/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- * vim: set ts=8 sw=4 et tw=99 ft=cpp: * * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ #ifndef js_utility_h__ #define js_utility_h__ #include "mozilla/Assertions.h" #include "mozilla/Attributes.h" #include #include #ifdef JS_OOM_DO_BACKTRACES #include #include #endif #include "jstypes.h" # include "js/TemplateLib.h" # include "mozilla/Scoped.h" /* The public JS engine namespace. */ namespace JS {} /* The mozilla-shared reusable template/utility namespace. */ namespace mozilla {} /* The private JS engine namespace. */ namespace js { /* The private namespace is a superset of the public/shared namespaces. */ using namespace JS; using namespace mozilla; } /* namespace js */ /* * Pattern used to overwrite freed memory. If you are accessing an object with * this pattern, you probably have a dangling pointer. */ #define JS_FREE_PATTERN 0xDA #define JS_ASSERT(expr) MOZ_ASSERT(expr) #define JS_ASSERT_IF(cond, expr) MOZ_ASSERT_IF(cond, expr) #define JS_NOT_REACHED(reason) MOZ_NOT_REACHED(reason) #define JS_ALWAYS_TRUE(expr) MOZ_ALWAYS_TRUE(expr) #define JS_ALWAYS_FALSE(expr) MOZ_ALWAYS_FALSE(expr) #ifdef DEBUG # ifdef JS_THREADSAFE # define JS_THREADSAFE_ASSERT(expr) JS_ASSERT(expr) # else # define JS_THREADSAFE_ASSERT(expr) ((void) 0) # endif #else # define JS_THREADSAFE_ASSERT(expr) ((void) 0) #endif #define JS_STATIC_ASSERT(cond) MOZ_STATIC_ASSERT(cond, "JS_STATIC_ASSERT") #define JS_STATIC_ASSERT_IF(cond, expr) MOZ_STATIC_ASSERT_IF(cond, expr, "JS_STATIC_ASSERT_IF") extern MOZ_NORETURN JS_PUBLIC_API(void) JS_Assert(const char *s, const char *file, int ln); /* * Abort the process in a non-graceful manner. This will cause a core file, * call to the debugger or other moral equivalent as well as causing the * entire process to stop. */ extern JS_PUBLIC_API(void) JS_Abort(void); /* * Custom allocator support for SpiderMonkey */ #if defined JS_USE_CUSTOM_ALLOCATOR # include "jscustomallocator.h" #else # ifdef DEBUG /* * In order to test OOM conditions, when the shell command-line option * |-A NUM| is passed, we fail continuously after the NUM'th allocation. */ extern JS_PUBLIC_DATA(uint32_t) OOM_maxAllocations; /* set from shell/js.cpp */ extern JS_PUBLIC_DATA(uint32_t) OOM_counter; /* data race, who cares. */ #ifdef JS_OOM_DO_BACKTRACES #define JS_OOM_BACKTRACE_SIZE 32 static JS_ALWAYS_INLINE void PrintBacktrace() { void* OOM_trace[JS_OOM_BACKTRACE_SIZE]; char** OOM_traceSymbols = NULL; int32_t OOM_traceSize = 0; int32_t OOM_traceIdx = 0; OOM_traceSize = backtrace(OOM_trace, JS_OOM_BACKTRACE_SIZE); OOM_traceSymbols = backtrace_symbols(OOM_trace, OOM_traceSize); if (!OOM_traceSymbols) return; for (OOM_traceIdx = 0; OOM_traceIdx < OOM_traceSize; ++OOM_traceIdx) { fprintf(stderr, "#%d %s\n", OOM_traceIdx, OOM_traceSymbols[OOM_traceIdx]); } free(OOM_traceSymbols); } #define JS_OOM_EMIT_BACKTRACE() \ do {\ fprintf(stderr, "Forcing artificial memory allocation function failure:\n");\ PrintBacktrace();\ } while (0) # else # define JS_OOM_EMIT_BACKTRACE() do {} while(0) #endif /* JS_OOM_DO_BACKTRACES */ # define JS_OOM_POSSIBLY_FAIL() \ do \ { \ if (++OOM_counter > OOM_maxAllocations) { \ JS_OOM_EMIT_BACKTRACE();\ return NULL; \ } \ } while (0) # define JS_OOM_POSSIBLY_FAIL_REPORT(cx) \ do \ { \ if (++OOM_counter > OOM_maxAllocations) { \ JS_OOM_EMIT_BACKTRACE();\ js_ReportOutOfMemory(cx);\ return NULL; \ } \ } while (0) # else # define