19 Jun
2008
19 Jun
'08
1:27 p.m.
Hi,
Julien Claassen wrote:
Hi!
The errors on lines 318 and 319 disappeared. So the Char** are
correctly declared, now as const char**. BUT now I get an error on the
next line, because the
newCDKSelection function from the CDK doesn't accept const char**, but
char** and this is not deprecated, but an "invalid conversion".
To be 100% correct you have to make a copy first!
char *title = strdup("my title");
newCDKSelection([parameters],title,[more parameters]);
....
free(title);
should do the trick.
If you can guarantee that newCDKSelection() never ever changes the
contents of the string you could just cast way the const:
const char *title = "my title";
newCDKSelection([parameters],const_cast<char *>(title),[more parameters]);
How did the GCC people think I could avoid such
things.
gcc is not the problem here. Your code is wrong. So it is in fact not a
warning but a fundamental problem :-) See below...
Note: The newCDKSelection also takes a char*
parameter, which of
course is converted in a deprecated manner if I write:
newCDKSelection([parameters],"my title",[more parameters]);
String literals ("my title") in C++ are by definition const char *
pointers. Why? Because they are subject to string pooling for example.
const char *foo = "Hello world!";
const char *bar = "Hello world!";
Depending on the optimization of the compiler foo and bar might point to
the same location.
strcpy((char *)foo, "Bad idea");
... is a bad idea because it will change foo and bar. Depending on the
compiler you might also crash because the strings could be in a read
only section.
So I tried
this:
char* title;
strcpy("my title",title);
This still won't work correctly.
Because it should be the other way round:
strcpy(title, "my title");
Please note that you have to allocate memory for title first. strdup()
is the function you're really looking for.
I guess I can live with those
warnings, but the two relevant questions are:
1. How long?
Until next version of gcc maybe? :-)
2. Do I like to live with it?
Probably you should just fix the bugs ;-)
ah does this have to be so complicated? :-(
Kindest regards and still all suggestions are wellcome!
Are you sure you need to compile your code using g++? If you don't use
any c++ then just use gcc and the problem will magically go away because
strings in C are plain char * pointers.
Best,
Florian