How can I hide "defined but not used" warnings in GCC?
GccWarningsCompiler WarningsGcc Problem Overview
I have a bunch of compile time asserts, such as:
CASSERT(isTrue) or CASSERT2(isTrue, prefix_)
When compiling with GCC I get many warnings like 'prefix_LineNumber' defined but not used
. Is there a way I can hide warnings for compile time asserts? I had no luck searching the GCC documentation. I thought I might have the var automatically used globally inside the same macro but I couldn't think of any way to do it.
Does anyone know of a way to hide that warning in GCC?
Gcc Solutions
Solution 1 - Gcc
Just saw this thread while searching for solutions to this problem. I post here for completeness the solution I found...
The GCC compiler flags that control unused warnings include:
-Wunused-function
-Wunused-label
-Wunused-parameter
-Wunused-value
-Wunused-variable
-Wunused (=all of the above)
Each of these has a corresponding negative form with "no-" inserted after the W which turns off the warning (in case it was turned on by -Wall, for example). Thus, in your case you should use
-Wno-unused-function
Of course this works for the whole code, not just compile-time asserts. For function-specific behaviour, have a look at Function attributes.
Solution 2 - Gcc
Solution for GCC not causing conflicts with other compilers
#ifdef __GNUC__
#define VARIABLE_IS_NOT_USED __attribute__ ((unused))
#else
#define VARIABLE_IS_NOT_USED
#endif
int VARIABLE_IS_NOT_USED your_variable;
Solution 3 - Gcc
This is one of the most anoying warnings, although I undestand that it may useful (sometimes) to check dead code. But I usually have static functions for debugging, or functions that maybe useful sometime in the future, or that are only used temporaly, and I want to keep them in the code.
Fortunately this warning does not care about inline functions.
inline static foo()
{
}
Solution 4 - Gcc
You can create a null statement and cast the result to void. This is portable across compilers, and gcc will not give you any warnings, even with -Wall
and -Wextra
enabled. For example:
int var; // var is not used
(void)var; // null statement, cast to void -- suppresses warning
A common technique is to create a macro for this:
#define UNUSED(x) ((void)(x))
int var;
UNUSED(var);
Solution 5 - Gcc
#define UNUSED_VAR __attribute__ ((unused))
for any variable just use the above macro before its type for example:
UNUSED_VAR int a = 2;
Solution 6 - Gcc
Wrap this functions by the following directives All the code that will be placed between push and pop will not warn you about unused functions. All the rest of the code (outside push and pop) will not be affected.
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
... your code
#pragma GCC diagnostic pop
Solution 7 - Gcc
This is hard to answer without knowing the details of your static assert macros. Perhaps you could change to a different macro to avoid this problem? You could either add the 'unused' attribute to the macro as was suggested, or you could use a different form of CASSERT().
Here are descriptions of a few alternatives:
<http://www.jaggersoft.com/pubs/CVu11_3.html>
<http://blog.kowalczyk.info/kb/compile-time-asserts-in-c.html>
<http://www.pixelbeat.org/programming/gcc/static_assert.html>
Solution 8 - Gcc
How about -Wunused-label
?