JS_OOM_POSSIBLY_FAIL() do {} while(0) # define JS_OOM_POSSIBLY_FAIL_REPORT(cx) do {} while(0) # endif /* DEBUG */ static JS_INLINE void* js_malloc(size_t bytes) { JS_OOM_POSSIBLY_FAIL(); return malloc(bytes); } static JS_INLINE void* js_calloc(size_t bytes) { JS_OOM_POSSIBLY_FAIL(); return calloc(bytes, 1); } static JS_INLINE void* js_realloc(void* p, size_t bytes) { JS_OOM_POSSIBLY_FAIL(); return realloc(p, bytes); } static JS_INLINE void js_free(void* p) { free(p); } #endif/* JS_USE_CUSTOM_ALLOCATOR */ JS_BEGIN_EXTERN_C /* * Replace bit-scanning code sequences with CPU-specific instructions to * speedup calculations of ceiling/floor log2. * * With GCC 3.4 or later we can use __builtin_clz for that, see bug 327129. * * SWS: Added MSVC intrinsic bitscan support. See bugs 349364 and 356856. */ #if defined(_WIN32) && (_MSC_VER >= 1300) && (defined(_M_IX86) || defined(_M_AMD64) || defined(_M_X64)) unsigned char _BitScanForward(unsigned long * Index, unsigned long Mask); unsigned char _BitScanReverse(unsigned long * Index, unsigned long Mask); # pragma intrinsic(_BitScanForward,_BitScanReverse) __forceinline static int __BitScanForward32(unsigned int val) { unsigned long idx; _BitScanForward(&idx, (unsigned long)val); return (int)idx; } __forceinline static int __BitScanReverse32(unsigned int val) { unsigned long idx; _BitScanReverse(&idx, (unsigned long)val); return (int)(31-idx); } # define js_bitscan_ctz32(val) __BitScanForward32(val) # define js_bitscan_clz32(val) __BitScanReverse32(val) # define JS_HAS_BUILTIN_BITSCAN32 #if defined(_M_AMD64) || defined(_M_X64) unsigned char _BitScanForward64(unsigned long * Index, unsigned __int64 Mask); unsigned char _BitScanReverse64(unsigned long * Index, unsigned __int64 Mask); # pragma intrinsic(_BitScanForward64,_BitScanReverse64) __forceinline static int __BitScanForward64(unsigned __int64 val) { unsigned long idx; _BitScanForward64(&idx, val); return (int)idx; } __forceinline static int __BitScanReverse64(unsigned __int64 val) { unsigned long idx; _BitScanReverse64(&idx, val); return (int)(63-idx); } # define js_bitscan_ctz64(val) __BitScanForward64(val) # define js_bitscan_clz64(val) __BitScanReverse64(val) # define JS_HAS_BUILTIN_BITSCAN64 #endif #elif (__GNUC__ >= 4) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) # define js_bitscan_ctz32(val) __builtin_ctz(val) # define js_bitscan_clz32(val) __builtin_clz(val) # define JS_HAS_BUILTIN_BITSCAN32 # if (JS_BYTES_PER_WORD == 8) # define js_bitscan_ctz64(val) __builtin_ctzll(val) # define js_bitscan_clz64(val) __builtin_clzll(val) # define JS_HAS_BUILTIN_BITSCAN64 # endif #endif /* ** Macro version of JS_CeilingLog2: Compute the log of the least power of ** 2 greater than or equal to _n. The result is returned in _log2. */ #ifdef JS_HAS_BUILTIN_BITSCAN32 /* * Use intrinsic function or count-leading-zeros to calculate ceil(log2(_n)). * The macro checks for "n <= 1" and not "n != 0" as js_bitscan_clz32(0) is * undefined. */ # define JS_CEILING_LOG2(_log2,_n) \ JS_BEGIN_MACRO \ unsigned int j_ = (unsigned int)(_n); \ (_log2) = (j_ <= 1 ? 