Thread: Warning when building!

I get a warning when building my app and I wonder:

Does a build warning always means that something is wrong and MUST be redone? The reason I ask is because my app always get 1 warning when building but runs exactly as it should (as far as I know)?

Maybe a dumb question...

Usually, Error's must be fixed, warning's will not stop you compiling, but you should look closely at the warning, they're generally there for a reason, you can usually write the code a bit better and eliminate the warning (but not always, sometimes you just have to have something your compiler doesn't like).

In most cases you should NOT ignore a warning and times that you are getting a warning yet the program still works, usually means that you didn't do something explicitly so the compiler does it for you (such as implicit conversions between datatypes where data will be lost or not explicitly returning 0,etc.). If that's the case then don't ignore the warning, just explicitly write what you want to do (it will make your code more clear, anyways)! Certain warnings you can ignore such as an identifier's name being too long to store with debug information, but other than things like that, "fix" your code!

Originally posted by Polymorphic OOP
In most cases you should NOT ignore a warning and times that you are getting a warning yet the program still works, usually means that you didn't do something explicitly so the compiler does it for you (such as implicit conversions between datatypes where data will be lost or not explicitly returning 0,etc.). If that's the case then don't ignore the warning, just explicitly write what you want to do (it will make your code more clear, anyways)! Certain warnings you can ignore such as an identifier's name being too long to store with debug information, but other than things like that, "fix" your code!

Ok, what do you say about my warning:

warning: assignment makes integer from pointer without a cast

* (int *) thru_ptr = map[PartIndex]+4;

The code is running as it should but I don't like the warning every time I build.

It sounds as though you made map an array of pointers rather than an array of integers. If that is really what you want, then you'll have to explicitly convert:

* (int *) thru_ptr = (int)(map[PartIndex]+4 );

If not, it might just be your compiler acting funny. Post the declaration for map.

Originally posted by Polymorphic OOP
It sounds as though you made map an array of pointers rather than an array of integers. If that is really what you want, then you'll have to explicitly convert:

* (int *) thru_ptr = (int)(map[PartIndex]+4 );

If not, it might just be your compiler acting funny. Post the declaration for map.

unsigned char **map = NULL;

yup, that was the problem!

map[someint]

will give you a pointer to an unsigned char, NOT an integer. The fix I posted will get rid of the warning, but i guarantee that your logic is flawed on what you are doing. Your compiler was right in giving you that warning -- the statement doesn't make any logical sense. Rethink what you are trying to do.

Originally posted by Polymorphic OOP
yup, that was the problem!

map[someint]

will give you a pointer to an unsigned char, NOT an integer. The fix I posted will get rid of the warning, but i guarantee that your logic is flawed on what you are doing. Your compiler was right in giving you that warning -- the statement doesn't make any logical sense. Rethink what you are trying to do.

I have tried the line you posted now and it does not give me any warning, nice :-)

And even better, my app still does exactly the same thing.

But I don't understand what you mean by:
Rethink what you are trying to do. Do you mean that I am still doing the wrong thing even after I have used your fix? Can you please explain? Maybe it's just that my mother language is not English ;-)

Because right now you are storing the memory location of a variable to an integer, which you should pretty much never have to do. You most-likely want map's declaration to be

unsigned char* map = NULL;

instead. Post how you are using it to be certain. Don't use my fix simply because it gets rid of the warning. You have problems in your logic in the program.

Originally posted by Polymorphic OOP
Because right now you are storing the memory location of a variable to an integer, which you should pretty much never have to do. You most-likely want map's declaration to be

unsigned char* map = NULL;

instead. Post how you are using it to be certain. Don't use my fix simply because it gets rid of the warning. You have problems in your logic in the program.

Ok, I will try to explain how I use it:

My app is a MIDI sequencer made for Mac OS X and CoreMIDI.

At startup my app allocates a memory area to store 1024 pointers like this:

// allocate space for 1024 pointers, 32 bit * 1024 = 4096 bytes
if((map = malloc(sizeof(*map) * 1024)) == NULL)
{
printf("malloc map failed\n");
return 1;
}

Every time I press the record button my app allocates a memory area (a part). Everything that I play on my keyboard is stored in that memory area, but:

The first 32 bits of that memory area (the line you helped me with) is a pointer that is used to remember the current position when playing back my MIDI events (every part have a pointer). It works like this:

The pointer points to the first byte after the pointer itself. It's just a nice way of storing my pointer that way. And the timestamp values (64 bit) and MIDI values (8 bit) is stored after that. And I terminate my recording with 0xFFFFFFFFFFFFFFFF. Why you might wonder, because 0xFFFFFFFFFFFFFFFF is a easy way to stop the pointer to move any futher.

Feel free to ask if you don't understand what I am trying to explain.

In that case, you should be doing this:

unsigned char* thru_ptr;

thru_ptr = map+PartIndex+1;

Originally posted by Polymorphic OOP
In that case, you should be doing this:

unsigned char* thru_ptr;

thru_ptr = map+PartIndex+1;

That gave me a warning:

warning: assignment makes integer from pointer without a cast

Originally posted by electrolove
That gave me a warning:

warning: assignment makes integer from pointer without a cast

I got 2 errors and 6 warnings as a result of that, heh

yup, my mistake, sorry about that. It's too late at night here, heh

unsigned char* thru_ptr;

thru_ptr = map[PartIndex]+1;

Why were you adding 4!? that would put you four pointers ahead, not 1 pointer ahead. Pointer arithmetic goes by the size of the type being pointed to. Using + 1 will move you sizeof( unsigned char* ) bytes ahead, which will usually be 4 bytes. If you add 4 like your example, you'd actually be adding 4 * sizeof( unsigned char* ) bytes, whihc would usually be 16 bytes.

Originally posted by Polymorphic OOP
yup, my mistake, sorry about that. It's too late at night here, heh

unsigned char* thru_ptr;

thru_ptr = map[PartIndex]+1;

Why were you adding 4!? that would put you four pointers ahead, not 1 pointer ahead. Pointer arithmetic goes by the size of the type being pointed to. Using + 1 will move you sizeof( unsigned char* ) bytes ahead, which will usually be 4 bytes. If you add 4 like your example, you'd actually be adding 4 * sizeof( unsigned char* ) bytes, whihc would usually be 16 bytes.

testing testing, hold on...