diff --git a/internal/cgen/base/io-private.h b/internal/cgen/base/io-private.h
index db61e88..e4fd9ce 100644
--- a/internal/cgen/base/io-private.h
+++ b/internal/cgen/base/io-private.h
@@ -106,14 +106,14 @@
 wuffs_base__io_writer__copy_n32_from_reader(uint8_t** ptr_iop_w,
                                             uint8_t* io2_w,
                                             uint32_t length,
-                                            uint8_t** ptr_iop_r,
-                                            uint8_t* io2_r) {
+                                            const uint8_t** ptr_iop_r,
+                                            const uint8_t* io2_r) {
   uint8_t* iop_w = *ptr_iop_w;
   size_t n = length;
   if (n > ((size_t)(io2_w - iop_w))) {
     n = (size_t)(io2_w - iop_w);
   }
-  uint8_t* iop_r = *ptr_iop_r;
+  const uint8_t* iop_r = *ptr_iop_r;
   if (n > ((size_t)(io2_r - iop_r))) {
     n = (size_t)(io2_r - iop_r);
   }
@@ -176,8 +176,8 @@
 //  - 1 means inconclusive, equivalent to "$short read".
 //  - 2 means failure.
 static inline uint32_t  //
-wuffs_base__io_reader__match7(uint8_t* iop_r,
-                              uint8_t* io2_r,
+wuffs_base__io_reader__match7(const uint8_t* iop_r,
+                              const uint8_t* io2_r,
                               wuffs_base__io_buffer* r,
                               uint64_t a) {
   uint32_t n = a & 7;
@@ -201,10 +201,10 @@
 
 static inline wuffs_base__io_buffer*  //
 wuffs_base__io_reader__set(wuffs_base__io_buffer* b,
-                           uint8_t** ptr_iop_r,
-                           uint8_t** ptr_io0_r,
-                           uint8_t** ptr_io1_r,
-                           uint8_t** ptr_io2_r,
+                           const uint8_t** ptr_iop_r,
+                           const uint8_t** ptr_io0_r,
+                           const uint8_t** ptr_io1_r,
+                           const uint8_t** ptr_io2_r,
                            wuffs_base__slice_u8 data) {
   b->data = data;
   b->meta.wi = data.len;
@@ -220,15 +220,24 @@
   return b;
 }
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wcast-qual"
+// TODO: can we avoid the const_cast (by deleting this function)? This might
+// involve converting the call sites to take an io_reader instead of a slice u8
+// (the result of io_reader.take).
 static inline wuffs_base__slice_u8  //
-wuffs_base__io_reader__take(uint8_t** ptr_iop_r, uint8_t* io2_r, uint64_t n) {
+wuffs_base__io_reader__take(const uint8_t** ptr_iop_r,
+                            const uint8_t* io2_r,
+                            uint64_t n) {
   if (n <= ((size_t)(io2_r - *ptr_iop_r))) {
-    uint8_t* p = *ptr_iop_r;
+    const uint8_t* p = *ptr_iop_r;
     *ptr_iop_r += n;
-    return wuffs_base__make_slice_u8(p, n);
+    // The arg is what C calls C++'s "const_cast<uint8_t*>(p)".
+    return wuffs_base__make_slice_u8((uint8_t*)(p), n);
   }
   return wuffs_base__make_slice_u8(NULL, 0);
 }
+#pragma GCC diagnostic pop
 
