TIL `a ?: b`, that's actually pretty nice, a bit like Haskell's `fromMaybe b a` (or `a <|> b` if b can also b "empty")

and I do like `#define _(e...) ({e;})` – that's one where I feel the short macro name is OK. But I'd like it better if that were just how C worked from the get-go.

Very nice discussion at the end of the article. There are good things to be learnt from this code and its discussions even if you disagree with some or even most of the style.

Yes, '?:' is also known as the Elvis operator [1][2]. I sometimes use it in other languages such as Groovy. But I don't use it in C because this happens to be a GCC extension [3][4] and I've often had to compile my C projects with compilers that do not support GCC extensions. The C standard [5] defines the conditional operator as:

  conditional-expression:
    logical-OR-expression
    logical-OR-expression ? expression : conditional-expression

  expression:
    assignment-expression
    expression , assignment-expression

  assignment-expression:
    conditional-expression
    unary-expression assignment-operator assignment-expression

  unary-expression:
    postfix-expression
    ++ unary-expression
    -- unary-expression
    unary-operator cast-expression
    sizeof unary-expression
    sizeof ( type-name )
    alignof ( type-name )

  assignment-operator: one of
    = *= /= %= += -= <<= >>= &= ^= |=

  ... and so on ...

  $ cat foo.c
  int main(void) {
      if () {}
  }

  $ clang -std=c17 -pedantic -Wall -Wextra foo.c && ./a.out
  foo.c:2:9: error: expected expression
      2 |     if () {}
        |         ^
  1 error generated.

  $ cat bar.c
  #include <stdio.h>
  int main(void) {
      printf("%d\n", 0 ?: 99);
      printf("%d\n", 1 ?: 99);
  }

  $ clang -std=c17 bar.c && ./a.out
  99
  1

  $ clang -std=c17 -pedantic bar.c && ./a.out
  bar.c:3:23: warning: use of GNU ?: conditional expression extension, omitting middle operand [-Wgnu-conditional-omitted-operand]
      3 |     printf("%d\n", 0 ?: 99);
        |                       ^
  bar.c:4:23: warning: use of GNU ?: conditional expression extension, omitting middle operand [-Wgnu-conditional-omitted-operand]
      4 |     printf("%d\n", 1 ?: 99);
        |                       ^
  2 warnings generated.
  99
  1

[2] https://groovy-lang.org/operators.html#_elvis_operator

[3] https://gcc.gnu.org/onlinedocs/gcc/Syntax-Extensions.html

[4] https://gcc.gnu.org/onlinedocs/gcc/Conditionals.html

[5] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3299.pdf