字符常量* const的* const的varName的

Question

我有一個具有以下簽名的方法：

size_t advanceToNextRuleEntryRelatedIndex(size_t index, size_t nStrings, char const *const *const strings) 

我該如何解讀這樣的：char const *const *const strings？

謝謝， Pavan。

Answer 1

char const *const *const strings,strings是指向char指針的指針。如果沒有const預選賽就應該是這樣的：

char **strings; 

的const預選賽禁止在非關聯的特定級別修改提領值：

**strings = (char) something1; // not allowed because of the first const 
*strings = (char *) something2; // not allowed because of the second const 
strings = (char **) something3; // not allowed because of the third const 

換句話說，第三常量說，指針本身是不可變的，第二個const說指向指針是不可變的，第一個指出指向的字符是不可變的。

Answer 2

關鍵字const在此關鍵字後面聲明一個常量。 準則解釋勝於言：

/////// Test-code. Place anywhere in global space in C/C++ code, step with debugger 
char a1[] = "test1"; 
char a2[] = "test2"; 

char *data[2] = {a1,a2}; 

// Nothing const, change letters in words, replace words, re-point to other block of words 
char **string = &data[0]; 

// Can't change letters in words, but replace words, re-point to other block of words 
const char **string1 = (const char **) &data[0]; 
// Can neither change letters in words, not replace words, but re-point to other block of words 
const char * const* string2 = (const char * const*) &data[0]; 
// Can change nothing, however I don't understand the meaning of the 2nd const 
const char const* const* const string3 = (const char const* const* const) &data[0]; 


int foo() 
{ 

    // data in debugger is:    {"test1","test2"} 
    **string = 'T';   //data is now {"Test1","test2"} 
    //1 **string1 = 'T'; //Compiler error: you cannot assign to a variable that is const (VS2008) 
    *string1=a2;   //data is now {"test2","test2"} 
    //2 **string2='T';  //Compiler error: you cannot assign to a variable that is const (VS2008) 
    //3 *string2=a2;  //Compiler error: you cannot assign to a variable that is const (VS2008) 
    string2=string1; 

    //4 **string3='T';  //Compiler error: you cannot assign to a variable that is const (VS2008) 
    //5 *string3=a2;  //Compiler error: you cannot assign to a variable that is const (VS2008) 
    //6 string3=string1; //Compiler error: you cannot assign to a variable that is const (VS2008) 
    return 0; 
} 

static int dummy = foo(); 

/////// END OF Test-code 

Answer 3

char const *const *const strings 
^ v ^v ^v 
| | | | | | 
+----- +--+ +--+ 

所以基本上就意味着所有的指針和指針指向是常量字符串，這意味着該函數不能修改傳遞的字符串以任何方式（除非它被鑄造）。

例如

char* p{"string1","string2"}; 

其中將衰減成char **

傳遞時

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