0 : 32 - js_bitscan_clz32(j_ - 1)); \ JS_END_MACRO #else # define JS_CEILING_LOG2(_log2,_n) \ JS_BEGIN_MACRO \ uint32_t j_ = (uint32_t)(_n); \ (_log2) = 0; \ if ((j_) & ((j_)-1)) \ (_log2) += 1; \ if ((j_) >> 16) \ (_log2) += 16, (j_) >>= 16; \ if ((j_) >> 8) \ (_log2) += 8, (j_) >>= 8; \ if ((j_) >> 4) \ (_log2) += 4, (j_) >>= 4; \ if ((j_) >> 2) \ (_log2) += 2, (j_) >>= 2; \ if ((j_) >> 1) \ (_log2) += 1; \ JS_END_MACRO #endif /* ** Macro version of JS_FloorLog2: Compute the log of the greatest power of ** 2 less than or equal to _n. The result is returned in _log2. ** ** This is equivalent to finding the highest set bit in the word. */ #ifdef JS_HAS_BUILTIN_BITSCAN32 /* * Use js_bitscan_clz32 or count-leading-zeros to calculate floor(log2(_n)). * Since js_bitscan_clz32(0) is undefined, the macro set the loweset bit to 1 * to ensure 0 result when _n == 0. */ # define JS_FLOOR_LOG2(_log2,_n) \ JS_BEGIN_MACRO \ (_log2) = 31 - js_bitscan_clz32(((unsigned int)(_n)) | 1); \ JS_END_MACRO #else # define JS_FLOOR_LOG2(_log2,_n) \ JS_BEGIN_MACRO \ uint32_t j_ = (uint32_t)(_n); \ (_log2) = 0; \ if ((j_) >> 16) \ (_log2) += 16, (j_) >>= 16; \ if ((j_) >> 8) \ (_log2) += 8, (j_) >>= 8; \ if ((j_) >> 4) \ (_log2) += 4, (j_) >>= 4; \ if ((j_) >> 2) \ (_log2) += 2, (j_) >>= 2; \ if ((j_) >> 1) \ (_log2) += 1; \ JS_END_MACRO #endif #if JS_BYTES_PER_WORD == 4 # ifdef JS_HAS_BUILTIN_BITSCAN32 # define js_FloorLog2wImpl(n) \ ((size_t)(JS_BITS_PER_WORD - 1 - js_bitscan_clz32(n))) # else JS_PUBLIC_API(size_t) js_FloorLog2wImpl(size_t n); # endif #elif JS_BYTES_PER_WORD == 8 # ifdef JS_HAS_BUILTIN_BITSCAN64 # define js_FloorLog2wImpl(n) \ ((size_t)(JS_BITS_PER_WORD - 1 - js_bitscan_clz64(n))) # else JS_PUBLIC_API(size_t) js_FloorLog2wImpl(size_t n); # endif #else # error "NOT SUPPORTED" #endif JS_END_EXTERN_C /* * Internal function. * Compute the log of the least power of 2 greater than or equal to n. This is * a version of JS_CeilingLog2 that operates on unsigned integers with * CPU-dependant size. */ #define JS_CEILING_LOG2W(n) ((n) <= 1 ? 0 : 1 + JS_FLOOR_LOG2W((n) - 1)) /* * Internal function. * Compute the log of the greatest power of 2 less than or equal to n. * This is a version of JS_FloorLog2 that operates on unsigned integers with * CPU-dependant size and requires that n != 0. */ static MOZ_ALWAYS_INLINE size_t JS_FLOOR_LOG2W(size_t n) { JS_ASSERT(n != 0); return js_FloorLog2wImpl(n); } /* * JS_ROTATE_LEFT32 * * There is no rotate operation in the C Language so the construct (a << 4) | * (a >> 28) is used instead. Most compilers convert this to a rotate * instruction but some versions of MSVC don't without a little help. To get * MSVC to generate a rotate instruction, we have to use the _rotl intrinsic * and use a pragma to make _rotl inline. * * MSVC in VS2005 will do an inline rotate instruction on the above construct. */ #if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_AMD64) || \ defined(_M_X64)) #include #pragma intrinsic(_rotl) #define JS_ROTATE_LEFT32(a, bits) _rotl(a, bits) #else #define JS_ROTATE_LEFT32(a, bits) (((a) << (bits)) | ((a) >> (32 - (bits)))) #endif #include /* * Low-level memory management in SpiderMonkey: * * ** Do not use the standard malloc/free/realloc: SpiderMonkey allows these * to be redefined (via JS_USE_CUSTOM_ALLOCATOR) and Gecko even #define's * these symbols. * * ** Do not use the builtin C++ operator new and delete: these throw on * error and we cannot override them not to. * * Allocation: * * - If the lifetime of the allocation is tied to the lifetime of a GC-thing * (that is, finalizing the GC-thing will free the allocation), call one of * the following functions: * * JSContext::{malloc_,realloc_,calloc_,new_} * JSRuntime::{malloc_,realloc_,calloc_,new_} * * These functions accumulate the number of bytes allocated which is used as * part of the GC-triggering heuristic. * * The difference between the JSContext and JSRuntime versions is that the * cx version reports an out-of-memory error on OOM. (This follows from the * general SpiderMonkey idiom that a JSContext-taking function reports its * own errors.) * * - Otherwise, use js_malloc/js_realloc/js_calloc/js_free/js_new * * Deallocation: * * - Ordinarily, use js_free/js_delete. * * - For deallocations during GC finalization, use one of the following * operations on the FreeOp provided to the finalizer: * * FreeOp::{free_,delete_} * * The advantage of these operations is that the memory is batched and freed * on another thread. */ #define JS_NEW_BODY(allocator, t, parms) \ void *memory = allocator(sizeof(t)); \ return memory ? new(memory) t parms : NULL; /* * Given a class which should provide 'new' methods, add * JS_DECLARE_NEW_METHODS (see JSContext for a usage example). This * adds news with up to 12 parameters. Add more versions of new below if * you need more than 12 parameters. * * Note: Do not add a ; at the end of a use of JS_DECLARE_NEW_METHODS, * or the build will break. */ #define JS_DECLARE_NEW_METHODS(NEWNAME, ALLOCATOR, QUALIFIERS)\ template \ QUALIFIERS T *NEWNAME() {\ JS_NEW_BODY(ALLOCATOR, T, ())\ }\ \ template \ QUALIFIERS T *NEWNAME(P1 p1) {\ JS_NEW_BODY(ALLOCATOR, T, (p1))\ }\ \ template \ QUALIFIERS T *NEWNAME(P1 p1, P2 p2) {\ JS_NEW_BODY(ALLOCATOR, T, (p1, p2))\ }\ \ template \ QUALIFIERS T *NEWNAME(P1 p1, P2 p2, P3 p3) {\ JS_NEW_BODY(ALLOCATOR, T, (p1, p2, p3))\ }\ \ template \ QUALIFIERS T *NEWNAME(P1 p1, P2 p2, P3 p3, P4 p4) {\ JS_NEW_BODY(ALLOCATOR, T, (p1, p2, p3, p4))\ }\ \ template \ QUALIFIERS T *NEWNAME(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5) {\ JS_NEW_BODY(ALLOCATOR, T, (p1, p2, p3, p4, p5))\ }\ \ template \ QUALIFIERS T *NEWNAME(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6) {\ JS_NEW_BODY(ALLOCATOR, T, (p1, p2, p3, p4, p5, p6))\ }\ \ template \ QUALIFIERS T *NEWNAME(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7) {\ JS_NEW_BODY(ALLOCATOR, T, (p1, p2, p3, p4, p5, p6, p7))\ }\ \ template \ QUALIFIERS T *NEWNAME(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7, P8 p8) {\ JS_NEW_BODY(ALLOCATOR, T, (p1, p2, p3, p4, p5, p6, p7, p8))\ }\ \ template \ QUALIFIERS T *NEWNAME(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7, P8 p8, P9 p9) {\ JS_NEW_BODY(ALLOCATOR, T, (p1, p2, p3, p4, p5, p6, p7, p8, p9))\ }\ \ template \ QUALIFIERS T *NEWNAME(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7, P8 p8, P9 p9, P10 p10) {\ JS_NEW_BODY(ALLOCATOR, T, (p1, p2, p3, p4, p5, p6, p7, p8, p9, p10))\ }\ \ template \ QUALIFIERS T *NEWNAME(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7, P8 p8, P9 p9, P10 p10, P11 p11) {\ JS_NEW_BODY(ALLOCATOR, T, (p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11))\ }\ \ template \ QUALIFIERS T *NEWNAME(P1 p1, P2 p2, P3 p3, P4 p4, P5 p5, P6 p6, P7 p7, P8 p8, P9 p9, P10 p10, P11 p11, P12 p12) {\ JS_NEW_BODY(ALLOCATOR, T, (p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12))\ }\ JS_DECLARE_NEW_METHODS(js_new, js_malloc, static JS_ALWAYS_INLINE) template static JS_ALWAYS_INLINE void js_delete(T *p) { if (p) { p->~T(); js_free(p); } } template static JS_ALWAYS_INLINE T * js_pod_malloc() { return (T *)js_malloc(sizeof(T)); } template static JS_ALWAYS_INLINE T * js_pod_calloc() { return (T *)js_calloc(sizeof(T)); } template static JS_ALWAYS_INLINE T * js_pod_malloc(size_t