 static inline wuffs_base__io_buffer*  //
 wuffs_base__io_writer__set(wuffs_base__io_buffer* b,
diff --git a/internal/cgen/data.go b/internal/cgen/data.go
index abdef5f..dc46046 100644
--- a/internal/cgen/data.go
+++ b/internal/cgen/data.go
@@ -327,11 +327,12 @@
 const baseIOPrivateH = "" +
 	"// ---------------- I/O\n\nstatic inline uint64_t  //\nwuffs_base__io__count_since(uint64_t mark, uint64_t index) {\n  if (index >= mark) {\n    return index - mark;\n  }\n  return 0;\n}\n\nstatic inline wuffs_base__slice_u8  //\nwuffs_base__io__since(uint64_t mark, uint64_t index, uint8_t* ptr) {\n  if (index >= mark) {\n    return wuffs_base__make_slice_u8(ptr + mark, index - mark);\n  }\n  return wuffs_base__make_slice_u8(NULL, 0);\n}\n\nstatic inline uint32_t  //\nwuffs_base__io_writer__copy_n32_from_history(uint8_t** ptr_iop_w,\n                                             uint8_t* io1_w,\n                                             uint8_t* io2_w,\n                                             uint32_t length,\n                                             uint32_t distance) {\n  if (!distance) {\n    return 0;\n  }\n  uint8_t* p = *ptr_iop_w;\n  if ((size_t)(p - io1_w) < (size_t)(distance)) {\n    return 0;\n  }\n  uint8_t* q = p - distance;\n  size_t n = (size_t)(io2_w - p);\n  if ((size_t)(length) > n) {\n    length = (uint32_t)(n);\n " +
 	" } else {\n    n = (size_t)(length);\n  }\n  // TODO: unrolling by 3 seems best for the std/deflate benchmarks, but that\n  // is mostly because 3 is the minimum length for the deflate format. This\n  // function implementation shouldn't overfit to that one format. Perhaps the\n  // copy_n32_from_history Wuffs method should also take an unroll hint\n  // argument, and the cgen can look if that argument is the constant\n  // expression '3'.\n  //\n  // See also wuffs_base__io_writer__copy_n32_from_history_fast below.\n  //\n  // Alternatively, or additionally, have a sloppy_copy_n32_from_history method\n  // that copies 8 bytes at a time, possibly writing more than length bytes?\n  for (; n >= 3; n -= 3) {\n    *p++ = *q++;\n    *p++ = *q++;\n    *p++ = *q++;\n  }\n  for (; n; n--) {\n    *p++ = *q++;\n  }\n  *ptr_iop_w = p;\n  return length;\n}\n\n// wuffs_base__io_writer__copy_n32_from_history_fast is like the\n// wuffs_base__io_writer__copy_n32_from_history function above, but has\n// stronger pre-conditions. The caller needs to prove" +
-	" that:\n//  - distance >  0\n//  - distance <= (*ptr_iop_w - io1_w)\n//  - length   <= (io2_w      - *ptr_iop_w)\nstatic inline uint32_t  //\nwuffs_base__io_writer__copy_n32_from_history_fast(uint8_t** ptr_iop_w,\n                                                  uint8_t* io1_w,\n                                                  uint8_t* io2_w,\n                                                  uint32_t length,\n                                                  uint32_t distance) {\n  uint8_t* p = *ptr_iop_w;\n  uint8_t* q = p - distance;\n  uint32_t n = length;\n  for (; n >= 3; n -= 3) {\n    *p++ = *q++;\n    *p++ = *q++;\n    *p++ = *q++;\n  }\n  for (; n; n--) {\n    *p++ = *q++;\n  }\n  *ptr_iop_w = p;\n  return length;\n}\n\nstatic inline uint32_t  //\nwuffs_base__io_writer__copy_n32_from_reader(uint8_t** ptr_iop_w,\n                                            uint8_t* io2_w,\n                                            uint32_t length,\n                                            uint8_t** ptr_iop_r,\n                             " +
-	"               uint8_t* io2_r) {\n  uint8_t* iop_w = *ptr_iop_w;\n  size_t n = length;\n  if (n > ((size_t)(io2_w - iop_w))) {\n    n = (size_t)(io2_w - iop_w);\n  }\n  uint8_t* iop_r = *ptr_iop_r;\n  if (n > ((size_t)(io2_r - iop_r))) {\n    n = (size_t)(io2_r - iop_r);\n  }\n  if (n > 0) {\n    memmove(iop_w, iop_r, n);\n    *ptr_iop_w += n;\n    *ptr_iop_r += n;\n  }\n  return (uint32_t)(n);\n}\n\nstatic inline uint64_t  //\nwuffs_base__io_writer__copy_from_slice(uint8_t** ptr_iop_w,\n                                       uint8_t* io2_w,\n                                       wuffs_base__slice_u8 src) {\n  uint8_t* iop_w = *ptr_iop_w;\n  size_t n = src.len;\n  if (n > ((size_t)(io2_w - iop_w))) {\n    n = (size_t)(io2_w - iop_w);\n  }\n  if (n > 0) {\n    memmove(iop_w, src.ptr, n);\n    *ptr_iop_w += n;\n  }\n  return (uint64_t)(n);\n}\n\nstatic inline uint32_t  //\nwuffs_base__io_writer__copy_n32_from_slice(uint8_t** ptr_iop_w,\n                                           uint8_t* io2_w,\n                                           uint32_t" +
-	" length,\n                                           wuffs_base__slice_u8 src) {\n  uint8_t* iop_w = *ptr_iop_w;\n  size_t n = src.len;\n  if (n > length) {\n    n = length;\n  }\n  if (n > ((size_t)(io2_w - iop_w))) {\n    n = (size_t)(io2_w - iop_w);\n  }\n  if (n > 0) {\n    memmove(iop_w, src.ptr, n);\n    *ptr_iop_w += n;\n  }\n  return (uint32_t)(n);\n}\n\n// wuffs_base__io_reader__match7 returns whether the io_reader's upcoming bytes\n// start with the given prefix (up to 7 bytes long). It is peek-like, not\n// read-like, in that there are no side-effects.\n//\n// The low 3 bits of a hold the prefix length, n.\n//\n// The high 56 bits of a hold the prefix itself, in little-endian order. The\n// first prefix byte is in bits 8..=15, the second prefix byte is in bits\n// 16..=23, etc. The high (8 * (7 - n)) bits are ignored.\n//\n// There are three possible return values:\n//  - 0 means success.\n//  - 1 means inconclusive, equivalent to \"$short read\".\n//  - 2 means failure.\nstatic inline uint32_t  //\nwuffs_base__io_reader__match7(ui" +
