Have tests let the initializers memset to zero
diff --git a/test/c/std/adler32.c b/test/c/std/adler32.c
index 884a10a..9050a62 100644
--- a/test/c/std/adler32.c
+++ b/test/c/std/adler32.c
@@ -129,11 +129,11 @@
 
     int j;
     for (j = 0; j < 2; j++) {
-      wuffs_adler32__hasher checksum = ((wuffs_adler32__hasher){});
-      status = wuffs_adler32__hasher__check_wuffs_version(
-          &checksum, sizeof checksum, WUFFS_VERSION);
+      wuffs_adler32__hasher checksum;
+      status = wuffs_adler32__hasher__initialize(&checksum, sizeof checksum,
+                                                 WUFFS_VERSION, 0);
       if (status) {
-        RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+        RETURN_FAIL("initialize: \"%s\"", status);
       }
 
       uint32_t got = 0;
@@ -191,11 +191,11 @@
 
   int i;
   for (i = 0; i < 64; i++) {
-    wuffs_adler32__hasher checksum = ((wuffs_adler32__hasher){});
-    const char* status = wuffs_adler32__hasher__check_wuffs_version(
-        &checksum, sizeof checksum, WUFFS_VERSION);
+    wuffs_adler32__hasher checksum;
+    const char* status = wuffs_adler32__hasher__initialize(
+        &checksum, sizeof checksum, WUFFS_VERSION, 0);
     if (status) {
-      RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+      RETURN_FAIL("initialize: \"%s\"", status);
     }
     uint32_t got =
         wuffs_adler32__hasher__update(&checksum, ((wuffs_base__slice_u8){
@@ -222,9 +222,9 @@
   if (rlimit) {
     len = wuffs_base__u64__min(len, rlimit);
   }
-  wuffs_adler32__hasher checksum = ((wuffs_adler32__hasher){});
-  const char* status = wuffs_adler32__hasher__check_wuffs_version(
-      &checksum, sizeof checksum, WUFFS_VERSION);
+  wuffs_adler32__hasher checksum;
+  const char* status = wuffs_adler32__hasher__initialize(
+      &checksum, sizeof checksum, WUFFS_VERSION, 0);
   if (status) {
     return status;
   }
diff --git a/test/c/std/crc32.c b/test/c/std/crc32.c
index 118de3b..8cfd4a3 100644
--- a/test/c/std/crc32.c
+++ b/test/c/std/crc32.c
@@ -129,11 +129,11 @@
 
     int j;
     for (j = 0; j < 2; j++) {
-      wuffs_crc32__ieee_hasher checksum = ((wuffs_crc32__ieee_hasher){});
-      status = wuffs_crc32__ieee_hasher__check_wuffs_version(
-          &checksum, sizeof checksum, WUFFS_VERSION);
+      wuffs_crc32__ieee_hasher checksum;
+      status = wuffs_crc32__ieee_hasher__initialize(&checksum, sizeof checksum,
+                                                    WUFFS_VERSION, 0);
       if (status) {
-        RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+        RETURN_FAIL("initialize: \"%s\"", status);
       }
 
       uint32_t got = 0;
@@ -212,11 +212,11 @@
       got ^= 0xFFFFFFFF;
 
     } else {
-      wuffs_crc32__ieee_hasher checksum = ((wuffs_crc32__ieee_hasher){});
-      const char* status = wuffs_crc32__ieee_hasher__check_wuffs_version(
-          &checksum, sizeof checksum, WUFFS_VERSION);
+      wuffs_crc32__ieee_hasher checksum;
+      const char* status = wuffs_crc32__ieee_hasher__initialize(
+          &checksum, sizeof checksum, WUFFS_VERSION, 0);
       if (status) {
-        RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+        RETURN_FAIL("initialize: \"%s\"", status);
       }
       got = wuffs_crc32__ieee_hasher__update(&checksum, data);
     }
@@ -257,9 +257,9 @@
   if (rlimit) {
     len = wuffs_base__u64__min(len, rlimit);
   }
-  wuffs_crc32__ieee_hasher checksum = ((wuffs_crc32__ieee_hasher){});
-  const char* status = wuffs_crc32__ieee_hasher__check_wuffs_version(
-      &checksum, sizeof checksum, WUFFS_VERSION);
+  wuffs_crc32__ieee_hasher checksum;
+  const char* status = wuffs_crc32__ieee_hasher__initialize(
+      &checksum, sizeof checksum, WUFFS_VERSION, 0);
   if (status) {
     return status;
   }
diff --git a/test/c/std/deflate.c b/test/c/std/deflate.c
index f064dea..e68542a 100644
--- a/test/c/std/deflate.c
+++ b/test/c/std/deflate.c
@@ -139,11 +139,11 @@
                                  wuffs_base__io_buffer* src,
                                  uint64_t wlimit,
                                  uint64_t rlimit) {
-  wuffs_deflate__decoder dec = ((wuffs_deflate__decoder){});
-  const char* status = wuffs_deflate__decoder__check_wuffs_version(
-      &dec, sizeof dec, WUFFS_VERSION);
+  wuffs_deflate__decoder dec;
+  const char* status =
+      wuffs_deflate__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
 
