Portable deprecation notice for C compilers

main.c

#ifndef __has_attribute
  #define __has_attribute(x) 0
#endif

#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L || \
    defined(__cplusplus) && __cplusplus >= 201402L
  #define CAMLdeprecated(name, replacement)               \
    [[deprecated("use '" #replacement "' instead")]]
#elif __has_attribute(deprecated) || defined(__GNUC__)
  #define CAMLdeprecated(name, replacement)                               \
    __attribute__((deprecated("use '" #replacement "' instead")))
#elif defined(_MSC_VER)
  #define CAMLdeprecated(name, replacement)                               \
    __declspec(deprecated("is deprecated, use " #replacement " instead"))
#else
  #define CAMLdeprecated(name, replacement)
#endif

#define CAMLstringify(x) #x

#if defined(__llvm__)
  #define CAMLdeprecated_macro(name, replacement)                       \
    _Pragma(CAMLstringify(GCC warning "'" #name "' is deprecated: "     \
                          "use '" #replacement "' instead"))
#elif defined(__GNUC__)
  #define CAMLmakewarning(x) CAMLstringify(GCC warning x)
  #define CAMLdeprecated_macro(name, replacement)                       \
    _Pragma(CAMLmakewarning(CAMLstringify(name is deprecated:           \
                                          use replacement instead)))
#elif defined(_MSC_VER)
  #define CAMLdefer(M,...) M(__VA_ARGS__)
  #define CAMLmakewarning(x) _Pragma(CAMLstringify(message(x)))
  #define CAMLdeprecated_macro(name, replacement)                         \
    CAMLmakewarning(__FILE__ "(" CAMLdefer(CAMLstringify,__LINE__) "): '" \
                    #name "': is deprecated, use " #replacement " instead")
#else
  #define CAMLdeprecated_macro(name, replacement)
#endif

#define CAMLdeprecated_typedef(name, type)                      \
  CAMLdeprecated_macro(CAMLdeprecated_typedef, CAMLdeprecated)  \
  CAMLdeprecated(name, unknown)                                 \
  typedef type name

typedef void * T;

struct CAMLdeprecated(S1, S2) S1 { int s; };
CAMLdeprecated(PT1, PT2) typedef T* PT1;
CAMLdeprecated_typedef(PT3, T*);
CAMLdeprecated(x1, x2) int x1 = 0;
union U { CAMLdeprecated(n1, n2) int n1; };
CAMLdeprecated(f1, f2) void f1(void) {};
enum CAMLdeprecated(E1, E2) E1 { E };

#if !defined(_MSC_VER)
enum { A1 CAMLdeprecated(A1, A2), B1 CAMLdeprecated(B1, B2) = 42 };
#endif

void h(void) {};
#define g                                       \
    CAMLdeprecated_macro(g, h)                  \
    h

int main(void) {
    struct S1 s;
    PT1 p;
    PT3 q;
    x1 = 42;
    union U u = { .n1 = 36 };
    f1();
    enum E1 e;
#if !defined(_MSC_VER)
    int a = A1;
    int b = B1;
#endif

    g();
}

/*
  - https://en.cppreference.com/w/c/language/attributes/deprecated
  - https://learn.microsoft.com/en-us/cpp/preprocessor/deprecated-c-cpp?view=msvc-170
  - https://learn.microsoft.com/en-us/cpp/cpp/deprecated-cpp?view=msvc-170
  - https://gcc.gnu.org/onlinedocs/cpp/Pragmas.html
  - https://gcc.gnu.org/onlinedocs/gcc-14.2.0/gcc/Common-Type-Attributes.html#index-deprecated-type-attribute
  - https://clang.llvm.org/docs/UsersManual.html#controlling-diagnostics-via-pragmas
 */