-	"nt8_t* iop_r,\n                              uint8_t* io2_r,\n                              wuffs_base__io_buffer* r,\n                              uint64_t a) {\n  uint32_t n = a & 7;\n  a >>= 8;\n  if ((io2_r - iop_r) >= 8) {\n    uint64_t x = wuffs_base__load_u64le__no_bounds_check(iop_r);\n    uint32_t shift = 8 * (8 - n);\n    return ((a << shift) == (x << shift)) ? 0 : 2;\n  }\n  for (; n > 0; n--) {\n    if (iop_r >= io2_r) {\n      return (r && r->meta.closed) ? 2 : 1;\n    } else if (*iop_r != ((uint8_t)(a))) {\n      return 2;\n    }\n    iop_r++;\n    a >>= 8;\n  }\n  return 0;\n}\n\nstatic inline wuffs_base__io_buffer*  //\nwuffs_base__io_reader__set(wuffs_base__io_buffer* b,\n                           uint8_t** ptr_iop_r,\n                           uint8_t** ptr_io0_r,\n                           uint8_t** ptr_io1_r,\n                           uint8_t** ptr_io2_r,\n                           wuffs_base__slice_u8 data) {\n  b->data = data;\n  b->meta.wi = data.len;\n  b->meta.ri = 0;\n  b->meta.pos = 0;\n  b->meta.closed = fal" +
-	"se;\n\n  *ptr_iop_r = data.ptr;\n  *ptr_io0_r = data.ptr;\n  *ptr_io1_r = data.ptr;\n  *ptr_io2_r = data.ptr + data.len;\n\n  return b;\n}\n\nstatic inline wuffs_base__slice_u8  //\nwuffs_base__io_reader__take(uint8_t** ptr_iop_r, uint8_t* io2_r, uint64_t n) {\n  if (n <= ((size_t)(io2_r - *ptr_iop_r))) {\n    uint8_t* p = *ptr_iop_r;\n    *ptr_iop_r += n;\n    return wuffs_base__make_slice_u8(p, n);\n  }\n  return wuffs_base__make_slice_u8(NULL, 0);\n}\n\nstatic inline wuffs_base__io_buffer*  //\nwuffs_base__io_writer__set(wuffs_base__io_buffer* b,\n                           uint8_t** ptr_iop_w,\n                           uint8_t** ptr_io0_w,\n                           uint8_t** ptr_io1_w,\n                           uint8_t** ptr_io2_w,\n                           wuffs_base__slice_u8 data) {\n  b->data = data;\n  b->meta.wi = 0;\n  b->meta.ri = 0;\n  b->meta.pos = 0;\n  b->meta.closed = false;\n\n  *ptr_iop_w = data.ptr;\n  *ptr_io0_w = data.ptr;\n  *ptr_io1_w = data.ptr;\n  *ptr_io2_w = data.ptr + data.len;\n\n  return b;\n}\n\n  " +
+	" that:\n//  - distance >  0\n//  - distance <= (*ptr_iop_w - io1_w)\n//  - length   <= (io2_w      - *ptr_iop_w)\nstatic inline uint32_t  //\nwuffs_base__io_writer__copy_n32_from_history_fast(uint8_t** ptr_iop_w,\n                                                  uint8_t* io1_w,\n                                                  uint8_t* io2_w,\n                                                  uint32_t length,\n                                                  uint32_t distance) {\n  uint8_t* p = *ptr_iop_w;\n  uint8_t* q = p - distance;\n  uint32_t n = length;\n  for (; n >= 3; n -= 3) {\n    *p++ = *q++;\n    *p++ = *q++;\n    *p++ = *q++;\n  }\n  for (; n; n--) {\n    *p++ = *q++;\n  }\n  *ptr_iop_w = p;\n  return length;\n}\n\nstatic inline uint32_t  //\nwuffs_base__io_writer__copy_n32_from_reader(uint8_t** ptr_iop_w,\n                                            uint8_t* io2_w,\n                                            uint32_t length,\n                                            const uint8_t** ptr_iop_r,\n                       " +
+	"                     const uint8_t* io2_r) {\n  uint8_t* iop_w = *ptr_iop_w;\n  size_t n = length;\n  if (n > ((size_t)(io2_w - iop_w))) {\n    n = (size_t)(io2_w - iop_w);\n  }\n  const uint8_t* iop_r = *ptr_iop_r;\n  if (n > ((size_t)(io2_r - iop_r))) {\n    n = (size_t)(io2_r - iop_r);\n  }\n  if (n > 0) {\n    memmove(iop_w, iop_r, n);\n    *ptr_iop_w += n;\n    *ptr_iop_r += n;\n  }\n  return (uint32_t)(n);\n}\n\nstatic inline uint64_t  //\nwuffs_base__io_writer__copy_from_slice(uint8_t** ptr_iop_w,\n                                       uint8_t* io2_w,\n                                       wuffs_base__slice_u8 src) {\n  uint8_t* iop_w = *ptr_iop_w;\n  size_t n = src.len;\n  if (n > ((size_t)(io2_w - iop_w))) {\n    n = (size_t)(io2_w - iop_w);\n  }\n  if (n > 0) {\n    memmove(iop_w, src.ptr, n);\n    *ptr_iop_w += n;\n  }\n  return (uint64_t)(n);\n}\n\nstatic inline uint32_t  //\nwuffs_base__io_writer__copy_n32_from_slice(uint8_t** ptr_iop_w,\n                                           uint8_t* io2_w,\n                                 " +
