From bad98e94caf37db71f8114bdb8562a7caa4fb256 Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Mon, 16 Mar 2020 02:09:59 -0700
Subject: pp: Add support for macro definition and expansion

The token pasting operator `##` still needs to be implemented.
---
 cc.h                                    |   9 +
 main.c                                  |   1 +
 pp.c                                    | 499 ++++++++++++++++++++++++++++++--
 scan.c                                  |   1 +
 test/preprocess-macro-function-paren.c  |   4 +
 test/preprocess-macro-function-paren.pp |   2 +
 test/preprocess-macro-function.c        |   2 +
 test/preprocess-macro-function.pp       |   1 +
 test/preprocess-macro-hide.c            |   2 +
 test/preprocess-macro-hide.pp           |   1 +
 test/preprocess-macro-object.c          |   2 +
 test/preprocess-macro-object.pp         |   1 +
 test/preprocess-macro-stringize.c       |   2 +
 test/preprocess-macro-stringize.pp      |   1 +
 test/preprocess-standard-example-1.c    |   4 +
 test/preprocess-standard-example-1.pp   |   1 +
 test/preprocess-standard-example-2.c    |  20 ++
 test/preprocess-standard-example-2.pp   |   4 +
 test/preprocess-undef.c                 |   3 +
 test/preprocess-undef.pp                |   1 +
 token.c                                 |   2 +
 util.c                                  |  10 +
 util.h                                  |   1 +
 23 files changed, 551 insertions(+), 23 deletions(-)
 create mode 100644 test/preprocess-macro-function-paren.c
 create mode 100644 test/preprocess-macro-function-paren.pp
 create mode 100644 test/preprocess-macro-function.c
 create mode 100644 test/preprocess-macro-function.pp
 create mode 100644 test/preprocess-macro-hide.c
 create mode 100644 test/preprocess-macro-hide.pp
 create mode 100644 test/preprocess-macro-object.c
 create mode 100644 test/preprocess-macro-object.pp
 create mode 100644 test/preprocess-macro-stringize.c
 create mode 100644 test/preprocess-macro-stringize.pp
 create mode 100644 test/preprocess-standard-example-1.c
 create mode 100644 test/preprocess-standard-example-1.pp
 create mode 100644 test/preprocess-standard-example-2.c
 create mode 100644 test/preprocess-standard-example-2.pp
 create mode 100644 test/preprocess-undef.c
 create mode 100644 test/preprocess-undef.pp

diff --git a/cc.h b/cc.h
index d938ade..85f739a 100644
--- a/cc.h
+++ b/cc.h
@@ -121,6 +121,8 @@ struct location {
 
 struct token {
 	enum tokenkind kind;
+	/* whether or not the token is ineligible for expansion */
+	_Bool hide;
 	/* whether or not the token was preceeded by a space */
 	_Bool space;
 	struct location loc;
@@ -384,6 +386,13 @@ void scan(struct token *);
 
 /* preprocessor */
 
+enum ppflags {
+	/* preserve newlines in preprocessor output */
+	PPNEWLINE   = 1 << 0,
+};
+
+extern enum ppflags ppflags;
+
 void ppinit(void);
 
 void next(void);
diff --git a/main.c b/main.c
index a147c28..004df85 100644
--- a/main.c
+++ b/main.c
@@ -50,6 +50,7 @@ main(int argc, char *argv[])
 
 	ppinit();
 	if (pponly) {
+		ppflags |= PPNEWLINE;
 		while (tok.kind != TEOF) {
 			tokenprint(&tok);
 			next();
diff --git a/pp.c b/pp.c
index 4831cd6..87cb810 100644
--- a/pp.c
+++ b/pp.c
@@ -1,3 +1,4 @@
+#include <assert.h>
 #include <stdarg.h>
 #include <stdbool.h>
 #include <stdint.h>
@@ -7,14 +8,468 @@
 #include "util.h"
 #include "cc.h"
 