numElems) { if (numElems & js::tl::MulOverflowMask::result) return NULL; return (T *)js_malloc(numElems * sizeof(T)); } template static JS_ALWAYS_INLINE T * js_pod_calloc(size_t numElems) { if (numElems & js::tl::MulOverflowMask::result) return NULL; return (T *)js_calloc(numElems * sizeof(T)); } namespace js { template struct ScopedFreePtrTraits { typedef T* type; static T* empty() { return NULL; } static void release(T* ptr) { js_free(ptr); } }; SCOPED_TEMPLATE(ScopedFreePtr, ScopedFreePtrTraits) template struct ScopedDeletePtrTraits : public ScopedFreePtrTraits { static void release(T *ptr) { js_delete(ptr); } }; SCOPED_TEMPLATE(ScopedDeletePtr, ScopedDeletePtrTraits) } /* namespace js */ /* * The following classes are designed to cause assertions to detect * inadvertent use of guard objects as temporaries. In other words, * when we have a guard object whose only purpose is its constructor and * destructor (and is never otherwise referenced), the intended use * might be: * JSAutoTempValueRooter tvr(cx, 1, &val); * but is is easy to accidentally write: * JSAutoTempValueRooter(cx, 1, &val); * which compiles just fine, but runs the destructor well before the * intended time. * * They work by adding (#ifdef DEBUG) an additional parameter to the * guard object's constructor, with a default value, so that users of * the guard object's API do not need to do anything. The default value * of this parameter is a temporary object. C++ (ISO/IEC 14882:1998), * section 12.2 [class.temporary], clauses 4 and 5 seem to assume a * guarantee that temporaries are destroyed in the reverse of their * construction order, but I actually can't find a statement that that * is true in the general case (beyond the two specific cases mentioned * there). However, it seems to be true. * * These classes are intended to be used only via the macros immediately * below them: * JS_DECL_USE_GUARD_OBJECT_NOTIFIER declares (ifdef DEBUG) a member * variable, and should be put where a declaration of a private * member variable would be placed. * JS_GUARD_OBJECT_NOTIFIER_PARAM should be placed at the end of the * parameters to each constructor of the guard object; it declares * (ifdef DEBUG) an additional parameter. * JS_GUARD_OBJECT_NOTIFIER_INIT is a statement that belongs in each * constructor. It uses the parameter declared by * JS_GUARD_OBJECT_NOTIFIER_PARAM. */ #ifdef DEBUG class JS_FRIEND_API(JSGuardObjectNotifier) { private: bool* mStatementDone; public: JSGuardObjectNotifier() : mStatementDone(NULL) {} ~JSGuardObjectNotifier() { *mStatementDone = true; } void setStatementDone(bool *aStatementDone) { mStatementDone = aStatementDone; } }; class JS_FRIEND_API(JSGuardObjectNotificationReceiver) { private: bool mStatementDone; public: JSGuardObjectNotificationReceiver() : mStatementDone(false) {} ~JSGuardObjectNotificationReceiver() { /* * Assert that the guard object was not used as a temporary. * (Note that this assert might also fire if Init is not called * because the guard object's implementation is not using the * above macros correctly.) */ JS_ASSERT(mStatementDone); } void Init(const JSGuardObjectNotifier &aNotifier) { /* * aNotifier is passed as a const reference so that we can pass a * temporary, but we really intend it as non-const */ const_cast(aNotifier). setStatementDone(&mStatementDone); } }; #define JS_DECL_USE_GUARD_OBJECT_NOTIFIER \ JSGuardObjectNotificationReceiver _mCheckNotUsedAsTemporary; #define