+	"          uint32_t length,\n                                           wuffs_base__slice_u8 src) {\n  uint8_t* iop_w = *ptr_iop_w;\n  size_t n = src.len;\n  if (n > length) {\n    n = length;\n  }\n  if (n > ((size_t)(io2_w - iop_w))) {\n    n = (size_t)(io2_w - iop_w);\n  }\n  if (n > 0) {\n    memmove(iop_w, src.ptr, n);\n    *ptr_iop_w += n;\n  }\n  return (uint32_t)(n);\n}\n\n// wuffs_base__io_reader__match7 returns whether the io_reader's upcoming bytes\n// start with the given prefix (up to 7 bytes long). It is peek-like, not\n// read-like, in that there are no side-effects.\n//\n// The low 3 bits of a hold the prefix length, n.\n//\n// The high 56 bits of a hold the prefix itself, in little-endian order. The\n// first prefix byte is in bits 8..=15, the second prefix byte is in bits\n// 16..=23, etc. The high (8 * (7 - n)) bits are ignored.\n//\n// There are three possible return values:\n//  - 0 means success.\n//  - 1 means inconclusive, equivalent to \"$short read\".\n//  - 2 means failure.\nstatic inline uint32_t  //\nwuffs_base__io" +
+	"_reader__match7(const uint8_t* iop_r,\n                              const uint8_t* io2_r,\n                              wuffs_base__io_buffer* r,\n                              uint64_t a) {\n  uint32_t n = a & 7;\n  a >>= 8;\n  if ((io2_r - iop_r) >= 8) {\n    uint64_t x = wuffs_base__load_u64le__no_bounds_check(iop_r);\n    uint32_t shift = 8 * (8 - n);\n    return ((a << shift) == (x << shift)) ? 0 : 2;\n  }\n  for (; n > 0; n--) {\n    if (iop_r >= io2_r) {\n      return (r && r->meta.closed) ? 2 : 1;\n    } else if (*iop_r != ((uint8_t)(a))) {\n      return 2;\n    }\n    iop_r++;\n    a >>= 8;\n  }\n  return 0;\n}\n\nstatic inline wuffs_base__io_buffer*  //\nwuffs_base__io_reader__set(wuffs_base__io_buffer* b,\n                           const uint8_t** ptr_iop_r,\n                           const uint8_t** ptr_io0_r,\n                           const uint8_t** ptr_io1_r,\n                           const uint8_t** ptr_io2_r,\n                           wuffs_base__slice_u8 data) {\n  b->data = data;\n  b->meta.wi = data.len;\n  b->" +
+	"meta.ri = 0;\n  b->meta.pos = 0;\n  b->meta.closed = false;\n\n  *ptr_iop_r = data.ptr;\n  *ptr_io0_r = data.ptr;\n  *ptr_io1_r = data.ptr;\n  *ptr_io2_r = data.ptr + data.len;\n\n  return b;\n}\n\n#pragma GCC diagnostic push\n#pragma GCC diagnostic ignored \"-Wcast-qual\"\n// TODO: can we avoid the const_cast (by deleting this function)? This might\n// involve converting the call sites to take an io_reader instead of a slice u8\n// (the result of io_reader.take).\nstatic inline wuffs_base__slice_u8  //\nwuffs_base__io_reader__take(const uint8_t** ptr_iop_r,\n                            const uint8_t* io2_r,\n                            uint64_t n) {\n  if (n <= ((size_t)(io2_r - *ptr_iop_r))) {\n    const uint8_t* p = *ptr_iop_r;\n    *ptr_iop_r += n;\n    // The arg is what C calls C++'s \"const_cast<uint8_t*>(p)\".\n    return wuffs_base__make_slice_u8((uint8_t*)(p), n);\n  }\n  return wuffs_base__make_slice_u8(NULL, 0);\n}\n#pragma GCC diagnostic pop\n\nstatic inline wuffs_base__io_buffer*  //\nwuffs_base__io_writer__set(wuffs_base__io_buff" +
+	"er* b,\n                           uint8_t** ptr_iop_w,\n                           uint8_t** ptr_io0_w,\n                           uint8_t** ptr_io1_w,\n                           uint8_t** ptr_io2_w,\n                           wuffs_base__slice_u8 data) {\n  b->data = data;\n  b->meta.wi = 0;\n  b->meta.ri = 0;\n  b->meta.pos = 0;\n  b->meta.closed = false;\n\n  *ptr_iop_w = data.ptr;\n  *ptr_io0_w = data.ptr;\n  *ptr_io1_w = data.ptr;\n  *ptr_io2_w = data.ptr + data.len;\n\n  return b;\n}\n\n  " +
 	"" +
 	"// ---------------- I/O (Utility)\n\n#define wuffs_base__utility__empty_io_reader wuffs_base__empty_io_reader\n#define wuffs_base__utility__empty_io_writer wuffs_base__empty_io_writer\n" +
 	""
diff --git a/internal/cgen/statement.go b/internal/cgen/statement.go
index fd19ad3..b4e17fb 100644
--- a/internal/cgen/statement.go
+++ b/internal/cgen/statement.go
@@ -262,9 +262,9 @@
 		if e.Operator() != 0 {
 			prefix = aPrefix
 		}
-		cTyp := "reader"
+		cTyp, qualifier := "reader", "const "
 		if e.MType().QID()[1] == t.IDIOWriter {
-			cTyp = "writer"
+			cTyp, qualifier = "writer", ""
 		}
 		name := e.Ident().Str(g.tm)
 		b.printf("wuffs_base__io_buffer* %s%d_%s%s = %s%s;\n",
@@ -274,14 +274,14 @@
 		// does this work if the io_bind body advances these pointers, either
 		// directly or by calling other funcs?
 		if e.Operator() == 0 {
-			b.printf("uint8_t *%s%d_%s%s%s = %s%s%s;\n",
-				oPrefix, ioBindNum, iopPrefix, prefix, name, iopPrefix, prefix, name)
-			b.printf("uint8_t *%s%d_%s%s%s = %s%s%s;\n",
-				oPrefix, ioBindNum, io0Prefix, prefix, name, io0Prefix, prefix, name)
-			b.printf("uint8_t *%s%d_%s%s%s = %s%s%s;\n",
-				oPrefix, ioBindNum, io1Prefix, prefix, name, io1Prefix, prefix, name)
-			b.printf("uint8_t *%s%d_%s%s%s = %s%s%s;\n",
-				oPrefix, ioBindNum, io2Prefix, prefix, name, io2Prefix, prefix, name)
+			b.printf("%suint8_t *%s%d_%s%s%s = %s%s%s;\n",
+				qualifier, oPrefix, ioBindNum, iopPrefix, prefix, name, iopPrefix, prefix, name)
+			b.printf("%suint8_t *%s%d_%s%s%s = %s%s%s;\n",
+				qualifier, oPrefix, ioBindNum, io0Prefix, prefix, name, io0Prefix, prefix, name)
+			b.printf("%suint8_t *%s%d_%s%s%s = %s%s%s;\n",
+				qualifier, oPrefix, ioBindNum, io1Prefix, prefix, name, io1Prefix, prefix, name)
+			b.printf("%suint8_t *%s%d_%s%s%s = %s%s%s;\n",
+				qualifier, oPrefix, ioBindNum, io2Prefix, prefix, name, io2Prefix, prefix, name)
 		}
 