-static struct token pending;
+struct macroparam {
+	char *name;
+	/* whether or not the argument needs to be stringized */
+	bool stringize;
+};
+
+struct macroarg {
+	struct token *token;
+	size_t ntoken;
+	/* stringized argument */
+	struct token str;
+};
+
+struct macro {
+	enum {
+		MACROOBJ,
+		MACROFUNC,
+	} kind;
+	char *name;
+	/* whether or not this macro is ineligible for expansion */
+	bool hide;
+	/* parameters of function-like macro */
+	struct macroparam *param;
+	size_t nparam;
+	/* argument tokens of macro invocation */
+	struct macroarg *arg;
+	/* replacement list */
+	struct token *token;
+	size_t ntoken;
+};
+
+struct frame {
+	struct token *token;
+	size_t ntoken;
+	struct macro *macro;
+};
+
+enum ppflags ppflags;
+
+static struct array ctx;
+static struct map *macros;
+/* number of macros currently undergoing expansion */
+static size_t macrodepth;
 
 void
 ppinit(void)
 {
+	macros = mkmap(64);
 	next();
 }
 
+/* check if two macro definitions are equal, as in C11 6.10.3p2 */
+static bool
+macroequal(struct macro *m1, struct macro *m2)
+{
+	struct token *t1, *t2;
+	size_t i;
+
+	if (m1->kind != m2->kind)
+		return false;
+	if (m1->kind == MACROFUNC) {
+		if (m1->nparam != m2->nparam)
+			return false;
+		for (i = 0; i < m1->nparam; ++i) {
+			if (strcmp(m1->param[i].name, m2->param[i].name) != 0)
+				return false;
+		}
+	}
+	if (m1->ntoken != m2->ntoken)
+		return false;
+	for (t1 = m1->token, t2 = m2->token; t1 < m1->token + m1->ntoken; ++t1, ++t2) {
+		if (t1->kind != t2->kind)
+			return false;
+		if (t1->lit && strcmp(t1->lit, t2->lit) != 0)
+			return false;
+	}
+	return true;
+}
+
+/* find the index of a macro parameter with the given name */
+static size_t
+macroparam(struct macro *m, const char *name)
+{
+	size_t i;
+
+	for (i = 0; i < m->nparam; ++i) {
+		if (strcmp(m->param[i].name, name) == 0)
+			return i;
+	}
+	return -1;
+}
+
+/* lookup a macro by name */
+static struct macro *
+macroget(char *name)
+{
+	struct mapkey k;
+
+	mapkey(&k, name, strlen(name));
+	return mapget(macros, &k);
+}
+
+static void
+macrodone(struct macro *m)
+{
+	m->hide = false;
+	if (m->kind == MACROFUNC && m->nparam > 0) {
+		free(m->arg[0].token);
+		free(m->arg);
+	}
+	--macrodepth;
+}
+
+static struct token *
+framenext(struct frame *f)
+{
+	return f->ntoken--, f->token++;
+}
+
+/* push a new context frame */
+static struct frame *
+ctxpush(struct token *t, size_t n, struct macro *m)
+{
+	struct frame *f;
+
+	f = arrayadd(&ctx, sizeof(*f));
+	f->token = t;
+	f->ntoken = n;
+	f->macro = m;
+	return f;
+}
+
+/* get the next frame with tokens left */
+static struct frame *
+ctxframe(void)
+{
+	struct frame *f;
+
+	for (f = arraylast(&ctx, sizeof(*f)); ctx.len; --f, ctx.len -= sizeof(*f)) {
+		if (f->ntoken)
+			return f;
+		if (f->macro)
+			macrodone(f->macro);
+	}
+	return NULL;
+}
+
+/* get the next token from the context */
+static struct token *
+ctxnext(void)
+{
+	struct frame *f;
+	struct token *t;
+	struct macro *m;
+	size_t i;
+
+again:
+	f = ctxframe();
+	if (!f)
+		return NULL;
+	m = f->macro;
+	if (m && m->kind == MACROFUNC) {
+		/* try to expand macro parameter */
+		switch (f->token->kind) {
+		case THASH:
+			framenext(f);
+			t = framenext(f);
+			assert(t && t->kind == TIDENT);
+			i = macroparam(m, t->lit);
+			assert(i != -1);
+			f = ctxpush(&m->arg[i].str, 1, NULL);
+			break;
+		case TIDENT:
+			i = macroparam(m, f->token->lit);
+			if (i == -1)