JS_GUARD_OBJECT_NOTIFIER_PARAM \ , const JSGuardObjectNotifier& _notifier = JSGuardObjectNotifier() #define JS_GUARD_OBJECT_NOTIFIER_PARAM_NO_INIT \ , const JSGuardObjectNotifier& _notifier #define JS_GUARD_OBJECT_NOTIFIER_PARAM0 \ const JSGuardObjectNotifier& _notifier = JSGuardObjectNotifier() #define JS_GUARD_OBJECT_NOTIFIER_INIT \ JS_BEGIN_MACRO _mCheckNotUsedAsTemporary.Init(_notifier); JS_END_MACRO #else /* defined(DEBUG) */ #define JS_DECL_USE_GUARD_OBJECT_NOTIFIER #define JS_GUARD_OBJECT_NOTIFIER_PARAM #define JS_GUARD_OBJECT_NOTIFIER_PARAM_NO_INIT #define JS_GUARD_OBJECT_NOTIFIER_PARAM0 #define JS_GUARD_OBJECT_NOTIFIER_INIT JS_BEGIN_MACRO JS_END_MACRO #endif /* !defined(DEBUG) */ namespace js { /* * "Move" References * * Some types can be copied much more efficiently if we know the original's * value need not be preserved --- that is, if we are doing a "move", not a * "copy". For example, if we have: * * Vector u; * Vector v(u); * * the constructor for v must apply a copy constructor to each element of u --- * taking time linear in the length of u. However, if we know we will not need u * any more once v has been initialized, then we could initialize v very * efficiently simply by stealing u's dynamically allocated buffer and giving it * to v --- a constant-time operation, regardless of the size of u. * * Moves often appear in container implementations. For example, when we append * to a vector, we may need to resize its buffer. This entails moving each of * its extant elements from the old, smaller buffer to the new, larger buffer. * But once the elements have been migrated, we're just going to throw away the * old buffer; we don't care if they still have their values. So if the vector's * element type can implement "move" more efficiently than "copy", the vector * resizing should by all means use a "move" operation. Hash tables also need to * be resized. * * The details of the optimization, and whether it's worth applying, vary from * one type to the next. And while some constructor calls are moves, many really * are copies, and can't be optimized this way. So we need: * * 1) a way for a particular invocation of a copy constructor to say that it's * really a move, and that the value of the original isn't important * afterwards (althought it must still be safe to destroy); and * * 2) a way for a type (like Vector) to announce that it can be moved more * efficiently than it can be copied, and provide an implementation of that * move operation. * * The Move(T &) function takes a reference to a T, and returns an MoveRef * referring to the same value; that's 1). An MoveRef is simply a reference * to a T, annotated to say that a copy constructor applied to it may move that * T, instead of copying it. Finally, a constructor that accepts an MoveRef * should perform a more efficient move, instead of a copy, providing 2). * * So, where we might define a copy constructor for a class C like this: * * C(const C &rhs) { ... copy rhs to this ... } * * we would declare a move constructor like this: * * C(MoveRef rhs) { ... move rhs to this ... } * * And where we might perform a copy like this: * * C c2(c1); * * we would perform a move like this: * * C c2(Move(c1)) * * Note that MoveRef implicitly converts to T &, so you can pass an * MoveRef to an ordinary copy constructor for a type that doesn't support a * special move constructor, and you'll just get a copy. This means that * templates can use Move whenever