 		if n.Keyword() == t.IDIOBind {
diff --git a/internal/cgen/var.go b/internal/cgen/var.go
index 4828f52..9c3e3d7 100644
--- a/internal/cgen/var.go
+++ b/internal/cgen/var.go
@@ -86,9 +86,17 @@
 
 	elem := ""
 	if typ.IsIOType() {
-		elem = "uint8_t"
+		if typ.QID()[1] == t.IDIOReader {
+			elem = "const uint8_t"
+		} else {
+			elem = "uint8_t"
+		}
 	} else if typ.IsTokenType() {
-		elem = "wuffs_base__token"
+		if typ.QID()[1] == t.IDTokenReader {
+			elem = "const wuffs_base__token"
+		} else {
+			elem = "wuffs_base__token"
+		}
 	} else {
 		return nil
 	}
@@ -303,10 +311,18 @@
 		}
 
 		if typ.IsIOType() {
-			b.printf("uint8_t* %s%s%s WUFFS_BASE__POTENTIALLY_UNUSED = NULL;\n", iopPrefix, vPrefix, name)
-			b.printf("uint8_t* %s%s%s WUFFS_BASE__POTENTIALLY_UNUSED = NULL;\n", io0Prefix, vPrefix, name)
-			b.printf("uint8_t* %s%s%s WUFFS_BASE__POTENTIALLY_UNUSED = NULL;\n", io1Prefix, vPrefix, name)
-			b.printf("uint8_t* %s%s%s WUFFS_BASE__POTENTIALLY_UNUSED = NULL;\n", io2Prefix, vPrefix, name)
+			qualifier := ""
+			if typ.QID()[1] == t.IDIOReader {
+				qualifier = "const "
+			}
+			b.printf("%suint8_t* %s%s%s WUFFS_BASE__POTENTIALLY_UNUSED = NULL;\n",
+				qualifier, iopPrefix, vPrefix, name)
+			b.printf("%suint8_t* %s%s%s WUFFS_BASE__POTENTIALLY_UNUSED = NULL;\n",
+				qualifier, io0Prefix, vPrefix, name)
+			b.printf("%suint8_t* %s%s%s WUFFS_BASE__POTENTIALLY_UNUSED = NULL;\n",
+				qualifier, io1Prefix, vPrefix, name)
+			b.printf("%suint8_t* %s%s%s WUFFS_BASE__POTENTIALLY_UNUSED = NULL;\n",
+				qualifier, io2Prefix, vPrefix, name)
 		}
 	}
 	return nil
diff --git a/release/c/wuffs-unsupported-snapshot.c b/release/c/wuffs-unsupported-snapshot.c
index 8ec9186..b5bf088 100644
--- a/release/c/wuffs-unsupported-snapshot.c
+++ b/release/c/wuffs-unsupported-snapshot.c
@@ -7713,14 +7713,14 @@
 wuffs_base__io_writer__copy_n32_from_reader(uint8_t** ptr_iop_w,
                                             uint8_t* io2_w,
                                             uint32_t length,
-                                            uint8_t** ptr_iop_r,
-                                            uint8_t* io2_r) {
+                                            const uint8_t** ptr_iop_r,
+                                            const uint8_t* io2_r) {
   uint8_t* iop_w = *ptr_iop_w;
   size_t n = length;
   if (n > ((size_t)(io2_w - iop_w))) {
     n = (size_t)(io2_w - iop_w);
   }
-  uint8_t* iop_r = *ptr_iop_r;
+  const uint8_t* iop_r = *ptr_iop_r;
   if (n > ((size_t)(io2_r - iop_r))) {
     n = (size_t)(io2_r - iop_r);
   }
@@ -7783,8 +7783,8 @@
 //  - 1 means inconclusive, equivalent to "$short read".
 //  - 2 means failure.
 static inline uint32_t  //
-wuffs_base__io_reader__match7(uint8_t* iop_r,
-                              uint8_t* io2_r,
+wuffs_base__io_reader__match7(const uint8_t* iop_r,
+                              const uint8_t* io2_r,
                               wuffs_base__io_buffer* r,
                               uint64_t a) {
   uint32_t n = a & 7;
@@ -7808,10 +7808,10 @@
 