   while (true) {
@@ -266,11 +266,11 @@
     }
     got.meta.wi = 0;
 
-    wuffs_deflate__decoder dec = ((wuffs_deflate__decoder){});
-    status = wuffs_deflate__decoder__check_wuffs_version(&dec, sizeof dec,
-                                                         WUFFS_VERSION);
+    wuffs_deflate__decoder dec;
+    status =
+        wuffs_deflate__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
     if (status) {
-      RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+      RETURN_FAIL("initialize: \"%s\"", status);
     }
 
     src.meta.closed = false;
@@ -361,11 +361,11 @@
   const int full_history_size = 0x8000;
   int i;
   for (i = -2; i <= +2; i++) {
-    wuffs_deflate__decoder dec = ((wuffs_deflate__decoder){});
-    status = wuffs_deflate__decoder__check_wuffs_version(&dec, sizeof dec,
-                                                         WUFFS_VERSION);
+    wuffs_deflate__decoder dec;
+    status =
+        wuffs_deflate__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
     if (status) {
-      RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+      RETURN_FAIL("initialize: \"%s\"", status);
     }
 
     status = do_test_wuffs_deflate_history(
@@ -439,11 +439,11 @@
     const char* fragment = "3.14";
     const uint32_t fragment_length = 4;
 
-    wuffs_deflate__decoder dec = ((wuffs_deflate__decoder){});
-    status = wuffs_deflate__decoder__check_wuffs_version(&dec, sizeof dec,
-                                                         WUFFS_VERSION);
+    wuffs_deflate__decoder dec;
+    status =
+        wuffs_deflate__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
     if (status) {
-      RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+      RETURN_FAIL("initialize: \"%s\"", status);
     }
 
     status = do_test_wuffs_deflate_history(
@@ -526,11 +526,11 @@
   // 1st is the key in the first level table (9 bits).
   // 2nd is the key in the second level table (variable bits).
 
-  wuffs_deflate__decoder dec = ((wuffs_deflate__decoder){});
-  const char* status = wuffs_deflate__decoder__check_wuffs_version(
-      &dec, sizeof dec, WUFFS_VERSION);
+  wuffs_deflate__decoder dec;
+  const char* status =
+      wuffs_deflate__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
 
   int i;
diff --git a/test/c/std/gif.c b/test/c/std/gif.c
index 9c170c1..b9cf0f4 100644
--- a/test/c/std/gif.c
+++ b/test/c/std/gif.c
@@ -84,9 +84,9 @@
 
 const char* test_basic_bad_sizeof_receiver() {
   CHECK_FOCUS(__func__);
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
+  wuffs_gif__decoder dec;
   const char* status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, 0, WUFFS_VERSION);
+      wuffs_gif__decoder__initialize(&dec, 0, WUFFS_VERSION, 0);
   if (status != wuffs_base__error__bad_sizeof_receiver) {
     RETURN_FAIL("decode_image_config: got \"%s\", want \"%s\"", status,
                 wuffs_base__error__bad_sizeof_receiver);
@@ -96,9 +96,9 @@
 
 const char* test_basic_bad_wuffs_version() {
   CHECK_FOCUS(__func__);
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
-  const char* status = wuffs_gif__decoder__check_wuffs_version(
-      &dec, sizeof dec, WUFFS_VERSION ^ 0x123456789ABC);
+  wuffs_gif__decoder dec;
+  const char* status = wuffs_gif__decoder__initialize(
+      &dec, sizeof dec, WUFFS_VERSION ^ 0x123456789ABC, 0);
   if (status != wuffs_base__error__bad_wuffs_version) {
     RETURN_FAIL("decode_image_config: got \"%s\", want \"%s\"", status,
                 wuffs_base__error__bad_wuffs_version);
@@ -170,11 +170,11 @@
 
