Valgrind的 - 可能丟失警告

我有代碼如下：Valgrind的 - 可能丟失警告

std::string myName = "BLABLABLA"; 

//check if there are illegal characters 
for (unsigned int i = 0; i < myName.length(); i++) 
{ 
    const char& c = myName[i]; 
    if (!(isalnum(c) || (c == '_') || (c == '-'))) 
    { 
     return 0; 
    }  

}

這是的valgrind中的線的輸出「常量字符& C = MYNAME [I];」

==17249== 51 bytes in 1 blocks are possibly lost in loss record 116 of 224 
==17249== at 0x4C2714E: operator new(unsigned long) (vg_replace_malloc.c:261) 
==17249== by 0x602A498: std::string::_Rep::_S_create(unsigned long, unsigned long,  
std::allocator<char> const&) (in /usr/lib64/libstdc++.so.6.0.16) 
==17249== by 0x602A689: std::string::_M_mutate(unsigned long, unsigned long, 
unsigned long) (in /usr/lib64/libstdc++.so.6.0.16) 
==17249== by 0x602AFB5: std::string::_M_leak_hard() (in 
/usr/lib64/libstdc++.so.6.0.16) 
==17249== by 0x602B0A4: std::string::operator[](unsigned long) (in/
/usr/lib64/libstdc++.so.6.0.16)

我看不出什麼錯這個......

來源

2012-09-26 Kam

魔鬼在細節中。更具體地說，在GCC的'std :: string'裏面。這不是你的錯。這不是你的錯。 –

@KerrekSB gcc的字符串泄漏？ –

@LuchianGrigore：是的。這是refcount業務... –

是的，這是可怕的COW實現！您還可以強制使用const的（因此非不同誘變）超載，像這樣：

std::string const myName = "BLABLABLA"; 

//check if there are illegal characters 
for (unsigned int i = 0; i < myName.length(); i++) 
{ 
    const char& c = myName[i]; 
    if (!(isalnum(c) || (c == '_') || (c == '-'))) 
    { 
     return 0; 
    }  
}

或者（如果你不想修改原始字符串類型）：

std::string myName = "BLABLABLA"; 
std::string const &cref = myName; 
//check if there are illegal characters 
for (unsigned int i = 0; i < myName.length(); i++) 
{ 
    const char& c = cref[i]; 
    if (!(isalnum(c) || (c == '_') || (c == '-'))) 
    { 
     return 0; 
    }  
}

等

COW reference，因爲我知道我會寫一些有關它的地方。

來源

2012-09-26 15:10:39 Useless

Valgrind的 - 可能丟失警告

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