 static inline wuffs_base__io_buffer*  //
 wuffs_base__io_reader__set(wuffs_base__io_buffer* b,
-                           uint8_t** ptr_iop_r,
-                           uint8_t** ptr_io0_r,
-                           uint8_t** ptr_io1_r,
-                           uint8_t** ptr_io2_r,
+                           const uint8_t** ptr_iop_r,
+                           const uint8_t** ptr_io0_r,
+                           const uint8_t** ptr_io1_r,
+                           const uint8_t** ptr_io2_r,
                            wuffs_base__slice_u8 data) {
   b->data = data;
   b->meta.wi = data.len;
@@ -7827,15 +7827,24 @@
   return b;
 }
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wcast-qual"
+// TODO: can we avoid the const_cast (by deleting this function)? This might
+// involve converting the call sites to take an io_reader instead of a slice u8
+// (the result of io_reader.take).
 static inline wuffs_base__slice_u8  //
-wuffs_base__io_reader__take(uint8_t** ptr_iop_r, uint8_t* io2_r, uint64_t n) {
+wuffs_base__io_reader__take(const uint8_t** ptr_iop_r,
+                            const uint8_t* io2_r,
+                            uint64_t n) {
   if (n <= ((size_t)(io2_r - *ptr_iop_r))) {
-    uint8_t* p = *ptr_iop_r;
+    const uint8_t* p = *ptr_iop_r;
     *ptr_iop_r += n;
-    return wuffs_base__make_slice_u8(p, n);
+    // The arg is what C calls C++'s "const_cast<uint8_t*>(p)".
+    return wuffs_base__make_slice_u8((uint8_t*)(p), n);
   }
   return wuffs_base__make_slice_u8(NULL, 0);
 }
+#pragma GCC diagnostic pop
 
