diff --git a/selfhost/cmd/w6a/asm.ww b/selfhost/cmd/w6a/asm.ww
index cf933042..218a5512 100644
--- a/selfhost/cmd/w6a/asm.ww
+++ b/selfhost/cmd/w6a/asm.ww
@@ -23,10 +23,10 @@ export fn emitbyte(a: *asm_, b: u8) void = {
 		let nc: u64 = a.textcap;
 		if (nc == 0u64) { nc = 4096u64; };
 		nc = nc * 2u64;
-		let nb: *u8 = rt.malloc(nc): *u8;
+		let nb: []u8 = alloc([], nc)!;
 		let i: u64 = 0u64;
 		for (i < a.textlen) { nb[i] = a.text[i]; i += 1u64; };
-		a.text = nb;
+		a.text = nb.ptr;
 		a.textcap = nc;
 	};
 	a.text[a.textlen] = b;
@@ -60,10 +60,10 @@ export fn emitdatabyte(a: *asm_, b: u8) void = {
 		let nc: u64 = a.datacap;
 		if (nc == 0u64) { nc = 256u64; };
 		nc = nc * 2u64;
-		let nb: *u8 = rt.malloc(nc): *u8;
+		let nb: []u8 = alloc([], nc)!;
 		let i: u64 = 0u64;
 		for (i < a.datalen) { nb[i] = a.data[i]; i += 1u64; };
-		a.data = nb;
+		a.data = nb.ptr;
 		a.datacap = nc;
 	};
 	a.data[a.datalen] = b;
diff --git a/selfhost/cmd/w6a/main.combined.ww b/selfhost/cmd/w6a/main.combined.ww
index 1fc9a699..045d7844 100644
--- a/selfhost/cmd/w6a/main.combined.ww
+++ b/selfhost/cmd/w6a/main.combined.ww
@@ -1760,10 +1760,10 @@ export fn emitbyte(a: *asm_, b: u8) void = {
 		let nc: u64 = a.textcap;
 		if (nc == 0u64) { nc = 4096u64; };
 		nc = nc * 2u64;
-		let nb: *u8 = rt.malloc(nc): *u8;
+		let nb: []u8 = alloc([], nc)!;
 		let i: u64 = 0u64;
 		for (i < a.textlen) { nb[i] = a.text[i]; i += 1u64; };
-		a.text = nb;
+		a.text = nb.ptr;
 		a.textcap = nc;
 	};
 	a.text[a.textlen] = b;
@@ -1797,10 +1797,10 @@ export fn emitdatabyte(a: *asm_, b: u8) void = {
 		let nc: u64 = a.datacap;
 		if (nc == 0u64) { nc = 256u64; };
 		nc = nc * 2u64;
-		let nb: *u8 = rt.malloc(nc): *u8;
+		let nb: []u8 = alloc([], nc)!;
 		let i: u64 = 0u64;
 		for (i < a.datalen) { nb[i] = a.data[i]; i += 1u64; };
-		a.data = nb;
+		a.data = nb.ptr;
 		a.datacap = nc;
 	};
 	a.data[a.datalen] = b;
@@ -2687,17 +2687,18 @@ fn bufinit(b: *buf, a: *arena) void = {
 	b.a = a;
 	b.cap = 256u64;
 	b.n = 0u64;
-	b.p = amalloc(a, b.cap): *u8;
+	let np: []u8 = alloc([], b.cap)!;
+	b.p = np.ptr;
 };
 
 fn bufgrow(b: *buf, need: u64) void = {
 	if (b.n + need <= b.cap) { return; };
 	let nc: u64 = b.cap;
 	for (nc < b.n + need) { nc = nc * 2u64; };
-	let np: *u8 = amalloc(b.a, nc): *u8;
+	let np: []u8 = alloc([], nc)!;
 	let i: u64 = 0u64;
 	for (i < b.n) { np[i] = b.p[i]; i += 1u64; };
-	b.p = np;
+	b.p = np.ptr;
 	b.cap = nc;
 };
 