 const char* test_basic_sub_struct_initializer() {
   CHECK_FOCUS(__func__);
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
+  wuffs_gif__decoder dec;
   const char* status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+      wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
   if (dec.private_impl.magic != WUFFS_BASE__MAGIC) {
     RETURN_FAIL("outer magic: got %" PRIu32 ", want %" PRIu32 "",
@@ -192,9 +192,9 @@
 const char* wuffs_gif_decode(wuffs_base__io_buffer* dst,
                              wuffs_base__pixel_format pixfmt,
                              wuffs_base__io_buffer* src) {
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
+  wuffs_gif__decoder dec;
   const char* status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+      wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
     return status;
   }
@@ -259,11 +259,10 @@
     return status;
   }
 
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
-  status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+  wuffs_gif__decoder dec;
+  status = wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
 
   wuffs_base__frame_config fc = ((wuffs_base__frame_config){});
@@ -474,11 +473,10 @@
     return status;
   }
 
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
-  status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+  wuffs_gif__decoder dec;
+  status = wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
 
   {
@@ -521,11 +519,10 @@
     return status;
   }
 
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
-  status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+  wuffs_gif__decoder dec;
+  status = wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
 
   wuffs_base__io_reader src_reader = wuffs_base__io_buffer__reader(&src);
@@ -557,11 +554,10 @@
     return status;
   }
 
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
-  status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+  wuffs_gif__decoder dec;
+  status = wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
 
   wuffs_base__image_config ic = ((wuffs_base__image_config){});
@@ -681,11 +677,10 @@
     return status;
   }
 
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
-  status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+  wuffs_gif__decoder dec;
+  status = wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
   wuffs_base__image_config ic = ((wuffs_base__image_config){});
   wuffs_base__io_reader src_reader = wuffs_base__io_buffer__reader(&src);
@@ -861,11 +856,10 @@
     return status;
   }
 
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
-  status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+  wuffs_gif__decoder dec;
+  status = wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
   wuffs_base__image_config ic = ((wuffs_base__image_config){});
   wuffs_base__io_reader src_reader = wuffs_base__io_buffer__reader(&src);
@@ -896,11 +890,10 @@
   }
   src.meta.wi -= 2;
 
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
-  status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+  wuffs_gif__decoder dec;
+  status = wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
 
   wuffs_base__image_config ic = ((wuffs_base__image_config){});
@@ -944,11 +937,10 @@
     return status;
   }
 
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
-  status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+  wuffs_gif__decoder dec;
+  status = wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
   wuffs_base__image_config ic = ((wuffs_base__image_config){});
   wuffs_base__io_reader src_reader = wuffs_base__io_buffer__reader(&src);
@@ -1011,11 +1003,10 @@
     return status;
   }
 
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
-  status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+  wuffs_gif__decoder dec;
+  status = wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
 
   wuffs_base__image_config ic = ((wuffs_base__image_config){});
@@ -1075,11 +1066,10 @@
     return status;
   }
 
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
-  status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+  wuffs_gif__decoder dec;
+  status = wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
   wuffs_base__io_reader src_reader = wuffs_base__io_buffer__reader(&src);
 
@@ -1156,11 +1146,10 @@
     return status;
   }
 
-  wuffs_gif__decoder dec = ((wuffs_gif__decoder){});
-  status =
-      wuffs_gif__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+  wuffs_gif__decoder dec;
+  status = wuffs_gif__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
 
   wuffs_base__io_reader src_reader = wuffs_base__io_buffer__reader(&src);
diff --git a/test/c/std/gzip.c b/test/c/std/gzip.c
index 8094524..7d63039 100644
--- a/test/c/std/gzip.c
+++ b/test/c/std/gzip.c
@@ -87,9 +87,9 @@
                               wuffs_base__io_buffer* src,
                               uint64_t wlimit,
                               uint64_t rlimit) {
-  wuffs_gzip__decoder dec = ((wuffs_gzip__decoder){});
+  wuffs_gzip__decoder dec;
   const char* status =
-      wuffs_gzip__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+      wuffs_gzip__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
     return status;
   }
@@ -139,11 +139,11 @@
 
