Ignoring return values in C

Question

Lately, I started using lint for static code analysis. One of the warning I get sometimes is regarding this issue. Let\'s say for instance that I\'ve got the following funct

Answer 1

Usually there are not too many functions the value of which you want to ignore. Splint, for example, allows to add a special comment that would let it know, that a return value of a specific function might be ignored. Unfortunately, this in effect disables all 'ignored returned value' warning related to that particular function.

Here is an example of Splint-clean program:

#include 

FILE /*@alt void@*/ *fopen(const char *path, const char *mode);

static int /*@alt void@*/ test(void)
{
   printf( "test called\n" );

   fopen( "test", "a" );

   return 0;
}

int main(void)
{  
   test();

   return 0;
}

The unpleasant part is that you need to add an additional prototype to a system function with a comment somewhere.

Btw,by default Splint doesn't complain about the return value of printf and of some other libc functions being unused. However, a stricter mode can be activated.

LINT allows something similar, but I have never used it. Here is what a documentation says.

LINT lets you mark functions with optional return values by using a directive similar to the #directives of the C preprocessor.

#pragma optresult

can be placed immediately before the definition of a function that returns an optional result. LINT then recognizes that this function returns a result that can be ignored; LINT does not give error messages if the result is ignored.