wcc: c-side mangles private decls; main exempt as entry-point convention

cmd/wcc/lex.c

@@ -94,6 +94,27 @@ skipws(Lex *l)
 			continue;
 		}
 		if (c == '/' && lpeek(l, 1) == '/') {
+			lget(l); lget(l);	/* consume '//' */
+			/* `// MODULE: foo` directive emitted by the ww
+			 * driver before each source-file's section in
+			 * combined.ww. Captured so cgen can mangle
+			 * non-exported symbols by module. */
+			if (lpeek(l, 0) == ' '
+			    && lpeek(l, 1) == 'M' && lpeek(l, 2) == 'O'
+			    && lpeek(l, 3) == 'D' && lpeek(l, 4) == 'U'
+			    && lpeek(l, 5) == 'L' && lpeek(l, 6) == 'E'
+			    && lpeek(l, 7) == ':' && lpeek(l, 8) == ' ') {
+				for (int i = 0; i < 9; i++) lget(l);
+				u64 start = l->pos;
+				while ((c = lpeek(l, 0)) >= 0
+				    && c != '\n' && c != '\r')
+					lget(l);
+				u64 n = l->pos - start;
+				char *m = amalloc(l->a, n + 1);
+				memcpy(m, l->src + start, n);
+				m[n] = '\0';
+				l->module = m;
+			}
 			while ((c = lpeek(l, 0)) >= 0 && c != '\n')
 				lget(l);
 			continue;

cmd/wcc/parse.c

@@ -1174,6 +1174,10 @@ parsefile(Parser *p)
 			advance(p);
 			continue;
 		}
+		/* Stamp the lex's current `// MODULE: foo` directive on the
+		 * decl. cgen uses it to mangle non-exported names so two
+		 * modules can each privately define `cstrlen`/`streq`/etc. */
+		if (d != NULL) d->module = p->l->module;
 		if (head == NULL) head = d;
 		else tail->next = d;
 		tail = d;

cmd/wcc/ww.h

@@ -196,6 +196,7 @@ struct Lex {
 	i32	col;
 	Arena	*a;		/* token-text arena */
 	int	errs;
+	const char *module;	/* current `// MODULE: foo` directive, or NULL */
 };
 
 void	lexinit(Lex*, Arena*, const char *file, const char *src, u64 len);
@@ -303,6 +304,11 @@ struct Node {
 	int		export;
 	Type		*type;	/* filled in by checker */
 	const char	*tsuffix;	/* typed numeric literal suffix */
+	const char	*module;	/* `// MODULE: foo` directive at the
+					 * decl's section in combined.ww.
+					 * NULL for nested nodes; only top-
+					 * level decls (fn/def/type/let)
+					 * carry it. */
 };
 
 Node	*newnode(Arena*, Nkind, Pos);