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Why should C++ programmers minimize use of 'new'?
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There are two widely-used memory allocation techniques: automatic allocation and dynamic allocation. Commonly, there is a corresponding region of memory for each: the stack and the heap.
Stack
The stack always allocates memory in a sequential fashion. It c...
What are Runtime.getRuntime().totalMemory() and freeMemory()?
...hy there is a totalMemory() AND a maxMemory(). The answer is that the JVM allocates memory lazily. Lets say you start your Java process as such:
java -Xms64m -Xmx1024m Foo
Your process starts with 64mb of memory, and if and when it needs more (up to 1024m), it will allocate memory. totalMemory...
Use of alloc init instead of new
...ere are a bunch of reasons here: http://macresearch.org/difference-between-alloc-init-and-new
Some selected ones are:
new doesn't support custom initializers (like initWithString)
alloc-init is more explicit than new
General opinion seems to be that you should use whatever you're comfortable wi...
What uses are there for “placement new”?
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Placement new allows you to construct an object in memory that's already allocated.
You may want to do this for optimization when you need to construct multiple instances of an object, and it is faster not to re-allocate memory each time you need a new instance. Instead, it might be more efficien...
How to allocate aligned memory only using the standard library?
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Original answer
{
void *mem = malloc(1024+16);
void *ptr = ((char *)mem+16) & ~ 0x0F;
memset_16aligned(ptr, 0, 1024);
free(mem);
}
Fixed answer
{
void *mem = malloc(1024+15);
void *ptr = ((uintptr_t)mem+15) & ~ (uintptr_t)0x0...
Oracle 11.2.0.4 RAC FOR redhat 6.4 - 数据库(内核) - 清泛网 - 专注C/C++及内核技术
...成修改语句：
Sql代码
1.select 'alter table '||table_name||' allocate extent;' from user_tables where num_rows=0
然后就在结果窗口里面生成了下面那些东西：
Sql代码
1.alter table E2USER_STATE allocate extent;
2.alter table ENTERPRISE_E2USER allocat...
How does delete[] “know” the size of the operand array?
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When you allocate memory on the heap, your allocator will keep track of how much memory you have allocated. This is usually stored in a "head" segment just before the memory that you get allocated. That way when it's time to free the ...
C++ new int[0] — will it allocate memory?
... When the value of the expression in a direct-new-declarator is zero, the allocation function is called to allocate an array with no elements.
From 3.7.3.1/2
The effect of dereferencing a pointer returned as a request for zero size is undefined.
Also
Even if the size of the space reques...
STL中map容器使用自定义key类型报错详解 - C/C++ - 清泛网 - 专注C/C++及内核技术
...对正在编译的类 模板 实例化“std::_Tmap_traits<_Kty,_Ty,_Pr,_Alloc,_Mfl>”的引用
1> with
1> [
1> _Kty=a,
1> _Ty=int,
1> _Pr=std::less<a>,
1> _Alloc=std::allocator<std::pair<const a,int>>,
1> _Mf...
What's the Hi/Lo algorithm?
...erability with other 3rd-party clients that are not aware of this sequence allocation strategy.
Being both efficient and interoperable with other systems, the pooled-lo optimizer is a much better candidate than the legacy hi/lo identifier strategy.
...