Add hook into frontend for sizeof() folding.

	Before, code like:

		const f = {
			var buf: byte[sizeof(int)]
		}

	would crash us, because `sizeof` would not get folded.

	A slightly subtle point: muse doens't install a hook here,
	but since it's already handling processed usefiles, the
	array sizes should already be prefolded for its viewing
	pleasure.

4 files changed, 11 insertions, 0 deletions

diff --git a/6/main.c b/6/main.c
index 7ce7d5f..ab93660 100644
--- a/6/main.c
+++ b/6/main.c
@@ -202,6 +202,7 @@ main(int argc, char **argv)
 
 	optinit(&ctx, "cd:?hSo:I:9G:O:", argv, argc);
 	asmsyntax = Defaultasm;
+	sizefn = size;
 	while (!optdone(&ctx)) {
 		switch (optnext(&ctx)) {
 		case 'O':
diff --git a/parse/fold.c b/parse/fold.c
index d01ff6a..c13b41c 100644
--- a/parse/fold.c
+++ b/parse/fold.c
@@ -13,6 +13,8 @@
 #include "util.h"
 #include "parse.h"
 
+size_t (*sizefn)(Node *n);
+
 static int
 getintlit(Node *n, vlong *v)
 {
@@ -250,6 +252,10 @@ fold(Node *n, int foldvar)
 	case Ocast:
 		r = foldcast(n);
 		break;
+	case Osize:
+		if (sizefn)
+			r = val(n->loc, sizefn(n->expr.args[0]), exprtype(n));
+		break;
 	default:
 		break;
 	}
diff --git a/parse/infer.c b/parse/infer.c
index fc9b86b..d1465ee 100644
--- a/parse/infer.c
+++ b/parse/infer.c
@@ -2031,6 +2031,9 @@ tyfix(Node *ctx, Type *orig, int noerr)
 		t->fixed = 1;
 		if (t->type == Tyarray) {
 			typesub(t->asize, noerr);
+			t->asize = fold(t->asize, 1);
+			if (exprop(t->asize) != Olit)
+				fatal(t->asize, "nonconstant array size near %s\n", ctxstr(t->asize));
 		} else if (t->type == Tystruct) {
 			inaggr++;
 			for (i = 0; i < t->nmemb; i++)
diff --git a/parse/parse.h b/parse/parse.h
index 97198a8..74abae4 100644
--- a/parse/parse.h
+++ b/parse/parse.h
@@ -573,5 +573,6 @@ extern char *objdir;
 extern char **incpaths;
 extern size_t nincpaths;
 extern char *localincpath;
+extern size_t (*sizefn)(Node *n);
 
 void yyerror(const char *s);