Concise way to disable specific warning instances in Clang

Question

Suppose there is some warning in my code, e.g. that Clang has added padding to a struct. I am find with that particular instance and I want to mark it as "Noted; don't warn me about this instance again".

Is there a way to do this that isn't insanely verbose (i.e. #pragma clang diagnostic push etc)? Ideally something like a comment on the same line as the warning, something like this:

// clang(-Wno-padded)

To be clear, I only want to suppress one specific instance of the warning (which normally requires #pragma diagnostic push/pop), not all warnings in the file.

Answer 1

If you have some include file where you can put a macro definition like this:

#define DO_PRAGMA(x) _Pragma(#x)
#define NOWARN(warnoption, ...)                    \
    DO_PRAGMA(GCC diagnostic push)                 \
    DO_PRAGMA(GCC diagnostic ignored #warnoption)  \
    __VA_ARGS__                                    \
    DO_PRAGMA(GCC diagnostic pop)

Then you can disable a warning within your code like this:

NOWARN(-Wpadded,
// your code for which the warning gets suppressed 
)

Example: https://godbolt.org/z/oW87ej

---

Slightly off-topic note:

gcc does not allow GCC diagnostic .... pragmas within expressions. So something like this:

#define MY_MYCRO(type) NOWARN(-Wpadded, sizeof(struct{char c; type t;}))
int myval = MY_MYCRO(int);

will produce a error in gcc and won't compile. Note: Using clang diagnostic .... pragmas will not produce an error in gcc (but also doesn't disable the warning in gcc).

Answer 2

As described in the Controlling Diagnostics via Pragmas article it would be:

#pragma clang diagnostic ignored "-Wpadded"

If you want to suppress a warning in a certain chunk of code (be it a single line of code or multiple statements) then you need to utilize the push / pop mechanism:

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wpadded"
// your code for which the warning gets suppressed 
#pragma clang diagnostic pop
// not suppressed here