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分享*(void **) 与 void*的区别
阅读nginx源码时：
*(void **) conf = ctx;
其中：
void ***ctx;
void *conf;
网上找到的回答很少。
想请问一下：
*(void**) 是什么意思？
*(void **) conf = ctx;
其中：
void ***ctx;
void *conf;
网上找到的回答很少。
想请问一下：
*(void**) 是什么意思？
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lotluck 2019-10-18
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终于看到一个懂的人
赵4老师 2018-04-04
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找这个很久了，求链接。[/quote]
MSDN98_1.ISO http://pan.baidu.com/s/1dDF41ix, MSDN98_2.ISO http://pan.baidu.com/s/1bnGo0Vl
mk:@MSITStore:D:\MSDN98\98VS\2052\vclang.chm::/html/_pluslang_c.2b2b_.operators.htm
棉猴 2018-04-04
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*(void**)表示void指针的指针的解引用；void*是一种特殊的指针类型，可用于存放任意对象的地址。void**即为void类型指针的指针，void***为void类型指针的指针的指针。
解引用：操作符*可以用来对指针解引用，即表示指针所指向的内容。
请参考《指向指针的指针》
https://blog.csdn.net/hou09tian/article/details/79822073
天外怪魔 2018-04-03
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强制类型转换后取值。
之所以这样搞，是为了将ctx存入conf这个地址指向的内存。
比如conf=0x12345678，ctx=0xfefefefe。
那么操作完成后内存地址0x12345678里存的就是0xfefefefe。
天外怪魔 2018-04-03
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找这个很久了，求链接。
「已注销」 2018-04-03
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他不想对 ctx 进行强制转换，所以就对 conf 进行转换了。但如果两个都不转换，有可能警告，一个三级指针，一个一级指针。
赵4老师 2018-04-03
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仅供参考：
//C++ Operators
// Operators specify an evaluation to be performed on one of the following:
// One operand (unary operator)
// Two operands (binary operator)
// Three operands (ternary operator)
// The C++ language includes all C operators and adds several new operators.
// Table 1.1 lists the operators available in Microsoft C++.
// Operators follow a strict precedence which defines the evaluation order of
//expressions containing these operators. Operators associate with either the
//expression on their left or the expression on their right; this is called
//“associativity.” Operators in the same group have equal precedence and are
//evaluated left to right in an expression unless explicitly forced by a pair of
//parentheses, ( ).
// Table 1.1 shows the precedence and associativity of C++ operators
// (from highest to lowest precedence).
//
//Table 1.1 C++ Operator Precedence and Associativity
// The highest precedence level is at the top of the table.
//+------------------+-----------------------------------------+---------------+
//| Operator | Name or Meaning | Associativity |
//+------------------+-----------------------------------------+---------------+
//| :: | Scope resolution | None |
//| :: | Global | None |
//| [ ] | Array subscript | Left to right |
//| ( ) | Function call | Left to right |
//| ( ) | Conversion | None |
//| . | Member selection (object) | Left to right |
//| -> | Member selection (pointer) | Left to right |
//| ++ | Postfix increment | None |
//| -- | Postfix decrement | None |
//| new | Allocate object | None |
//| delete | Deallocate object | None |
//| delete[ ] | Deallocate object | None |
//| ++ | Prefix increment | None |
//| -- | Prefix decrement | None |
//| * | Dereference | None |
//| & | Address-of | None |
//| + | Unary plus | None |
//| - | Arithmetic negation (unary) | None |
//| ! | Logical NOT | None |
//| ~ | Bitwise complement | None |
//| sizeof | Size of object | None |
//| sizeof ( ) | Size of type | None |
//| typeid( ) | type name | None |
//| (type) | Type cast (conversion) | Right to left |
//| const_cast | Type cast (conversion) | None |
//| dynamic_cast | Type cast (conversion) | None |
//| reinterpret_cast | Type cast (conversion) | None |
//| static_cast | Type cast (conversion) | None |
//| .* | Apply pointer to class member (objects) | Left to right |
//| ->* | Dereference pointer to class member | Left to right |
//| * | Multiplication | Left to right |
//| / | Division | Left to right |
//| % | Remainder (modulus) | Left to right |
//| + | Addition | Left to right |
//| - | Subtraction | Left to right |
//| << | Left shift | Left to right |
//| >> | Right shift | Left to right |
//| < | Less than | Left to right |
//| > | Greater than | Left to right |
//| <= | Less than or equal to | Left to right |
//| >= | Greater than or equal to | Left to right |
//| == | Equality | Left to right |
//| != | Inequality | Left to right |
//| & | Bitwise AND | Left to right |
//| ^ | Bitwise exclusive OR | Left to right |
//| | | Bitwise OR | Left to right |
//| && | Logical AND | Left to right |
//| || | Logical OR | Left to right |
//| e1?e2:e3 | Conditional | Right to left |
//| = | Assignment | Right to left |
//| *= | Multiplication assignment | Right to left |
//| /= | Division assignment | Right to left |
//| %= | Modulus assignment | Right to left |
//| += | Addition assignment | Right to left |
//| -= | Subtraction assignment | Right to left |
//| <<= | Left-shift assignment | Right to left |
//| >>= | Right-shift assignment | Right to left |
//| &= | Bitwise AND assignment | Right to left |
//| |= | Bitwise inclusive OR assignment | Right to left |
//| ^= | Bitwise exclusive OR assignment | Right to left |
//| , | Comma | Left to right |
//+------------------+-----------------------------------------+---------------+
lunaflywar 2018-04-02
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*(void **) conf = ctx
变成
typedef void* pVoid
*(pVoid *)conf = ctx
实际是一样的，看起来比较明显
操作结果就是 把指针conf指向的第一个字节赋值为ctx
niconicobear 2018-03-31
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*(void **) conf = ctx; 这个是函数指针吧
狐狸小十 2018-03-31
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强制类型转换后取值
