diff --git a/internal/cgen/base/io-private.h b/internal/cgen/base/io-private.h
index 340144a..fad529b 100644
--- a/internal/cgen/base/io-private.h
+++ b/internal/cgen/base/io-private.h
@@ -17,7 +17,9 @@
 // ---------------- I/O
 
 // "Null" as in "/dev/null", not as in "nullptr".
-static wuffs_base__io_buffer wuffs_base__global__null_io_buffer = {};
+//
+// TODO: ensure that this is zero-initialized.
+static wuffs_base__io_buffer wuffs_base__global__null_io_buffer;
 
 static inline wuffs_base__io_buffer*  //
 wuffs_base__null_io_reader() {
diff --git a/internal/cgen/data.go b/internal/cgen/data.go
index db3659e..09121da 100644
--- a/internal/cgen/data.go
+++ b/internal/cgen/data.go
@@ -163,13 +163,13 @@
 	""
 
 const baseIOPrivateH = "" +
-	"// ---------------- I/O\n\n// \"Null\" as in \"/dev/null\", not as in \"nullptr\".\nstatic wuffs_base__io_buffer wuffs_base__global__null_io_buffer = {};\n\nstatic inline wuffs_base__io_buffer*  //\nwuffs_base__null_io_reader() {\n  return &wuffs_base__global__null_io_buffer;\n}\n\nstatic inline wuffs_base__io_buffer*  //\nwuffs_base__null_io_writer() {\n  return &wuffs_base__global__null_io_buffer;\n}\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_n_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_n_from_history Wuffs method should also take an unroll hint argument,\n  // and the cgen can look if that argument is the constant expression '3'.\n  //\n  // See also wuffs_base__io_writer__copy_n_from_history_fast below.\n  //\n  // Alternatively, or additionally, have a sloppy_copy_n_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_n_from_history_fast is like the\n// wuffs_base__io_writer__copy_n_from_history function above, but has stronger\n// 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_n_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_n_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)(io" +
-	"2_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_n_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\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->m" +
-	"eta.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\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" +
+	"// ---------------- I/O\n\n// \"Null\" as in \"/dev/null\", not as in \"nullptr\".\n//\n// TODO: ensure that this is zero-initialized.\nstatic wuffs_base__io_buffer wuffs_base__global__null_io_buffer;\n\nstatic inline wuffs_base__io_buffer*  //\nwuffs_base__null_io_reader() {\n  return &wuffs_base__global__null_io_buffer;\n}\n\nstatic inline wuffs_base__io_buffer*  //\nwuffs_base__null_io_writer() {\n  return &wuffs_base__global__null_io_buffer;\n}\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_n_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_n_from_history Wuffs method should also take an unroll hint argument,\n  // and the cgen can look if that argument is the constant expression '3'.\n  //\n  // See also wuffs_base__io_writer__copy_n_from_history_fast below.\n  //\n  // Alternatively, or additionally, have a sloppy_copy_n_from_history method\n  // that copies 8 bytes at a time, poss" +
+	"ibly 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_n_from_history_fast is like the\n// wuffs_base__io_writer__copy_n_from_history function above, but has stronger\n// 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_n_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_n_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 > ((s" +
+	"ize_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_n_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\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_ba" +
+	"se__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\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 = dat" +
+	"a.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__null_io_reader wuffs_base__null_io_reader\n#define wuffs_base__utility__null_io_writer wuffs_base__null_io_writer\n" +
 	""
diff --git a/release/c/wuffs-unsupported-snapshot.c b/release/c/wuffs-unsupported-snapshot.c
index ebe1154..964d7dd 100644
--- a/release/c/wuffs-unsupported-snapshot.c
+++ b/release/c/wuffs-unsupported-snapshot.c
@@ -4457,7 +4457,9 @@
 // ---------------- I/O
 
 // "Null" as in "/dev/null", not as in "nullptr".
-static wuffs_base__io_buffer wuffs_base__global__null_io_buffer = {};
+//
+// TODO: ensure that this is zero-initialized.
+static wuffs_base__io_buffer wuffs_base__global__null_io_buffer;
 
 static inline wuffs_base__io_buffer*  //
 wuffs_base__null_io_reader() {