*/ #define RBIMPL_MEMORY_H /** * @file * @author Ruby developers <ruby-core@ruby-lang.org> * @copyright This file is a part of the programming language Ruby. * Permission is hereby granted, to either redistribute and/or * modify this file, provided that the conditions mentioned in the * file COPYING are met. Consult the file for details. * @warning Symbols prefixed with either `RBIMPL` or `rbimpl` are * implementation details. Don't take them as canon. They could * rapidly appear then vanish. The name (path) of this header file * is also an implementation detail. Do not expect it to persist * at the place it is now. Developers are free to move it anywhere * anytime at will. * @note To ruby-core: remember that this header can be possibly * recursively included from extension libraries written in C++. * Do not expect for instance `__VA_ARGS__` is always available. * We assume C99 for ruby itself but we don't assume languages of * extension libraries. They could be written in C++98. * @brief Memory management stuff. */ #include "ruby/internal/config.h" #ifdef STDC_HEADERS # include <stddef.h> #endif #ifdef HAVE_STRING_H # include <string.h> #endif #ifdef HAVE_STDINT_H # include <stdint.h> #endif #ifdef HAVE_ALLOCA_H # include <alloca.h> #endif #if defined(_MSC_VER) && defined(_WIN64) # include <intrin.h> # pragma intrinsic(_umul128) #endif #include "ruby/internal/attr/alloc_size.h" #include "ruby/internal/attr/const.h" #include "ruby/internal/attr/constexpr.h" #include "ruby/internal/attr/noalias.h" #include "ruby/internal/attr/nonnull.h" #include "ruby/internal/attr/noreturn.h" #include "ruby/internal/attr/restrict.h" #include "ruby/internal/attr/returns_nonnull.h" #include "ruby/internal/cast.h" #include "ruby/internal/dllexport.h" #include "ruby/internal/has/builtin.h" #include "ruby/internal/stdalign.h" #include "ruby/internal/stdbool.h" #include "ruby/internal/xmalloc.h" #include "ruby/backward/2/limits.h" #include "ruby/backward/2/long_long.h" #include "ruby/backward/2/assume.h" #include "ruby/defines.h" /** @cond INTERNAL_MACRO */ /* Make alloca work the best possible way. */ #if defined(alloca) # /* Take that. */ #elif RBIMPL_HAS_BUILTIN(__builtin_alloca) # define alloca __builtin_alloca #elif defined(_AIX) # pragma alloca #elif defined(__cplusplus) extern "C" void *alloca(size_t); #else extern void *alloca(); #endif /** @endcond */ #if defined(__DOXYGEN__) /** * @private * * Type that is as twice wider as size_t. This is an implementation detail of * rb_mul_size_overflow(). People should not use it. This is not a good name * either. */ typedef uint128_t DSIZE_T; #elif defined(HAVE_INT128_T) && SIZEOF_SIZE_T <= 8 # define DSIZE_T uint128_t #elif SIZEOF_SIZE_T * 2 <= SIZEOF_LONG_LONG # define DSIZE_T unsigned LONG_LONG #endif /** * @private * * Maximum possible number of bytes that #RB_ALLOCV can allocate using * `alloca`. Anything beyond this is allocated using rb_alloc_tmp_buffer(). * This selection is transparent to users. People don't have to bother. */ #ifdef C_ALLOCA # define RUBY_ALLOCV_LIMIT 0 #else # define RUBY_ALLOCV_LIMIT 1024 #endif /** * Prevents premature destruction of local objects. Ruby's garbage collector * is conservative; it scans the C level machine stack as well. Possible in- * use Ruby objects must remain visible on stack, to be properly marked as * such. However contemporary C compilers do not interface well with this. * Consider the following example: * * ```CXX * auto s = rb_str_new_cstr(" world"); * auto sptr = RSTRING_PTR(s); * auto t = rb_str_new_cstr("hello,"); // Possible GC invocation * auto u = rb_str_cat_cstr(t, sptr); * * RB_GC_GUARD(s); // ensure `s` (and thus `sptr`) do not get GC-ed * ``` * * Here, without the #RB_GC_GUARD, the last use of `s` is _before_ the last use * of `sptr`. Compilers could thus think `s` and `t` are allowed to overlap. * That would eliminate `s` from the stack, while `sptr` is still in use. If * our GC ran at that very moment, `s` gets swept out, which also destroys * `sptr`. Boom! You got a SEGV. * * In order to prevent this scenario #RB_GC_GUARD must be placed _after_ the * last use of `sptr`. Placing #RB_GC_GUARD before dereferencing `sptr` would * be of no use. * * #RB_GC_GUARD would not be necessary at all in the above example if non- * inlined function calls are made on the `s` variable after `sptr` is * dereferenced. Thus, in the above example, calling any un-inlined function * on `s` such as `rb_str_modify(s);` will ensure `s` stays on the stack or * register to prevent a GC invocation from prematurely freeing it. * * Using the #RB_GC_GUARD macro is preferable to using the `volatile` keyword * in C. #RB_GC_GUARD has the following advantages: * * - the intent of the macro use is clear. * * - #RB_GC_GUARD only affects its call site. OTOH `volatile` generates some * extra code every time the variable is used, hurting optimisation. * * - `volatile` implementations may be buggy/inconsistent in some compilers * and architectures. #RB_GC_GUARD is customisable for broken * systems/compilers without negatively affecting other systems. * * - C++ since C++20 deprecates `volatile`. If you write your extension * library in that language there is no escape but to use this macro. * * @param v A variable of ::VALUE type. * @post `v` is still alive. */ #ifdef __GNUC__ #define RB_GC_GUARD(v) \ (*__extension__ ({ \ volatile VALUE *rb_gc_guarded_ptr = &(v); \ __asm__("" : : "m"(rb_gc_guarded_ptr)); \ rb_gc_guarded_ptr; \ })) #elif defined _MSC_VER #define RB_GC_GUARD(v) (*rb_gc_guarded_ptr(&(v))) #else #define HAVE_RB_GC_GUARDED_PTR_VAL 1 #define RB_GC_GUARD(v) (*rb_gc_guarded_ptr_val(&(v),(v))) #endif /* Casts needed because void* is NOT compatible with others in C++. */ /** * Convenient macro that allocates an array of n elements. * * @param type Type of array elements. * @param n Length of the array. * @exception rb_eNoMemError No space left for allocation. * @exception rb_eArgError Integer overflow trying to calculate the length * of continuous memory region of `n` elements of * `type`. * @return Storage instance that is capable of storing at least `n` * elements of type `type`. * @note It doesn't return NULL, even when `n` is zero. * @warning The return value shall be invalidated exactly once by either * ruby_xfree(), ruby_xrealloc(), or ruby_xrealloc2(). It is a * failure to pass it to system free(), because the system and Ruby * might or might not share the same malloc() implementation. */ #define RB_ALLOC_N(type,n) RBIMPL_CAST((type *)ruby_xmalloc2((n), sizeof(type))) /** * Shorthand of #RB_ALLOC_N with `n=1`. * * @param type Type of allocation. * @exception rb_eNoMemError No space left for allocation. * @return Storage instance that can hold an `type` object. * @note It doesn't return NULL. * @warning The return value shall be invalidated exactly once by either * ruby_xfree(), ruby_xrealloc(), or ruby_xrealloc2(). It is a * failure to pass it to