C++ STL 映射无法识别 key

Question

我有这段代码，CBString 只是我用于某些处理的字符串类

  char * scrummyconfigure::dosub(strtype input)
  {
    CBString tstring;
    tstring = input;
    uint begin;
    uint end;

    begin = tstring.findchr('$');
    end = tstring.findchr('}',begin);        

    CBString k = tstring.midstr(begin+2,end-2); // this is BASE
    strtype vname = (strtype) ((const unsigned char*)k);
    strtype bvar = (strtype) "BASE";
    assert(strcmp(bvar,vname) == 0); // this never fails
    // theconf is just a struct with the map subvars
    // subvars is a map<const char *, const char *>
    out(theconf->subvars[bvar]); // always comes up with the value
    out(theconf->subvars[vname]); // always empty

    uint size = end - begin;
    tstring.remove(begin, size);

    return (const char *)tstring; // it's OKAY! it's got an overload that does things correctly
    //inline operator const char* () const { return (const char *)data; } <-- this is how it is declared in the header of the library
  }

为什么 strcmp 总是说字符串相同，但只有我声明为 bvar 的变量返回任何内容？

Answer 1

我假设 strtype 是按以下方式定义的:

typedef char * strtype

您的问题是您假设 vname 和 bvar 具有相同的值，而实际上，它们具有不同的值，每个值都指向包含相同数据的内存块。

std::map 愚蠢地将它们与 == 进行比较，我敢打赌您会发现，如果将它们与 == 进行比较，您会如预期的那样得到 false。您为什么不使用 std::string 类？

编辑:我重写了你的方法以减少恐惧:

// implied using namespace std;
string ScrummyConfigure::removeVariableOrSomething(string tstring)
{
    uint begin; // I'll assume uint is a typedef to unsigned int
    uint end;

    begin = tstring.find('$', 0);
    end = tstring.find('}', begin);        

    string vname = tstring.substr(begin + 2, end - 2); // this is supposedly BASE
    assert(vname == "BASE"); // this should be true if vname actually is BASE

    out(this->conf->subvars[bvar]);  // wherever theconf used to be, its now a member
    out(this->conf->subvars[vname]); // of ScrummyConfigure and its been renamed to conf

    uint size = end - begin;
    tstring.erase(begin, size);

    return tstring; // no casting necessary
}