diff --git a/selfhost/cmd/w6a/obj.ww b/selfhost/cmd/w6a/obj.ww
index 8c28077c..6683b192 100644
--- a/selfhost/cmd/w6a/obj.ww
+++ b/selfhost/cmd/w6a/obj.ww
@@ -97,17 +97,18 @@ fn bufinit(b: *buf, a: *arena) void = {
 	b.a = a;
 	b.cap = 256u64;
 	b.n = 0u64;
-	b.p = amalloc(a, b.cap): *u8;
+	let np: []u8 = alloc([], b.cap)!;
+	b.p = np.ptr;
 };
 
 fn bufgrow(b: *buf, need: u64) void = {
 	if (b.n + need <= b.cap) { return; };
 	let nc: u64 = b.cap;
 	for (nc < b.n + need) { nc = nc * 2u64; };
-	let np: *u8 = amalloc(b.a, nc): *u8;
+	let np: []u8 = alloc([], nc)!;
 	let i: u64 = 0u64;
 	for (i < b.n) { np[i] = b.p[i]; i += 1u64; };
-	b.p = np;
+	b.p = np.ptr;
 	b.cap = nc;
 };
 
diff --git a/selfhost/cmd/w6l/main.combined.ww b/selfhost/cmd/w6l/main.combined.ww
index 190a8d47..7ef734a7 100644
--- a/selfhost/cmd/w6l/main.combined.ww
+++ b/selfhost/cmd/w6l/main.combined.ww
@@ -1084,13 +1084,13 @@ fn emittext(l: *lnk, src: *u8, n: u64) void = {
 		// Grow by mmap'ing a fresh region and copying. The old buffer
 		// is leaked into the page allocator; for a linker run this is
 		// trivial waste.
-		let nb: *u8 = rt.malloc(nc): *u8;
+		let nb: []u8 = alloc([], nc)!;
 		let i: u64 = 0u64;
 		for (i < l.textlen) {
 			nb[i] = l.text[i];
 			i += 1u64;
 		};
-		l.text = nb;
+		l.text = nb.ptr;
 		l.textcap = nc;
 	};
 	let i: u64 = 0u64;
@@ -1106,13 +1106,13 @@ fn emitdata(l: *lnk, src: *u8, n: u64) void = {
 		let nc: u64 = l.datacap;
 		if (nc == 0u64) { nc = 256u64; };
 		for (nc < l.datalen + n) { nc = nc * 2u64; };
-		let nb: *u8 = rt.malloc(nc): *u8;
+		let nb: []u8 = alloc([], nc)!;
 		let i: u64 = 0u64;
 		for (i < l.datalen) {
 			nb[i] = l.data[i];
 			i += 1u64;
 		};
-		l.data = nb;
+		l.data = nb.ptr;
 		l.datacap = nc;
 	};
 	let i: u64 = 0u64;
diff --git a/selfhost/cmd/w6l/obj.ww b/selfhost/cmd/w6l/obj.ww
index 53358183..c559ee69 100644
--- a/selfhost/cmd/w6l/obj.ww
+++ b/selfhost/cmd/w6l/obj.ww
@@ -110,13 +110,13 @@ fn emittext(l: *lnk, src: *u8, n: u64) void = {
 		// Grow by mmap'ing a fresh region and copying. The old buffer
 		// is leaked into the page allocator; for a linker run this is
 		// trivial waste.
-		let nb: *u8 = rt.malloc(nc): *u8;
+		let nb: []u8 = alloc([], nc)!;
 		let i: u64 = 0u64;
 		for (i < l.textlen) {
 			nb[i] = l.text[i];
 			i += 1u64;
 		};
-		l.text = nb;
+		l.text = nb.ptr;
 		l.textcap = nc;
 	};
 	let i: u64 = 0u64;
@@ -132,13 +132,13 @@ fn emitdata(l: *lnk, src: *u8, n: u64) void = {
 		let nc: u64 = l.datacap;
 		if (nc == 0u64) { nc = 256u64; };
 		for (nc < l.datalen + n) { nc = nc * 2u64; };
-		let nb: *u8 = rt.malloc(nc): *u8;
+		let nb: []u8 = alloc([], nc)!;
 		let i: u64 = 0u64;
 		for (i < l.datalen) {
 			nb[i] = l.data[i];
 			i += 1u64;
 		};
-		l.data = nb;
+		l.data = nb.ptr;
 		l.datacap = nc;
 	};
 	let i: u64 = 0u64;