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gecko-dev/js/public/Utility.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sts=4 et sw=4 tw=99:
* 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 "mozilla/Compiler.h"
#include "mozilla/Move.h"
#include "mozilla/Scoped.h"
#include "mozilla/TemplateLib.h"
#include "mozilla/UniquePtr.h"
#include <stdlib.h>
#include <string.h>
#ifdef JS_OOM_DO_BACKTRACES
#include <execinfo.h>
#include <stdio.h>
#endif
#include "jstypes.h"
/* The public JS engine namespace. */
namespace JS {}
/* The mozilla-shared reusable template/utility namespace. */
namespace mozilla {}
/* The private JS engine namespace. */
namespace js {}
/*
* Patterns used by SpiderMonkey to overwrite unused memory. If you are
* accessing an object with one of these pattern, you probably have a dangling
* pointer.
*/
#define JS_FRESH_NURSERY_PATTERN 0x2F
#define JS_SWEPT_NURSERY_PATTERN 0x2B
#define JS_ALLOCATED_NURSERY_PATTERN 0x2D
#define JS_FRESH_TENURED_PATTERN 0x4F
#define JS_MOVED_TENURED_PATTERN 0x49
#define JS_SWEPT_TENURED_PATTERN 0x4B
#define JS_ALLOCATED_TENURED_PATTERN 0x4D
#define JS_EMPTY_STOREBUFFER_PATTERN 0x1B
#define JS_SWEPT_CODE_PATTERN 0x3B
#define JS_SWEPT_FRAME_PATTERN 0x5B
#define JS_STATIC_ASSERT(cond) 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 MOZ_COLD JS_PUBLIC_API(void)
JS_Assert(const char* s, const char* file, int ln);
/*
* Custom allocator support for SpiderMonkey
*/
#if defined JS_USE_CUSTOM_ALLOCATOR
# include "jscustomallocator.h"
#else
# if defined(DEBUG) || defined(JS_OOM_BREAKPOINT)
/*
* In order to test OOM conditions, when the testing function
* oomAfterAllocations COUNT is passed, we fail continuously after the NUM'th
* allocation from now.
*/
extern JS_PUBLIC_DATA(uint32_t) OOM_maxAllocations; /* set in builtin/TestingFunctions.cpp */
extern JS_PUBLIC_DATA(uint32_t) OOM_counter; /* data race, who cares. */
#ifdef JS_OOM_BREAKPOINT
static MOZ_NEVER_INLINE void js_failedAllocBreakpoint() { asm(""); }
#define JS_OOM_CALL_BP_FUNC() js_failedAllocBreakpoint()
#else
#define JS_OOM_CALL_BP_FUNC() do {} while(0)
#endif
# define JS_OOM_POSSIBLY_FAIL() \
do \
{ \
if (++OOM_counter > OOM_maxAllocations) { \
JS_OOM_CALL_BP_FUNC();\
return nullptr; \
} \
} while (0)
# define JS_OOM_POSSIBLY_FAIL_BOOL() \
do \
{ \
if (++OOM_counter > OOM_maxAllocations) { \
JS_OOM_CALL_BP_FUNC();\
return false; \
} \
} while (0)
namespace js {
namespace oom {
static inline bool ShouldFailWithOOM()
{
if (++OOM_counter > OOM_maxAllocations) {
JS_OOM_CALL_BP_FUNC();
return true;
}
return false;
}
}
}
# else
# define JS_OOM_POSSIBLY_FAIL() do {} while(0)
# define JS_OOM_POSSIBLY_FAIL_BOOL() do {} while(0)
namespace js { namespace oom { static inline bool ShouldFailWithOOM() { return false; } } }
# endif /* DEBUG || JS_OOM_BREAKPOINT */
static inline void* js_malloc(size_t bytes)
{
JS_OOM_POSSIBLY_FAIL();
return malloc(bytes);
}
static inline void* js_calloc(size_t bytes)
{
JS_OOM_POSSIBLY_FAIL();
return calloc(bytes, 1);
}
static inline void* js_calloc(size_t nmemb, size_t size)
{
JS_OOM_POSSIBLY_FAIL();
return calloc(nmemb, size);
}
static inline void* js_realloc(void* p, size_t bytes)
{
JS_OOM_POSSIBLY_FAIL();
return realloc(p, bytes);
}
static inline void js_free(void* p)
{
free(p);
}
static inline char* js_strdup(const char* s)
{
JS_OOM_POSSIBLY_FAIL();
return strdup(s);
}
#endif/* JS_USE_CUSTOM_ALLOCATOR */
#include <new>
/*
* 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.
*/
/*
* Given a class which should provide a 'new' method, add
* JS_DECLARE_NEW_METHODS (see js::MallocProvider for an example).