+				break;
+			framenext(f);
+			if (m->arg[i].ntoken == 0)
+				goto again;
+			f = ctxpush(m->arg[i].token, m->arg[i].ntoken, NULL);
+			break;
+		}
+		/* XXX: token concatenation */
+	}
+	return framenext(f);
+}
+
+static void
+define(void)
+{
+	struct token *t;
+	struct macro *m;
+	struct macroparam *p;
+	struct array params = {0}, repl = {0};
+	struct mapkey k;
+	void **entry;
+	bool stringize;
+	size_t i;
+
+	if (tok.kind != TIDENT)
+		error(&tok.loc, "expected identifier after #define");
+	m = xmalloc(sizeof(*m));
+	m->name = tok.lit;
+	m->hide = false;
+	t = arrayadd(&repl, sizeof(*t));
+	scan(t);
+	if (t->kind == TLPAREN && !t->space) {
+		m->kind = MACROFUNC;
+		/* read macro parameter names */
+		while (scan(&tok), tok.kind == TIDENT) {
+			p = arrayadd(&params, sizeof(*p));
+			p->name = tok.lit;
+			p->stringize = false;
+			if (scan(&tok), tok.kind != TCOMMA)
+				break;
+		}
+		if (tok.kind != TRPAREN)
+			error(&tok.loc, "expected ')' after macro parameter list");
+		scan(t);  /* first token in replacement list */
+	} else {
+		m->kind = MACROOBJ;
+	}
+
+	/* read macro body */
+	m->param = params.val;
+	m->nparam = params.len / sizeof(m->param[0]);
+	t->space = false;
+	while (t->kind != TNEWLINE) {
+		if (t->kind == THASHHASH)
+			error(&t->loc, "'##' operator is not yet implemented");
+		stringize = t->kind == THASH;
+		t = arrayadd(&repl, sizeof(*t));
+		scan(t);
+		if (stringize && m->kind == MACROFUNC) {
+			if (t->kind != TIDENT)
+				error(&t->loc, "expected macro parameter name after '#' operator");
+			i = macroparam(m, t->lit);
+			if (i == -1)
+				error(&t->loc, "'%s' is not a macro parameter name", t->lit);
+			m->param[i].stringize = true;
+		}
+	}
+	m->token = repl.val;
+	m->ntoken = repl.len / sizeof(*t) - 1;
+	tok = *t;
+
+	mapkey(&k, m->name, strlen(m->name));
+	entry = mapput(macros, &k);
+	if (*entry && !macroequal(m, *entry))
+		error(&tok.loc, "redefinition of macro '%s'", m->name);
+	*entry = m;
+}
+
+static void
+undef(void)
+{
+	char *name;
+	struct mapkey k;
+	void **entry;
+	struct macro *m;
+
+	name = tokencheck(&tok, TIDENT, "after #undef");
+	mapkey(&k, name, strlen(name));
+	entry = mapput(macros, &k);
+	m = *entry;
+	if (m) {
+		free(name);
+		free(m->param);
+		free(m->token);
+		*entry = NULL;
+	}
+	scan(&tok);
+}
+
+static void
+directive(void)
+{
+	enum ppflags oldflags;
+	char *name;
+
+	scan(&tok);
+	if (tok.kind == TNEWLINE)
+		return;  /* empty directive */
+	oldflags = ppflags;
+	ppflags |= PPNEWLINE;
+	name = tokencheck(&tok, TIDENT, "or newline after '#'");
+	if (strcmp(name, "if") == 0) {
+		error(&tok.loc, "#if directive is not implemented");
+	} else if (strcmp(name, "ifdef") == 0) {
+		error(&tok.loc, "#ifdef directive is not implemented");
+	} else if (strcmp(name, "ifndef") == 0) {
+		error(&tok.loc, "#ifndef directive is not implemented");
+	} else if (strcmp(name, "elif") == 0) {
+		error(&tok.loc, "#elif directive is not implemented");
+	} else if (strcmp(name, "endif") == 0) {
+		error(&tok.loc, "#endif directive is not implemented");
+	} else if (strcmp(name, "include") == 0) {
+		error(&tok.loc, "#include directive is not implemented");
+	} else if (strcmp(name, "define") == 0) {
+		scan(&tok);
+		define();
+	} else if (strcmp(name, "undef") == 0) {
+		scan(&tok);
+		undef();
+	} else if (strcmp(name, "line") == 0) {
+		error(&tok.loc, "#line directive is not implemented");
+	} else if (strcmp(name, "error") == 0) {
