Converting form CString to const char*

Question

I've wrote a method that convert form CString to const char *:

const char* CAESDlg::ConvertToChar(CString str) {
    CStringA charstr(str);
    const char *cstr = (const char *)charstr;
    return cstr;
}

but when trying to put it in a const char * it doesn't return the correct value!

const char *test = ConvertToChar(filePath);

while debugging cstr contains a valid value , but in this line const char *test = ConvertToChar(filePath); it equal a wrong value — Ahmed Ali, Apr 25 '15 at 09:29
Your function is returning a dangling pointer. What are you actually trying to do? — Alan Stokes, Apr 25 '15 at 09:45
I've a CString that i want to convert to const char * to pass it to a method that take const char * — Ahmed Ali, Apr 25 '15 at 09:48

MikeMB · Answer 1 · 2015-04-25T09:56:24.730

1

Without knowing CString and CStringA I can only guess, but it seems as if you are returning a pointer to a local variable, which is UB, as soon as you access value the pointer points to.

If you want to use a CString object as a const char* parameter you probably want to use LPCTSTR instead of your self-written ConvertToChar function.

edited Apr 25 '15 at 09:56

answered Apr 25 '15 at 09:30

MikeMB

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@AhmedAli: There are multiple possibilities, depending on how you want to use the function, but personally I'd suggest not to use `const char*` at all, but `std::string`. Btw: you should probably have a look at [this question](http://stackoverflow.com/questions/859304/convert-cstring-to-const-char) – MikeMB Apr 25 '15 at 09:43
@AhmedAli: See my edit in response to the information in your comments. – MikeMB Apr 25 '15 at 09:57
i got this error while trying to use LPCTSTR a value of type LPCTSTR can't be used to initialize an entity of type const char * – Ahmed Ali Apr 25 '15 at 10:11

score 1 · Accepted Answer · answered Apr 25 '15 at 10:30

The value of charstr gets destroyed at the end of the function before the caller assigns it to variable.

You don't need a function, the caller can use CStringA directly and note that test is valid before sFilePathA goes out of scope.

CStringA sFilePathA(filePath);
const char *test = sFilePathA;

Converting form CString to const char*

2 Answers2