*
* 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 <class T, typename... Args> \
QUALIFIERS T * \
NEWNAME(Args&&... args) MOZ_HEAP_ALLOCATOR { \
void* memory = ALLOCATOR(sizeof(T)); \
return memory \
? new(memory) T(mozilla::Forward<Args>(args)...) \
: nullptr; \
}
/*
* Given a class which should provide 'make' methods, add
* JS_DECLARE_MAKE_METHODS (see js::MallocProvider for an example). This
* method is functionally the same as JS_DECLARE_NEW_METHODS: it just declares
* methods that return mozilla::UniquePtr instances that will singly-manage
* ownership of the created object.
*
* Note: Do not add a ; at the end of a use of JS_DECLARE_MAKE_METHODS,
* or the build will break.
*/
#define JS_DECLARE_MAKE_METHODS(MAKENAME, NEWNAME, QUALIFIERS)\
template <class T, typename... Args> \
QUALIFIERS mozilla::UniquePtr<T, JS::DeletePolicy<T>> \
MAKENAME(Args&&... args) MOZ_HEAP_ALLOCATOR { \
T* ptr = NEWNAME<T>(mozilla::Forward<Args>(args)...); \
return mozilla::UniquePtr<T, JS::DeletePolicy<T>>(ptr); \
}
JS_DECLARE_NEW_METHODS(js_new, js_malloc, static MOZ_ALWAYS_INLINE)
template <class T>
static MOZ_ALWAYS_INLINE void
js_delete(T* p)
{
if (p) {
p->~T();
js_free(p);
}
}
template<class T>
static MOZ_ALWAYS_INLINE void
js_delete_poison(T* p)
{
if (p) {
p->~T();
memset(p, 0x3B, sizeof(T));
js_free(p);
}
}
template <class T>
static MOZ_ALWAYS_INLINE T*
js_pod_malloc()
{
return (T*)js_malloc(sizeof(T));
}
template <class T>
static MOZ_ALWAYS_INLINE T*
js_pod_calloc()
{
return (T*)js_calloc(sizeof(T));
}
template <class T>
static MOZ_ALWAYS_INLINE T*
js_pod_malloc(size_t numElems)
{
if (MOZ_UNLIKELY(numElems & mozilla::tl::MulOverflowMask<sizeof(T)>::value))
return nullptr;
return (T*)js_malloc(numElems * sizeof(T));
}
template <class T>
static MOZ_ALWAYS_INLINE T*
js_pod_calloc(size_t numElems)
{
if (MOZ_UNLIKELY(numElems & mozilla::tl::MulOverflowMask<sizeof(T)>::value))
return nullptr;
return (T*)js_calloc(numElems * sizeof(T));
}
template <class T>
static MOZ_ALWAYS_INLINE T*
js_pod_realloc(T* prior, size_t oldSize, size_t newSize)
{
MOZ_ASSERT(!(oldSize & mozilla::tl::MulOverflowMask<sizeof(T)>::value));
if (MOZ_UNLIKELY(newSize & mozilla::tl::MulOverflowMask<sizeof(T)>::value))
return nullptr;
return (T*)js_realloc(prior, newSize * sizeof(T));
}
namespace js {
template<typename T>
struct ScopedFreePtrTraits
{
typedef T* type;
static T* empty() { return nullptr; }
static void release(T* ptr) { js_free(ptr); }
};
SCOPED_TEMPLATE(ScopedJSFreePtr, ScopedFreePtrTraits)
template <typename T>
struct ScopedDeletePtrTraits : public ScopedFreePtrTraits<T>
{
static void release(T* ptr) { js_delete(ptr); }
};
SCOPED_TEMPLATE(ScopedJSDeletePtr, ScopedDeletePtrTraits)
template <typename T>
struct ScopedReleasePtrTraits : public ScopedFreePtrTraits<T>
{
static void release(T* ptr) { if (ptr) ptr->release(); }
};
SCOPED_TEMPLATE(ScopedReleasePtr, ScopedReleasePtrTraits)
} /* namespace js */
namespace JS {
template<typename T>
struct DeletePolicy
{
void operator()(T* ptr) {
js_delete(ptr);
}
};
struct FreePolicy
{
void operator()(void* ptr) {
js_free(ptr);
}
};
} // namespace JS
namespace js {
/* Integral types for all hash functions. */
typedef uint32_t HashNumber;
const unsigned HashNumberSizeBits = 32;
typedef mozilla::UniquePtr<char, JS::FreePolicy> UniqueChars;
static inline UniqueChars make_string_copy(const char* str)
{
return UniqueChars(js_strdup(str));
}
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 */
/* 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 */
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