system free(), because the system and Ruby * might or might not share the same malloc() implementation. */ #define RB_ALLOC(type) RBIMPL_CAST((type *)ruby_xmalloc(sizeof(type))) /** * Identical to #RB_ALLOC_N() but also nullifies the allocated region before * returning. * * @param type Type of array elements. * @param n Length of the array. * @exception rb_eNoMemError No space left for allocation. * @exception rb_eArgError Integer overflow trying to calculate the length * of continuous memory region of `n` elements of * `type`. * @return Storage instance that is capable of storing at least `n` * elements of type `type`. * @post Returned array is filled with zeros. * @note It doesn't return NULL, even when `n` is zero. * @warning The return value shall be invalidated exactly once by either * ruby_xfree(), ruby_xrealloc(), or ruby_xrealloc2(). It is a * failure to pass it to system free(), because the system and Ruby * might or might not share the same malloc() implementation. */ #define RB_ZALLOC_N(type,n) RBIMPL_CAST((type *)ruby_xcalloc((n), sizeof(type))) /** * Shorthand of #RB_ZALLOC_N with `n=1`. * * @param type Type of allocation. * @exception rb_eNoMemError No space left for allocation. * @return Storage instance that can hold an `type` object. * @post Returned object is filled with zeros. * @note It doesn't return NULL. * @warning The return value shall be invalidated exactly once by either * ruby_xfree(), ruby_xrealloc(), or ruby_xrealloc2(). It is a * failure to pass it to system free(), because the system and Ruby * might or might not share the same malloc() implementation. */ #define RB_ZALLOC(type) (RB_ZALLOC_N(type, 1)) /** * Convenient macro that reallocates an array with a new size. * * @param var A variable of `type`, which points to a storage * instance that was previously returned from * either * - ruby_xmalloc(), * - ruby_xmalloc2(), * - ruby_xcalloc(), * - ruby_xrealloc(), or * - ruby_xrealloc2(). * @param type Type of allocation. * @param n Requested new size of each element. * @exception rb_eNoMemError No space left for allocation. * @exception rb_eArgError Integer overflow trying to calculate the length * of continuous memory region of `n` elements of * `type`. * @return Storage instance that is capable of storing at least `n` * elements of type `type`. * @pre The passed variable must point to a valid live storage instance. * It is a failure to pass a variable that holds an already-freed * pointer. * @note It doesn't return NULL, even when `n` is zero. * @warning Do not assume anything on the alignment of the return value. * There is no guarantee that it inherits the passed argument's * one. * @warning The return value shall be invalidated exactly once by either * ruby_xfree(), ruby_xrealloc(), or ruby_xrealloc2(). It is a * failure to pass it to system free(), because the system and Ruby * might or might not share the same malloc() implementation. */ #define RB_REALLOC_N(var,type,n) \ ((var) = RBIMPL_CAST((type *)ruby_xrealloc2((void *)(var), (n), sizeof(type)))) /** * @deprecated This macro is dangerous (does not bother stack overflow at * all). #RB_ALLOCV is the modern way to do the same thing. * @param type Type of array elements. * @param n Length of the array. * @return A pointer on stack. */ #define ALLOCA_N(type,n) \ RBIMPL_CAST((type *)alloca(rbimpl_size_mul_or_raise(sizeof(type), (n)))) /** * Identical to #RB_ALLOCV_N(), except that it allocates a number of bytes and * returns