6.6.7.1 -Aquestion (answer)
Assert the answer answer for question question, in case it is tested with a preprocessing conditional such as #if #question(answer). -A- disables the standard assertions that normally describe the target machine.
For example, the function prototype for main might be declared as follows:
#if #environ(freestanding)
int main(void);
#else
int main(int argc, char *argv[]);
#endif
A -A command-line option could then be used to select between the two prototypes. For example, to select the first of the two, the following command-line option could be used:
-Aenviron(freestanding)