Are pragma push/pop_macro directive stacks unique to each macro?

Question

Microsoft provides the following example:

// pragma_directives_pop_macro.cpp
// compile with: /W1
#include <stdio.h>
#define X 1
#define Y 2

int main() {
   printf("%d",X);
   printf(" %d",Y);
   #define Y 3   // C4005
   #pragma push_macro("Y")
   #pragma push_macro("X")
   printf(" %d",X);
   #define X 2   // C4005
   printf(" %d",X);
   #pragma pop_macro("X")
   printf(" %d",X);
   #pragma pop_macro("Y")
   printf(" %d",Y);
}

which outputs: 1 2 1 2 1 3

Is there a separate stack for macro "Y" and macro "X", or do they use the same stack for all macros?

Answer 1

Each macro has its own stack. As the documentation you link to says, push_macro “Saves the value of the macro-name macro on the top of the stack for this macro,” and pop_macro “Sets the value of the macro-name macro to the value on the top of the stack for this macro.”

We can confirm this interpretation with code that pops X and Y not in last-in-first-out-order yet recovers the values originally pushed for X and Y respectively:

#include <stdio.h>

int main(void)
{
    #define X "X0" 
    #define Y "Y0"
    printf("X=%s.\n", X);
    printf("Y=%s.\n", Y);
    #pragma push_macro("X")
    printf("Pushed X.\n");
    #pragma push_macro("Y")
    printf("Pushed Y.\n");
    #undef X
    #undef Y
    #define X "X1"
    #define Y "Y1"
    printf("X=%s.\n", X);
    printf("Y=%s.\n", Y);
    #pragma pop_macro("X")
    printf("Popped X.\n");
    #pragma pop_macro("Y")
    printf("Popped Y.\n");
    printf("X=%s.\n", X);
    printf("Y=%s.\n", Y);
}

which prints:

X=X0.
Y=Y0.
Pushed X.
Pushed Y.
X=X1.
Y=Y1.
Popped X.
Popped Y.
X=X0.
Y=Y0.