#!/bin/sh
set -eu
base="${TMPDIR-/tmp}/mcpu-cpp-va-opt-$$"
mkdir -p "$base"
trap 'rm -rf "$base"' EXIT HUP INT TERM

cat > "$base/main.c" <<'EOT'
#define EMPTY
#define X 123
#define xy RESCANNED
#define HAS(...) __VA_OPT__(yes)
#define COMMA(format, ...) call(format __VA_OPT__(,) __VA_ARGS__)
#define STR(...) #__VA_OPT__(__VA_ARGS__)
#define STRFIX(a, ...) #__VA_OPT__(a __VA_ARGS__)
#define STRPASTE(a, ...) #__VA_OPT__(a ## z)
#define LEFT(...) pre ## __VA_OPT__(__VA_ARGS__)
#define RIGHT(...) __VA_OPT__(__VA_ARGS__) ## post
#define INNER(a, ...) __VA_OPT__(a ## y)
#define BALANCED(...) __VA_OPT__((a, (b, c)))
#define EMPTY_LEFT(...) x ## __VA_OPT__()
#define EMPTY_RIGHT(...) __VA_OPT__() ## y
#define TEXT(...) "__VA_OPT__(not syntax)" __VA_OPT__(ok)

[HAS()]
[HAS(EMPTY)]
[HAS(token)]
COMMA("zero")
COMMA("two", X, 7)
STR()
STR(X)
STRFIX(X, y)
STRPASTE(X, y)
LEFT()
LEFT(X)
RIGHT()
RIGHT(X)
INNER(x, token)
BALANCED(token)
EMPTY_LEFT(token)
EMPTY_RIGHT(token)
TEXT()
TEXT(token)
EOT

"$MCPU_CPP" --no-config "$base/main.c" -o "$base/out"
sed '/^#/d; /^[[:space:]]*$/d; s/[[:space:]]//g' "$base/out" > "$base/norm"

cat > "$base/expected" <<'EOT'
[]
[]
[yes]
call("zero")
call("two",123,7)
""
"123"
"123y"
"Xz"
pre
pre123
post
123post
RESCANNED
(a,(b,c))
x
y
"__VA_OPT__(notsyntax)"
"__VA_OPT__(notsyntax)"ok
EOT

diff -u "$base/expected" "$base/norm"

# __VA_OPT__ remains visible in macro dumps as part of the replacement list.
"$MCPU_CPP" --no-config -dM "$base/main.c" > "$base/dump"
grep -Fx '#define HAS(...) __VA_OPT__(yes)' "$base/dump" >/dev/null
grep -Fx '#define COMMA(format,...) call(format __VA_OPT__(,) __VA_ARGS__)' "$base/dump" >/dev/null
grep -Fx '#define STR(...) #__VA_OPT__(__VA_ARGS__)' "$base/dump" >/dev/null

# __VA_OPT__ is structural syntax, not a general identifier-like extension.
cat > "$base/nonvariadic.c" <<'EOT'
#define BAD(x) __VA_OPT__(x)
EOT
if "$MCPU_CPP" --no-config "$base/nonvariadic.c" -o "$base/nonvariadic.out" 2>"$base/nonvariadic.err"; then
  echo '__VA_OPT__ unexpectedly accepted in a non-variadic macro' >&2
  exit 1
fi
grep "'__VA_OPT__' may appear only in a variadic macro replacement list" "$base/nonvariadic.err" >/dev/null

cat > "$base/object.c" <<'EOT'
#define BAD __VA_OPT__(x)
EOT
if "$MCPU_CPP" --no-config "$base/object.c" -o "$base/object.out" 2>"$base/object.err"; then
  echo '__VA_OPT__ unexpectedly accepted in an object-like macro' >&2
  exit 1
fi
grep "'__VA_OPT__' may appear only in a variadic macro replacement list" "$base/object.err" >/dev/null

cat > "$base/nested.c" <<'EOT'
#define BAD(...) __VA_OPT__(a __VA_OPT__(b))
EOT
if "$MCPU_CPP" --no-config "$base/nested.c" -o "$base/nested.out" 2>"$base/nested.err"; then
  echo 'nested __VA_OPT__ unexpectedly accepted' >&2
  exit 1
fi
grep "'__VA_OPT__' may not appear inside another '__VA_OPT__'" "$base/nested.err" >/dev/null

cat > "$base/no-open.c" <<'EOT'
#define BAD(...) __VA_OPT__ x
EOT
if "$MCPU_CPP" --no-config "$base/no-open.c" -o "$base/no-open.out" 2>"$base/no-open.err"; then
  echo '__VA_OPT__ without opening parenthesis unexpectedly accepted' >&2
  exit 1
fi
grep "'__VA_OPT__' must be followed by '('" "$base/no-open.err" >/dev/null

cat > "$base/unterminated.c" <<'EOT'
#define BAD(...) __VA_OPT__((x)
EOT
if "$MCPU_CPP" --no-config "$base/unterminated.c" -o "$base/unterminated.out" 2>"$base/unterminated.err"; then
  echo 'unterminated __VA_OPT__ unexpectedly accepted' >&2
  exit 1
fi
grep "unterminated '__VA_OPT__'" "$base/unterminated.err" >/dev/null

cat > "$base/paste-first.c" <<'EOT'
#define BAD(...) __VA_OPT__(## x)
EOT
if "$MCPU_CPP" --no-config "$base/paste-first.c" -o "$base/paste-first.out" 2>"$base/paste-first.err"; then
  echo 'leading ## inside __VA_OPT__ unexpectedly accepted' >&2
  exit 1
fi
grep "'##' cannot appear at the beginning of '__VA_OPT__'" "$base/paste-first.err" >/dev/null

cat > "$base/paste-last.c" <<'EOT'
#define BAD(...) __VA_OPT__(x ##)
EOT
if "$MCPU_CPP" --no-config "$base/paste-last.c" -o "$base/paste-last.out" 2>"$base/paste-last.err"; then
  echo 'trailing ## inside __VA_OPT__ unexpectedly accepted' >&2
  exit 1
fi
grep "'##' cannot appear at the end of '__VA_OPT__'" "$base/paste-last.err" >/dev/null

# The historical GNU comma-swallow extension remains deliberately absent.
# __VA_OPT__ is the supported way to make a separator conditional.
cat > "$base/no-gnu-comma.c" <<'EOT'
#define OLD(format, ...) call(format, ## __VA_ARGS__)
OLD("x")
EOT
"$MCPU_CPP" --no-config "$base/no-gnu-comma.c" -o "$base/no-gnu-comma.out" 2>"$base/no-gnu-comma.err"
sed '/^#/d; /^[[:space:]]*$/d; s/[[:space:]]//g' "$base/no-gnu-comma.out" > "$base/no-gnu-comma.norm"
grep -Fx 'call("x",)' "$base/no-gnu-comma.norm" >/dev/null