+		error(&tok.loc, "#error directive is not implemented");
+	} else if (strcmp(name, "pragma") == 0) {
+		error(&tok.loc, "#pragma directive is not implemented");
+	} else {
+		error(&tok.loc, "invalid preprocessor directive #%s", name);
+	}
+	free(name);
+	tokencheck(&tok, TNEWLINE, "after preprocessing directive");
+	ppflags = oldflags;
+}
+
+/* get the next token without expanding it */
+static void
+nextinto(struct token *t)
+{
+	static bool newline = true;
+
+	for (;;) {
+		scan(t);
+		if (newline && t->kind == THASH) {
+			directive();
+		} else {
+			newline = tok.kind == TNEWLINE;
+			break;
+		}
+	}
+}
+
+static struct token *
+rawnext(void)
+{
+	struct token *t;
+
+	t = ctxnext();
+	if (!t) {
+		t = &tok;
+		nextinto(t);
+	}
+	return t;
+}
+
+static bool
+peekparen(void)
+{
+	static struct array pending;
+	struct token *t;
+	struct frame *f;
+
+	t = ctxnext();
+	if (t) {
+		if (t->kind == TLPAREN)
+			return true;
+		f = arraylast(&ctx, sizeof(*f));
+		--f->token;
+		++f->ntoken;
+		return false;
+	}
+	pending.len = 0;
+	do t = arrayadd(&pending, sizeof(*t)), nextinto(t);
+	while (t->kind == TNEWLINE);
+	if (t->kind == TLPAREN)
+		return true;
+	ctxpush(pending.val, pending.len / sizeof(*t), NULL);
+	return false;
+}
+
+static void
+stringize(struct array *buf, struct token *t)
+{
+	const char *lit;
+
+	lit = t->lit ? t->lit : tokstr[t->kind];
+	/* XXX: double escape string literal */
+	arrayaddbuf(buf, lit, strlen(lit));
+}
+
+static bool
+expand(struct token *t)
+{
+	struct macro *m;
+	struct macroarg *arg;
+	struct array str, tok;
+	size_t i, depth, paren;
+
+	if (t->kind != TIDENT)
+		return false;
+	m = macroget(t->lit);
+	if (!m || m->hide || t->hide) {
+		t->hide = true;
+		return false;
+	}
+	if (m->kind == MACROFUNC) {
+		if (!peekparen())
+			return false;
+		/* read macro arguments */
+		paren = 0;
+		depth = macrodepth;
+		tok = (struct array){0};
+		if (m->nparam > 0) {
+			arg = xreallocarray(NULL, m->nparam, sizeof(*arg));
+		} else {
+			arg = NULL;
+			t = rawnext();
+		}
+		for (i = 0; i < m->nparam && t->kind != TRPAREN; ++i) {
+			if (m->param[i].stringize) {
+				str = (struct array){0};
+				arrayaddbuf(&str, "\"", 1);
+			}
+			arg[i].ntoken = 0;
+			for (;;) {
+				t = rawnext();
+				if (t->kind == TEOF)
+					error(&t->loc, "EOF when reading macro parameters");
+				if (macrodepth <= depth) {
+					/* adjust current macro depth, in case it got shallower */
+					depth = macrodepth;
+					if (paren == 0 && (t->kind == TCOMMA || t->kind == TRPAREN))
+						break;
+					switch (t->kind) {
+					case TLPAREN: ++paren; break;
+					case TRPAREN: --paren; break;
+					}
+					if (m->param[i].stringize)
+						stringize(&str, t);
+				}
+				if (!expand(t)) {
+					arrayaddbuf(&tok, t, sizeof(*t));
+					++arg[i].ntoken;
+				}
+			}
+			if (m->param[i].stringize) {
+				arrayaddbuf(&str, "\"", 2);
+				arg[i].str = (struct token){
+					.kind = TSTRINGLIT,
+					.lit = str.val,
+				};
+			}
+		}
+		if (i < m->nparam)
+			error(&t->loc, "not enough arguments for macro '%s'", m->name);
+		tokencheck(t, TRPAREN, "after macro arguments");
+		t = tok.val;
+		for (i = 0; i < m->nparam; ++i) {
+			arg[i].token = t;
+			t += arg[i].ntoken;
+		}
+		m->arg = arg;
+	}
+	ctxpush(m->token, m->ntoken, m);
+	m->hide = true;
+	++macrodepth;
+	return true;
+}
+
 static void
 keyword(struct token *tok)
 {
@@ -98,36 +553,34 @@ keyword(struct token *tok)
 	}
 }
 