 static inline wuffs_base__io_buffer*  //
 wuffs_base__io_writer__set(wuffs_base__io_buffer* b,
@@ -12123,10 +12132,10 @@
   uint32_t v_bits_per_pixel = 0;
   uint32_t v_compression = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -12713,10 +12722,10 @@
   self->private_impl.active_coroutine = 0;
   wuffs_base__status status = wuffs_base__make_status(NULL);
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -12837,10 +12846,10 @@
   uint64_t v_n = 0;
   wuffs_base__slice_u8 v_src = {0};
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -13111,10 +13120,10 @@
                                wuffs_base__io_buffer* a_src) {
   wuffs_base__status status = wuffs_base__make_status(NULL);
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -14840,10 +14849,10 @@
   uint32_t v_type = 0;
   wuffs_base__status v_status = wuffs_base__make_status(NULL);
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -15001,10 +15010,10 @@
       io2_a_dst = iop_a_dst;
     }
   }
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -15169,10 +15178,10 @@
   uint32_t v_rep_count = 0;
   uint32_t v_b3 = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -15725,10 +15734,10 @@
       io2_a_dst = iop_a_dst;
     }
   }
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -16028,10 +16037,10 @@
       io2_a_dst = iop_a_dst;
     }
   }
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -16689,10 +16698,10 @@
   uint16_t v_lm1_b = 0;
   uint16_t v_lm1_a = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -17523,10 +17532,10 @@
 
   uint64_t v_chunk_length = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -17777,10 +17786,10 @@
   uint32_t v_background_color = 0;
   uint8_t v_flags = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -17918,10 +17927,10 @@
   uint8_t v_flags = 0;
   uint8_t v_lw = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -18074,10 +18083,10 @@
 
   uint8_t v_block_type = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -18185,10 +18194,10 @@
   uint8_t v_c[6] = {0};
   uint32_t v_i = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -18258,10 +18267,10 @@
   uint32_t v_j = 0;
   uint32_t v_argb = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -18473,10 +18482,10 @@
 
   uint8_t v_label = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -18567,10 +18576,10 @@
 
   uint8_t v_block_size = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -18643,10 +18652,10 @@
   bool v_is_iccp = false;
   bool v_is_xmp = false;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -18884,10 +18893,10 @@
   uint8_t v_flags = 0;
   uint16_t v_gc_duration_centiseconds = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -19012,10 +19021,10 @@
                                            wuffs_base__io_buffer* a_src) {
   wuffs_base__status status = wuffs_base__make_status(NULL);
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -19348,10 +19357,10 @@
 