a void* . * * @param v A variable to hold the just-in-case opaque Ruby object. * @param n Size of allocation, in bytes. * @return A void pointer to `n` bytes storage. * @note `n` may be evaluated twice. */ #define RB_ALLOCV(v, n) \ ((n) < RUBY_ALLOCV_LIMIT ? \ ((v) = 0, alloca(n)) : \ rb_alloc_tmp_buffer(&(v), (n))) /** * Allocates a memory region, possibly on stack. If the given size exceeds * #RUBY_ALLOCV_LIMIT, it allocates a dedicated opaque ruby object instead and * let our GC sweep that region after use. Either way you can fire-and-forget. * * ```CXX * #include <sys/types.h> * * VALUE * foo(int n) * { * VALUE v; * auto ptr = RB_ALLOCV(struct tms, v, n); * ... * // no need to free `ptr`. * } * ``` * * If you want to be super-duper polite you can also explicitly state the end * of use of such memory region by calling #RB_ALLOCV_END(). * * @param type The type of array elements. * @param v A variable to hold the just-in-case opaque Ruby object. * @param n Number of elements requested to allocate. * @return An array of `n` elements of `type`. * @note `n` may be evaluated twice. */ #define RB_ALLOCV_N(type, v, n) \ RBIMPL_CAST((type *) \ (((size_t)(n) < RUBY_ALLOCV_LIMIT / sizeof(type)) ? \ ((v) = 0, alloca((n) * sizeof(type))) : \ rb_alloc_tmp_buffer2(&(v), (n), sizeof(type)))) /** * Polite way to declare that the given array is not used any longer. Calling * this not mandatory. Our GC can baby-sit you. However it is not a very bad * idea to use it when possible. Doing so could reduce memory footprint. * * @param v A variable previously passed to either #RB_ALLOCV/#RB_ALLOCV_N. */ #define RB_ALLOCV_END(v) rb_free_tmp_buffer(&(v)) /** * Handy macro to erase a region of memory. * * @param p Target pointer. * @param type Type of `p[0]` * @param n Length of `p`. * @return `p`. * @post First `n` elements of `p` are squashed. */ #define MEMZERO(p,type,n) memset((p), 0, rbimpl_size_mul_or_raise(sizeof(type), (n))) /** * Handy macro to call memcpy. * * @param p1 Destination pointer. * @param p2 Source pointer. * @param type Type of `p2[0]` * @param n Length of `p2`. * @return `p1`. * @post First `n` elements of `p2` are copied into `p1`. */ #define MEMCPY(p1,p2,type,n) ruby_nonempty_memcpy((p1), (p2), rbimpl_size_mul_or_raise(sizeof(type), (n))) /** * Handy macro to call memmove. * * @param p1 Destination pointer. * @param p2 Source pointer. * @param type Type of `p2[0]` * @param n Length of `p2`. * @return `p1`. * @post First `n` elements of `p2` are copied into `p1`. */ #define MEMMOVE(p1,p2,type,n) memmove((p1), (p2), rbimpl_size_mul_or_raise(sizeof(type), (n))) /** * Handy macro to call memcmp * * @param p1 Target LHS. * @param p2 Target RHS. * @param type Type of `p1[0]` * @param n Length of `p1`. * @retval <0 `p1` is "less" than `p2`. * @retval 0 `p1` is equal to `p2`. * @retval >0 `p1` is "greater" than `p2`. */ #define MEMCMP(p1,p2,type,n) memcmp((p1), (p2), rbimpl_size_mul_or_raise(sizeof(type), (n))) #define ALLOC_N RB_ALLOC_N /**< @old{RB_ALLOC_N} */ #define ALLOC RB_ALLOC /**< @old{RB_ALLOC} */ #define ZALLOC_N RB_ZALLOC_N /**< @old{RB_ZALLOC_N} */ #define ZALLOC RB_ZALLOC /**< @old{RB_ZALLOC} */ #define REALLOC_N RB_REALLOC_N /**< @old{RB_REALLOC_N} */ #define ALLOCV RB_ALLOCV /**< @old{RB_ALLOCV} */ #define ALLOCV_N RB_ALLOCV_N /**< @old{RB_ALLOCV_N} */ #define ALLOCV_END RB_ALLOCV_END /**< @old{RB_ALLOCV_END} */ /** * @private * * This is an implementation detail of rbimpl_size_mul_overflow(). * * @internal * * Expecting this struct to be eliminated by function inlinings. This is * nothing more than std::variant<std::size_t> if we could use recent C++, but * reality is we cannot. */ struct rbimpl_size_mul_overflow_tag { bool left; /**< Whether overflow happened or not. */ size_t right; /**< Multiplication result. */ }; RBIMPL_SYMBOL_EXPORT_BEGIN() RBIMPL_ATTR_RESTRICT() RBIMPL_ATTR_RETURNS_NONNULL() RBIMPL_ATTR_ALLOC_SIZE((2)) RBIMPL_ATTR_NONNULL(()) /** * @private * * This is an implementation detail of #RB_ALLOCV(). People don't use this * directly. * * @param[out] store Pointer to a variable. * @param[in] len Requested number of bytes to allocate. * @return Allocated `len` bytes array. * @post `store` holds the corresponding tmp buffer object. */ void *rb_alloc_tmp_buffer(volatile VALUE *store, long len); RBIMPL_ATTR_RESTRICT() RBIMPL_ATTR_RETURNS_NONNULL() RBIMPL_ATTR_ALLOC_SIZE((2,3)) RBIMPL_ATTR_NONNULL(()) /** * @private * * This is an implementation detail of #RB_ALLOCV_N(). People don't use this * directly. * * @param[out] store Pointer to a variable. * @param[in] len Requested number of bytes to allocate. * @param[in] count Number of elements in an array. * @return Allocated `len` bytes array. * @post `store` holds the corresponding tmp buffer object. * * @internal * * Although the meaning of `count` variable is clear, @shyouhei doesn't * understand its needs. */ void *rb_alloc_tmp_buffer_with_count(volatile VALUE *store, size_t len,size_t count); /** * @private * * This is an implementation detail of #RB_ALLOCV_END(). People don't use this * directly. * * @param[out] store Pointer to a variable. * @pre `store` is a NULL, or a pointer to a tmp buffer object. * @post `*store` is ::RUBY_Qfalse. * @post The object formerly stored in `store` is destroyed. */ void rb_free_tmp_buffer(volatile VALUE *store); RBIMPL_ATTR_NORETURN() /** * @private * * This is an implementation detail of #RB_ALLOCV_N(). People don't use this * directly. * * @param[in] x Arbitrary value. * @param[in] y Arbitrary value. * @exception rb_eArgError `x` * `y` would integer overflow. */ void ruby_malloc_size_overflow(size_t x, size_t y); #ifdef HAVE_RB_GC_GUARDED_PTR_VAL volatile VALUE *rb_gc_guarded_ptr_val(volatile VALUE *ptr, VALUE val); #endif RBIMPL_SYMBOL_EXPORT_END() #ifdef _MSC_VER # pragma optimize("", off) /** * @private * * This is an implementation detail of #RB_GC_GUARD(). People don't use this * directly. * * @param[in] ptr A pointer to an on-stack C variable. * @return `ptr` as-is. */ static inline volatile VALUE * rb_gc_guarded_ptr(volatile VALUE *ptr) { return ptr; } # pragma optimize("", on) #endif /** * @deprecated This function was an implementation detail of old * #RB_ALLOCV_N(). We no longer use it. @shyouhei suspects that * there are no actual usage now. However it was not marked as * private before. We cannot delete it any longer. * @param[in] a Arbitrary value. * @param[in] b Arbitrary value. * @param[in] max Possible maximum value. * @param[out] c A pointer to return the computation result. * @retval 1 `c` is insane. * @retval 0 `c` is sane. * @post `c` holds `a` * `b`, but could be overflowed. */ static inline int rb_mul_size_overflow(size_t a, size_t b, size_t max, size_t *c) { #ifdef DSIZE_T RB_GNUC_EXTENSION DSIZE_T da, db, c2; da = a; db = b; c2 = da * db; if (c2 > max) return 1; *c = RBIMPL_CAST((size_t)c2); #else if (b != 0 && a > max / b) return 1; *c = a * b; #endif return 0; } #if