-static void
-nextinto(struct token *t)
-{
-	do scan(t);
-	while (t->kind == TNEWLINE);
-	if (t->kind == TIDENT)
-		keyword(t);
-}
-
 void
 next(void)
 {
-	if (pending.kind) {
-		tok = pending;
-		pending.kind = TNONE;
-	} else {
-		nextinto(&tok);
-	}
+	struct token *t;
+
+	do t = rawnext();
+	while (expand(t) || t->kind == TNEWLINE && !(ppflags & PPNEWLINE));
+	tok = *t;
+	if (tok.kind == TIDENT)
+		keyword(&tok);
 }
 
 bool
 peek(int kind)
 {
-	if (!pending.kind)
-		nextinto(&pending);
-	if (pending.kind != kind)
-		return false;
-	pending.kind = TNONE;
-	nextinto(&tok);
-	return true;
+	static struct token pending;
+	struct token old;
+
+	old = tok;
+	next();
+	if (tok.kind == kind) {
+		next();
+		return true;
+	}
+	pending = tok;
+	tok = old;
+	ctxpush(&pending, 1, NULL);
+	return false;
 }
 
 char *
diff --git a/scan.c b/scan.c
index 557b595..c9eb5ea 100644
--- a/scan.c
+++ b/scan.c
@@ -472,4 +472,5 @@ scan(struct token *t)
 		t->lit = NULL;
 	}
 	t->space = scanner->sawspace;
+	t->hide = false;
 }
diff --git a/test/preprocess-macro-function-paren.c b/test/preprocess-macro-function-paren.c
new file mode 100644
index 0000000..c7c7639
--- /dev/null
+++ b/test/preprocess-macro-function-paren.c
@@ -0,0 +1,4 @@
+#define g(x) [x]
+#define f(a) g a (def)
+f((abc))
+f()
diff --git a/test/preprocess-macro-function-paren.pp b/test/preprocess-macro-function-paren.pp
new file mode 100644
index 0000000..6d86709
--- /dev/null
+++ b/test/preprocess-macro-function-paren.pp
@@ -0,0 +1,2 @@
+[abc] (def)
+[def]
diff --git a/test/preprocess-macro-function.c b/test/preprocess-macro-function.c
new file mode 100644
index 0000000..87b4c07
--- /dev/null
+++ b/test/preprocess-macro-function.c
@@ -0,0 +1,2 @@
+#define f(a, b) a, abc, b
+f(foo, bar)
diff --git a/test/preprocess-macro-function.pp b/test/preprocess-macro-function.pp
new file mode 100644
index 0000000..c8109cd
--- /dev/null
+++ b/test/preprocess-macro-function.pp
@@ -0,0 +1 @@
+foo, abc, bar
diff --git a/test/preprocess-macro-hide.c b/test/preprocess-macro-hide.c
new file mode 100644
index 0000000..22671c7
--- /dev/null
+++ b/test/preprocess-macro-hide.c
@@ -0,0 +1,2 @@
+#define foo foo bar
+foo
diff --git a/test/preprocess-macro-hide.pp b/test/preprocess-macro-hide.pp
new file mode 100644
index 0000000..d675fa4
--- /dev/null
+++ b/test/preprocess-macro-hide.pp
@@ -0,0 +1 @@
+foo bar
diff --git a/test/preprocess-macro-object.c b/test/preprocess-macro-object.c
new file mode 100644
index 0000000..f4c8b21
--- /dev/null
+++ b/test/preprocess-macro-object.c
@@ -0,0 +1,2 @@
+#define foo bar
+foo
diff --git a/test/preprocess-macro-object.pp b/test/preprocess-macro-object.pp
new file mode 100644
index 0000000..5716ca5
--- /dev/null
+++ b/test/preprocess-macro-object.pp
@@ -0,0 +1 @@
+bar
diff --git a/test/preprocess-macro-stringize.c b/test/preprocess-macro-stringize.c
new file mode 100644
index 0000000..528c88e
--- /dev/null
+++ b/test/preprocess-macro-stringize.c
@@ -0,0 +1,2 @@
+#define stringize(a) #a
+stringize(hello)
diff --git a/test/preprocess-macro-stringize.pp b/test/preprocess-macro-stringize.pp
new file mode 100644
index 0000000..3580093
--- /dev/null
+++ b/test/preprocess-macro-stringize.pp
@@ -0,0 +1 @@
+"hello"
diff --git a/test/preprocess-standard-example-1.c b/test/preprocess-standard-example-1.c
new file mode 100644
index 0000000..84447e0
--- /dev/null
+++ b/test/preprocess-standard-example-1.c
@@ -0,0 +1,4 @@
+/* C11 6.10.3.4p4 */
+#define f(a) a*g
+#define g(a) f(a)
+f(2)(9)
diff --git a/test/preprocess-standard-example-1.pp b/test/preprocess-standard-example-1.pp
new file mode 100644
index 0000000..738d396
--- /dev/null
+++ b/test/preprocess-standard-example-1.pp
@@ -0,0 +1 @@
+2*9*g
diff --git a/test/preprocess-standard-example-2.c b/test/preprocess-standard-example-2.c
new file mode 100644
index 0000000..0deb2ad
--- /dev/null
+++ b/test/preprocess-standard-example-2.c
@@ -0,0 +1,20 @@
+/* C11 6.10.3.5p5 with token concatenation disabled for now */
+#define    x          3
+#define    f(a)       f(x * (a))
+#undef     x
+#define    x          2
+#define    g          f
+#define    z          z[0]
+#define    h          g(~
+#define    m(a)       a(w)
+#define    w          0,1
+#define    t(a)       a
+#define    p()        int
+#define    q(x)       x
+//#define    r(x,y)     x ## y
+#define    str(x)     # x
+f(y+1) + f(f(z)) % t(t(g)(0) + t)(1);
+g(x+(3,4)-w) | h 5) & m
+	(f)^m(m);
+p() i[q()] = { q(1), /*r(2,3), r(4,), r(,5), r(,)*/ };
+char c[2][6] = { str(hello), str() };
diff --git a/test/preprocess-standard-example-2.pp b/test/preprocess-standard-example-2.pp
new file mode 100644
index 0000000..3a52eb0
--- /dev/null
+++ b/test/preprocess-standard-example-2.pp
@@ -0,0 +1,4 @@
+f(2 * (y+1)) +f(2 * (f(2 * (z[0])))) %f(2 * (0)) + t(1);
+f(2 * (2+(3,4)-0,1)) |f(2 * (~ 5)) &f(2 * (0,1))^m(0,1);
+int i[] = {1, };
+char c[2][6] = {"hello","" };
diff --git a/test/preprocess-undef.c b/test/preprocess-undef.c
new file mode 100644
index 0000000..c43f9ea
--- /dev/null
+++ b/test/preprocess-undef.c
@@ -0,0 +1,3 @@
+#define foo bar
+#undef foo
+foo
diff --git a/test/preprocess-undef.pp b/test/preprocess-undef.pp
new file mode 100644
index 0000000..257cc56
--- /dev/null
+++ b/test/preprocess-undef.pp
@@ -0,0 +1 @@
+foo
diff --git a/token.c b/token.c
index 6d4484d..dc2df02 100644
--- a/token.c
+++ b/token.c
@@ -116,6 +116,8 @@ tokenprint(const struct token *t)
 {
 	const char *str;
 
