rcseacord/cmp_int

C implementation of C++ Utility functions https://en.cppreference.com/w/cpp/utility/intcmp

cmp_int's Issues

Uses gcc extension

({ }) expressions are a gcc extension.

This is not necessary because all of that can be done in a single expression with nested ?: conditional.

integer types

Claiming that this works for "integer types" is kind of weird because it seems that by design it doesn't work for char and bool. I am not questionning that design, but then this should be made cristal clear in the documentation.

does not work for extended or bit-precise integer types

The case listing in the macros is quite restrictive. I think better would be something like

#define is_signed(X)    \
_Generic((X),               \
   bool: 0,                    \
   char: (char)-1 < 0,    \
   signed char: 1,         \
   signed short 1,         \
   unsigned char: 0,    \
   unsigned short: 0,   \
   default: (0 ? (X)%1 : -1) < 0 \
)

That ensures to work also for __int128 or other such wild animals if they exist, and to give the expected answer for char if the user has a concept of "could hold negative values" for being a signed type.

cmp_equal is wrong for LHS is negative:

See: https://godbolt.org/z/YsdG8Wc7n

If you do:
cmp_equal(-5, (unsigned)5);
The result is a true value (or any case where the LHS is negative and the RHS is unsigned).

The probelm is that line 67((lhs) < 0 || make_unsigned(lhs) == (rhs) : \ should really be:
(lhs) >=0 && make_unsigned(lhs) == (rhs) : \

side effects of some expressions are doubled

int x = 0;
puts(cmp_less(x++, 0U) ? "true" : "false");
printf("%d\n", x);

Outputs:

false
2

Which can be fixed using statement expression, but statement expressions are non-standard.

naming conventions

your code should stick to one single name prefix

Support more than just the standard integer types in is_supported_type, is_signed, and make_unsigned

besides the naming convention issue, this macro is superfluous and restricts the usage of your macros to the 6 standard integer types

expressions have type `int`

The C++ variant has bool return types. This should be the same, here. Just add a cast in front of the whole expression.