defined(__DOXYGEN__) RBIMPL_ATTR_CONSTEXPR(CXX14) #elif RBIMPL_COMPILER_SINCE(GCC, 7, 0, 0) RBIMPL_ATTR_CONSTEXPR(CXX14) /* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70507 */ #elif RBIMPL_COMPILER_SINCE(Clang, 7, 0, 0) RBIMPL_ATTR_CONSTEXPR(CXX14) /* https://bugs.llvm.org/show_bug.cgi?id=37633 */ #endif RBIMPL_ATTR_CONST() /** * @private * * This is an implementation detail of #RB_ALLOCV_N(). People don't use this * directly. * * @param[in] x Arbitrary value. * @param[in] y Arbitrary value. * @return `{ left, right }`, where `left` is whether there is an integer * overflow or not, and `right` is a (possibly overflowed) result * of `x` * `y`. * * @internal * * This is in fact also an implementation detail of ruby_xmalloc2() etc. */ static inline struct rbimpl_size_mul_overflow_tag rbimpl_size_mul_overflow(size_t x, size_t y) { struct rbimpl_size_mul_overflow_tag ret = { false, 0, }; #if RBIMPL_HAS_BUILTIN(__builtin_mul_overflow) ret.left = __builtin_mul_overflow(x, y, &ret.right); #elif defined(DSIZE_T) RB_GNUC_EXTENSION DSIZE_T dx = x; RB_GNUC_EXTENSION DSIZE_T dy = y; RB_GNUC_EXTENSION DSIZE_T dz = dx * dy; ret.left = dz > SIZE_MAX; ret.right = RBIMPL_CAST((size_t)dz); #elif defined(_MSC_VER) && defined(_WIN64) unsigned __int64 dp = 0; unsigned __int64 dz = _umul128(x, y, &dp); ret.left = RBIMPL_CAST((bool)dp); ret.right = RBIMPL_CAST((size_t)dz); #else /* https://wiki.sei.cmu.edu/confluence/display/c/INT30-C.+Ensure+that+unsigned+integer+operations+do+not+wrap */ ret.left = (y != 0) && (x > SIZE_MAX / y); ret.right = x * y; #endif return ret; } /** * @private * * This is an implementation detail of #RB_ALLOCV_N(). People don't use this * directly. * * @param[in] x Arbitrary value. * @param[in] y Arbitrary value. * @exception rb_eArgError Multiplication could integer overflow. * @return `x` * `y`. * * @internal * * This is in fact also an implementation detail of ruby_xmalloc2() etc. */ static inline size_t rbimpl_size_mul_or_raise(size_t x, size_t y) { struct rbimpl_size_mul_overflow_tag size = rbimpl_size_mul_overflow(x, y); if (RB_LIKELY(! size.left)) { return size.right; } else { ruby_malloc_size_overflow(x, y); RBIMPL_UNREACHABLE_RETURN(0); } } /** * This is an implementation detail of #RB_ALLOCV_N(). People don't use this * directly. * * @param[out] store Pointer to a variable. * @param[in] count Number of elements in an array. * @param[in] elsize Size of each elements. * @return Region of `count` * `elsize` bytes. * @post `store` holds the corresponding tmp buffer object. * * @internal * * We might want to deprecate this function and make a `rbimpl_` counterpart. */ static inline void * rb_alloc_tmp_buffer2(volatile VALUE *store, long count, size_t elsize) { const size_t total_size = rbimpl_size_mul_or_raise(count, elsize); const size_t cnt = (total_size + sizeof(VALUE) - 1) / sizeof(VALUE); return rb_alloc_tmp_buffer_with_count(store, total_size, cnt); } RBIMPL_SYMBOL_EXPORT_BEGIN() RBIMPL_ATTR_NOALIAS() RBIMPL_ATTR_NONNULL((1)) RBIMPL_ATTR_RETURNS_NONNULL() /* At least since 2004, glibc's <string.h> annotates memcpy to be * __attribute__((__nonnull__(1, 2))). However it is safe to pass NULL to the * source pointer, if n is 0. Let's wrap memcpy. */ static inline void * ruby_nonempty_memcpy(void *dest, const void *src, size_t n) { if (n) { return memcpy(dest, src, n); } else { return dest; } } RBIMPL_SYMBOL_EXPORT_END() #endif /* RBIMPL_MEMORY_H */
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