warning C4305: 'argument' : truncation from 'bool *' to 'bool'

[chiwing]

bool __stdcall check_expiry_date_file(wstring filename,bool cutrun);

int std__call happy()
{
  check_expiry_date_file ( filename, &cutrun); // warning C4305: 'argument' : truncation from 'bool *' to 'bool'
//warning C4800: 'bool *' : forcing value to bool 'true' or 'false' (performance warning)
}

bool check_expiry_date_file(wstring filename,bool cutrun)
{

return(false);
}

compile warning,
what's wrong , thanks

[Disch]

I'm assuming cutrun is a bool.

check_expiry_date_file takes a bool as a parameter. If cutrun is a bool, then you'd pass it with just cutrun, not with &cutrun. &cutrun gives you a pointer to a bool.

[chiwing]

hi , Dusch
because i need to pass value back to happy(), so i use &, if don't use & , then it can not achieve what i want them to do ~~

hope i haven't misunderstand your meaning~ ~

[Disch]

If you want your check_expiry_date_file function to change 'cutrun' in the calling fuction (in this case, happy), you need to pass it by reference or by pointer. Currently you are passing by value which does not do what you want.

Here's an example of your options:

void ByVal(int v)
{
  v = 1;
}

void ByRef(int& v)
{
  v = 2;
}

void ByPtr(int* v)
{
  *v = 3;
}

void TestFunction()
{
  int test = 0;

  ByVal(test);
  cout << test;  // outputs '0' (test not changed because it was passed by value)

  ByRef(test);
  cout << test;  // outputs '2' (test changed)

  ByPtr(&test);
  cout << test;  // outputs '3' (test changed)
}

Therefore you probably want to change check_expiry_date_file so that it passes cutrun by reference or by pointer, not by value.

EDIT: stupid typos

[chiwing]

OH , thanks for Disch

that means i need to add a * in front of cutrun at called function~ ~ --> no warning now

but i want to ask

do i need to do it (add * in front of parameter of function which haven't & )

everytime when i use pass by reference~ ~

don't the default is pass by Value ? (that means * already)

i don't understand why & at caller, the value will not be show in it?

i already use pass by reference

[Disch]

I'm afraid I don't quite understand what you are asking.

If you forget a * or & somewhere, the compiler will throw an error or warning, so you'll know if you're doing it wrong.