+	if (t->space)
+		fputc(' ', stdout);
 	switch (t->kind) {
 	case TIDENT:
 	case TNUMBER:
diff --git a/util.c b/util.c
index 1229f2c..63511a3 100644
--- a/util.c
+++ b/util.c
@@ -1,3 +1,4 @@
+#include <assert.h>
 #include <errno.h>
 #include <stdarg.h>
 #include <stdint.h>
@@ -116,6 +117,15 @@ arrayaddbuf(struct array *a, const void *src, size_t n)
 	memcpy(arrayadd(a, n), src, n);
 }
 
+void *
+arraylast(struct array *a, size_t n)
+{
+	if (a->len == 0)
+		return NULL;
+	assert(n <= a->len);
+	return (char *)a->val + a->len - n;
+}
+
 void
 listinsert(struct list *list, struct list *new)
 {
diff --git a/util.h b/util.h
index 504662b..0081667 100644
--- a/util.h
+++ b/util.h
@@ -42,6 +42,7 @@ void listremove(struct list *);
 void *arrayadd(struct array *, size_t);
 void arrayaddptr(struct array *, void *);
 void arrayaddbuf(struct array *, const void *, size_t);
+void *arraylast(struct array *, size_t);
 #define arrayforeach(a, m) for (m = (a)->val; m != (void *)((char *)(a)->val + (a)->len); ++m)
 
 /* map */
-- 
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