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Can I add a comment or line of code to a function or above so when the application is built it throws warnings if the function is used?

Posted on 2008-06-12
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Last Modified: 2013-12-13
I have seen something like this for Visual Studio, but have not tested it:
#pragma deprecated
http://msdn.microsoft.com/en-us/library/8wsycdzs(VS.71).aspx

Is there something similar for GCC or other compilers or do they recognize this?

It would be very useful to get warnings when we are using deprecated functions.
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Question by:ctangent
11 Comments
 
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by:evilrix
ID: 21769931
Some versions of gcc will warn if you use deprecated C/C++ features. Unfortunately, Microsoft went a bit mad and marked functions as deprecated when they are still valid Posix/ANSI CC++ functions.

For more on gcc see this thread: { http:Q_23478482.html }
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by:Infinity08
Infinity08 earned 800 total points
ID: 21770482
I think ctangent means that he wants to do this for his own functions. I don't know of any gcc #pragma that would do that. You could do something like this though :

        void fun() {
            /* do something */
        }

        #define fun _Pragma("\"Warning: deprecated function 'fun' called\"") fun

        int main(void) {
            fun();                      /* <--- will generate the above warning */
            return 0;
        }
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by:evilrix
ID: 21770771
>> I think ctangent means that he wants to do this for his own functions
Maybe, but I was responding to this point : "It would be very useful to get warnings when we are using deprecated functions.", which I interpreted to mean those deprecated in the standard.
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Author Comment

by:ctangent
ID: 21771119
evilrix, infinity is correct. I'm interested in calling my own functions deprecated.

Infinity08, would that method work for all compilers?

So at the top of any function I could do:

#define myfunction _Pragma("WARNING HERE") myfunction
void myfunction()
{

}
for any function and it would work (even if function takes arguments etc.
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Assisted Solution

by:jkr
jkr earned 200 total points
ID: 21771257
>>would that method work for all compilers?

#pragma directives are very compiler specific and not covered by any standard. GCC even discourages their usage (http://gcc.gnu.org/onlinedocs/gcc/Pragmas.html#Pragmas). If you want something portable, maybe the #error preprocessor directive would help.
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Expert Comment

by:evilrix
ID: 21771315
>> I'm interested in calling my own functions deprecated.
Try __attribute__ ((deprecated))
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Accepted Solution

by:
evilrix earned 1000 total points
ID: 21771325
Odd... it didn't post my example! I'll try again :)

>> I'm interested in calling my own functions deprecated.
Try __attribute__ ((deprecated))

int main()
{
        float f= 1.1f;
}
rcormier@satan:~/tmp$ cat x.cpp
#include <iostream>
 
void myfunc(int i) __attribute__ ((deprecated));
 
void myfunc(int i)
{
        std::cout << "hello" << std::endl;
}
 
int main()
{
        myfunc(0);
}

Open in new window

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by:evilrix
ID: 21771332
Arrr, now I've posted too much... undo undo!

>> I'm interested in calling my own functions deprecated.
Try __attribute__ ((deprecated))

#include <iostream>
 
void myfunc(int i) __attribute__ ((deprecated));
 
void myfunc(int i)
{
        std::cout << "hello" << std::endl;
}
 
int main()
{
        myfunc(0);
}

Open in new window

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Assisted Solution

by:evilrix
evilrix earned 1000 total points
ID: 21771337
>> __attribute__ ((deprecated))
Documentation for all function attributes: http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html
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Assisted Solution

by:Infinity08
Infinity08 earned 800 total points
ID: 21773954
>> Infinity08, would that method work for all compilers?

Difficult to say, since pragma's are completely implementation defined. It does for gcc - that I tested (and that was what your question was about if I'm not mistaken). Note that the _Pragma operator is part of C99.


>> So at the top of any function I could do:

No, it should not be seen by the function definition, or the function definition itself will generate the warning. Ie. you should place it in the header file AFTER the function declaration.


>> (even if function takes arguments etc.

Yes. It just uses the function name.



But, evilrix's __attribute__ ((deprecated)) solution is nicer :)
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Expert Comment

by:evilrix
ID: 21774112
>> evilrix's __attribute__ ((deprecated)) solution is nicer
Thanks :)

Yours was pretty neat too -- but I just decided to RTM ;)
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