How do you to get this warning?

We have a custom CMake toolchain that sets -Wformat=2 in the CMAKE_C_FLAGS.

What if someone has a toolchain or process which relies on trapping that?

AFAIU the compiler warning was added to not pass a user-controlled format string to printf like in this example:

void log(const char* msg) {
  printf(msg); // use printf("%s", msg) instead
}

As heuristic for non-user controlled strings the compiler looks for a string literal (which is always compile-time defined). But here in dprintf_formatf the format string is assembled on-the-fly but still not user-controlled. This renders the compiler warning into a false-positive because the format string is not user-controlled.

To suppress the warning we save all the enabled warnings, disable the format-nonliteral warning and after the function call restore all the warnings.

I cannot think of a case where one would like to see the warning anyways.

Thanks!