they know they won't use the original value * any more, even if they're not sure whether the type at hand has a specialized * move constructor. If it doesn't, the MoveRef will just convert to a T &, * and the ordinary copy constructor will apply. * * A class with a move constructor can also provide a move assignment operator, * which runs this's destructor, and then applies the move constructor to * *this's memory. A typical definition: * * C &operator=(MoveRef rhs) { * this->~C(); * new(this) C(rhs); * return *this; * } * * With that in place, one can write move assignments like this: * * c2 = Move(c1); * * This destroys c1, moves c1's value to c2, and leaves c1 in an undefined but * destructible state. * * This header file defines MoveRef and Move in the js namespace. It's up to * individual containers to annotate moves as such, by calling Move; and it's up * to individual types to define move constructors. * * One hint: if you're writing a move constructor where the type has members * that should be moved themselves, it's much nicer to write this: * * C(MoveRef c) : x(c->x), y(c->y) { } * * than the equivalent: * * C(MoveRef c) { new(&x) X(c->x); new(&y) Y(c->y); } * * especially since GNU C++ fails to notice that this does indeed initialize x * and y, which may matter if they're const. */ template class MoveRef { public: typedef T Referent; explicit MoveRef(T &t) : pointer(&t) { } T &operator*() const { return *pointer; } T *operator->() const { return pointer; } operator T& () const { return *pointer; } private: T *pointer; }; template MoveRef Move(T &t) { return MoveRef(t); } template MoveRef Move(const T &t) { return MoveRef(const_cast(t)); } /* Useful for implementing containers that assert non-reentrancy */ class ReentrancyGuard { /* ReentrancyGuard is not copyable. */ ReentrancyGuard(const ReentrancyGuard &); void operator=(const ReentrancyGuard &); #ifdef DEBUG bool &entered; #endif public: template #ifdef DEBUG ReentrancyGuard(T &obj) : entered(obj.entered) #else ReentrancyGuard(T &/*obj*/) #endif { #ifdef DEBUG JS_ASSERT(!entered); entered = true; #endif } ~ReentrancyGuard() { #ifdef DEBUG entered = false; #endif } }; /* * Round x up to the nearest power of 2. This function assumes that the most * significant bit of x is not set, which would lead to overflow. */ JS_ALWAYS_INLINE size_t RoundUpPow2(size_t x) { return size_t(1) << JS_CEILING_LOG2W(x); } /* Integral types for all hash functions. */ typedef uint32_t HashNumber; const unsigned HashNumberSizeBits = 32; namespace detail { /* * Given a raw hash code, h, return a number that can be used to select a hash * bucket. * * This function aims to produce as uniform an output distribution as possible, * especially in the most significant (leftmost) bits, even though the input * distribution may be highly nonrandom, given the constraints that this must * be deterministic and quick to compute. * * Since the leftmost bits of the result are best, the hash bucket index is * computed by doing ScrambleHashCode(h) / (2^32/N) or the equivalent * right-shift, not ScrambleHashCode(h) % N or the equivalent bit-mask. * * FIXME: OrderedHashTable uses a bit-mask; see bug 775896. */ inline HashNumber ScrambleHashCode(HashNumber h) { /* * Simply returning h would not cause any hash tables to produce wrong * answers. But it can produce pathologically bad performance: The caller * right-shifts the result, keeping only the highest bits. The high