   uint64_t v_chunk_length = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -19606,10 +19615,10 @@
   uint32_t v_background_color = 0;
   uint8_t v_flags = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -19747,10 +19756,10 @@
   uint8_t v_flags = 0;
   uint8_t v_lw = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -19944,10 +19953,10 @@
 
   uint8_t v_block_type = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -20055,10 +20064,10 @@
   uint8_t v_c[6] = {0};
   uint32_t v_i = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -20128,10 +20137,10 @@
   uint32_t v_j = 0;
   uint32_t v_argb = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -20343,10 +20352,10 @@
 
   uint8_t v_label = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -20437,10 +20446,10 @@
 
   uint8_t v_block_size = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -20513,10 +20522,10 @@
   bool v_is_iccp = false;
   bool v_is_xmp = false;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -20754,10 +20763,10 @@
   uint8_t v_flags = 0;
   uint16_t v_gc_duration_centiseconds = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -20882,10 +20891,10 @@
                                     wuffs_base__io_buffer* a_src) {
   wuffs_base__status status = wuffs_base__make_status(NULL);
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -21067,10 +21076,10 @@
   wuffs_base__status v_status = wuffs_base__make_status(NULL);
   uint8_t v_lw = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -21268,19 +21277,19 @@
   wuffs_base__slice_u8 v_compressed = {0};
   wuffs_base__io_buffer u_r = wuffs_base__empty_io_buffer();
   wuffs_base__io_buffer* v_r = &u_r;
-  uint8_t* iop_v_r WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io0_v_r WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_v_r WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_v_r WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_v_r WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io0_v_r WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_v_r WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_v_r WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   uint64_t v_mark = 0;
   wuffs_base__status v_lzw_status = wuffs_base__make_status(NULL);
   wuffs_base__status v_copy_status = wuffs_base__make_status(NULL);
   wuffs_base__slice_u8 v_uncompressed = {0};
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -21366,10 +21375,10 @@
         }
         {
           wuffs_base__io_buffer* o_0_v_r = v_r;
-          uint8_t* o_0_iop_v_r = iop_v_r;
-          uint8_t* o_0_io0_v_r = io0_v_r;
-          uint8_t* o_0_io1_v_r = io1_v_r;
-          uint8_t* o_0_io2_v_r = io2_v_r;
+          const uint8_t* o_0_iop_v_r = iop_v_r;
+          const uint8_t* o_0_io0_v_r = io0_v_r;
+          const uint8_t* o_0_io1_v_r = io1_v_r;
+          const uint8_t* o_0_io2_v_r = io2_v_r;
           v_r = wuffs_base__io_reader__set(
               &u_r, &iop_v_r, &io0_v_r, &io1_v_r, &io2_v_r,
               wuffs_base__slice_u8__subslice_ij(
@@ -21864,10 +21873,10 @@
       io2_a_dst = iop_a_dst;
     }
   }
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -22578,10 +22587,10 @@
       io2_a_dst = iop_a_dst;
     }
   }
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -23726,10 +23735,10 @@
   uint32_t v_n = 0;
   uint32_t v_floating_point = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -23860,10 +23869,10 @@
   uint8_t v_c = 0;
   uint32_t v_n = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -23924,10 +23933,10 @@
       io2_a_dst = iop_a_dst;
     }
   }
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -24036,10 +24045,10 @@
       io2_a_dst = iop_a_dst;
     }
   }
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -24221,10 +24230,10 @@
       io2_a_dst = iop_a_dst;
     }
   }
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -24389,10 +24398,10 @@
       io2_a_dst = iop_a_dst;
     }
   }
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -24656,10 +24665,10 @@
   uint32_t v_x32 = 0;
   uint64_t v_x64 = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -24794,10 +24803,10 @@
   self->private_impl.active_coroutine = 0;
   wuffs_base__status status = wuffs_base__make_status(NULL);
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -24925,10 +24934,10 @@
   uint8_t v_src[1] = {0};
   uint8_t v_c = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -25075,10 +25084,10 @@
   uint64_t v_bytes_per_row = 0;
   uint64_t v_total_bytes = 0;
 
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;
@@ -25549,10 +25558,10 @@
       io2_a_dst = iop_a_dst;
     }
   }
-  uint8_t* iop_a_src = NULL;
-  uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
-  uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* iop_a_src = NULL;
+  const uint8_t* io0_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io1_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
+  const uint8_t* io2_a_src WUFFS_BASE__POTENTIALLY_UNUSED = NULL;
   if (a_src) {
     io0_a_src = a_src->data.ptr;
     io1_a_src = io0_a_src + a_src->meta.ri;