   int end_limit;
   for (end_limit = 0; end_limit < 10; end_limit++) {
-    wuffs_gzip__decoder dec = ((wuffs_gzip__decoder){});
-    status = wuffs_gzip__decoder__check_wuffs_version(&dec, sizeof dec,
-                                                      WUFFS_VERSION);
+    wuffs_gzip__decoder dec;
+    status =
+        wuffs_gzip__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
     if (status) {
-      RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+      RETURN_FAIL("initialize: \"%s\"", status);
     }
     wuffs_gzip__decoder__set_ignore_checksum(&dec, ignore_checksum);
     got.meta.wi = 0;
diff --git a/test/c/std/lzw.c b/test/c/std/lzw.c
index 67d726a..4ef4fc8 100644
--- a/test/c/std/lzw.c
+++ b/test/c/std/lzw.c
@@ -107,11 +107,10 @@
                 (int)(want_size));
   }
 
-  wuffs_lzw__decoder dec = ((wuffs_lzw__decoder){});
-  status =
-      wuffs_lzw__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+  wuffs_lzw__decoder dec;
+  status = wuffs_lzw__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
   wuffs_lzw__decoder__set_literal_width(&dec, literal_width);
   int num_iters = 0;
@@ -224,11 +223,11 @@
   src.data.ptr[2] = 0x43;
   src.data.ptr[3] = 0xFF;
 
-  wuffs_lzw__decoder dec = ((wuffs_lzw__decoder){});
+  wuffs_lzw__decoder dec;
   const char* status =
-      wuffs_lzw__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+      wuffs_lzw__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
   wuffs_lzw__decoder__set_literal_width(&dec, 7);
 
@@ -268,11 +267,11 @@
   src.data.ptr[0] = 0x01;
   src.data.ptr[1] = 0x01;
 
-  wuffs_lzw__decoder dec = ((wuffs_lzw__decoder){});
+  wuffs_lzw__decoder dec;
   const char* status =
-      wuffs_lzw__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+      wuffs_lzw__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
-    RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+    RETURN_FAIL("initialize: \"%s\"", status);
   }
   wuffs_lzw__decoder__set_literal_width(&dec, 8);
 
@@ -325,11 +324,10 @@
   for (i = 0; i < iters; i++) {
     got.meta.wi = 0;
     src.meta.ri = 1;  // Skip the literal width.
-    wuffs_lzw__decoder dec = ((wuffs_lzw__decoder){});
-    status = wuffs_lzw__decoder__check_wuffs_version(&dec, sizeof dec,
-                                                     WUFFS_VERSION);
+    wuffs_lzw__decoder dec;
+    status = wuffs_lzw__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
     if (status) {
-      RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+      RETURN_FAIL("initialize: \"%s\"", status);
     }
     status = wuffs_lzw__decoder__decode_io_writer(&dec, got_writer, src_reader,
                                                   global_work_slice);
diff --git a/test/c/std/zlib.c b/test/c/std/zlib.c
index 636b60e..0a4c517 100644
--- a/test/c/std/zlib.c
+++ b/test/c/std/zlib.c
@@ -87,9 +87,9 @@
                               wuffs_base__io_buffer* src,
                               uint64_t wlimit,
                               uint64_t rlimit) {
-  wuffs_zlib__decoder dec = ((wuffs_zlib__decoder){});
+  wuffs_zlib__decoder dec;
   const char* status =
-      wuffs_zlib__decoder__check_wuffs_version(&dec, sizeof dec, WUFFS_VERSION);
+      wuffs_zlib__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
   if (status) {
     return status;
   }
@@ -138,11 +138,11 @@
 
   int end_limit;
   for (end_limit = 0; end_limit < 10; end_limit++) {
-    wuffs_zlib__decoder dec = ((wuffs_zlib__decoder){});
-    status = wuffs_zlib__decoder__check_wuffs_version(&dec, sizeof dec,
-                                                      WUFFS_VERSION);
+    wuffs_zlib__decoder dec;
+    status =
+        wuffs_zlib__decoder__initialize(&dec, sizeof dec, WUFFS_VERSION, 0);
     if (status) {
-      RETURN_FAIL("check_wuffs_version: \"%s\"", status);
+      RETURN_FAIL("initialize: \"%s\"", status);
     }
     wuffs_zlib__decoder__set_ignore_checksum(&dec, ignore_checksum);
     got.meta.wi = 0;