bits of * hash codes are very often completely entropy-free. (So are the lowest * bits.) * * So we use Fibonacci hashing, as described in Knuth, The Art of Computer * Programming, 6.4. This mixes all the bits of the input hash code h. * * The value of goldenRatio is taken from the hex * expansion of the golden ratio, which starts 1.9E3779B9.... * This value is especially good if values with consecutive hash codes * are stored in a hash table; see Knuth for details. */ static const HashNumber goldenRatio = 0x9E3779B9U; return h * goldenRatio; } } /* namespace detail */ } /* namespace js */ namespace JS { /* * Methods for poisoning GC heap pointer words and checking for poisoned words. * These are in this file for use in Value methods and so forth. * * If the moving GC hazard analysis is in use and detects a non-rooted stack * pointer to a GC thing, one byte of that pointer is poisoned to refer to an * invalid location. For both 32 bit and 64 bit systems, the fourth byte of the * pointer is overwritten, to reduce the likelihood of accidentally changing * a live integer value. */ inline void PoisonPtr(void *v) { #if defined(JSGC_ROOT_ANALYSIS) && defined(DEBUG) uint8_t *ptr = (uint8_t *) v + 3; *ptr = JS_FREE_PATTERN; #endif } template inline bool IsPoisonedPtr(T *v) { #if defined(JSGC_ROOT_ANALYSIS) && defined(DEBUG) uint32_t mask = uintptr_t(v) & 0xff000000; return mask == uint32_t(JS_FREE_PATTERN << 24); #else return false; #endif } } /* * This is SpiderMonkey's equivalent to |nsMallocSizeOfFun|. */ typedef size_t(*JSMallocSizeOfFun)(const void *p); /* sixgill annotation defines */ #ifndef HAVE_STATIC_ANNOTATIONS # define HAVE_STATIC_ANNOTATIONS # ifdef XGILL_PLUGIN # define STATIC_PRECONDITION(COND) __attribute__((precondition(#COND))) # define STATIC_PRECONDITION_ASSUME(COND) __attribute__((precondition_assume(#COND))) # define STATIC_POSTCONDITION(COND) __attribute__((postcondition(#COND))) # define STATIC_POSTCONDITION_ASSUME(COND) __attribute__((postcondition_assume(#COND))) # define STATIC_INVARIANT(COND) __attribute__((invariant(#COND))) # define STATIC_INVARIANT_ASSUME(COND) __attribute__((invariant_assume(#COND))) # define STATIC_PASTE2(X,Y) X ## Y # define STATIC_PASTE1(X,Y) STATIC_PASTE2(X,Y) # define STATIC_ASSERT(COND) \ JS_BEGIN_MACRO \ __attribute__((assert_static(#COND), unused)) \ int STATIC_PASTE1(assert_static_, __COUNTER__); \ JS_END_MACRO # define STATIC_ASSUME(COND) \ JS_BEGIN_MACRO \ __attribute__((assume_static(#COND), unused)) \ int STATIC_PASTE1(assume_static_, __COUNTER__); \ JS_END_MACRO # define STATIC_ASSERT_RUNTIME(COND) \ JS_BEGIN_MACRO \ __attribute__((assert_static_runtime(#COND), unused)) \ int STATIC_PASTE1(assert_static_runtime_, __COUNTER__); \ JS_END_MACRO # else /* XGILL_PLUGIN */ # define STATIC_PRECONDITION(COND) /* nothing */ # define STATIC_PRECONDITION_ASSUME(COND) /* nothing */ # define STATIC_POSTCONDITION(COND) /* nothing */ # define STATIC_POSTCONDITION_ASSUME(COND) /* nothing */ # define STATIC_INVARIANT(COND) /* nothing */ # define STATIC_INVARIANT_ASSUME(COND) /* nothing */ # define STATIC_ASSERT(COND) JS_BEGIN_MACRO /* nothing */ JS_END_MACRO # define STATIC_ASSUME(COND) JS_BEGIN_MACRO /* nothing */ JS_END_MACRO # define STATIC_ASSERT_RUNTIME(COND) JS_BEGIN_MACRO /* nothing */ JS_END_MACRO # endif /* XGILL_PLUGIN */ # define STATIC_SKIP_INFERENCE STATIC_INVARIANT(skip_inference()) #endif /* HAVE_STATIC_ANNOTATIONS */ #endif /* js_utility_h__ */