Ported upb to C89, for greater portability.

A large part of this change contains surface-level
porting, like moving variable declarations to the
top of the block.

However there are a few more substantial things too:

- moved internal-only struct definitions to a separate
  file (structdefs.int.h), for greater encapsulation
  and ABI compatibility.

- removed the UPB_UPCAST macro, since it requires access
  to the internal-only struct definitions.  Replaced uses
  with calls to inline, type-safe casting functions.

- removed the UPB_DEFINE_CLASS/UPB_DEFINE_STRUCT macros.
  Class and struct definitions are now more explicit -- you
  get to see the actual class/struct keywords in the source.
  The casting convenience functions have been moved into
  UPB_DECLARE_DERIVED_TYPE() and UPB_DECLARE_DERIVED_TYPE2().

- the new way that we duplicate base methods in derived types
  is also more convenient and requires less duplication.
  It is also less greppable, but hopefully that is not
  too big a problem.

Compiler flags (-std=c89 -pedantic) should help to rigorously
enforce that the code is free of C99-isms.

A few functions are not available in C89 (strtoll).  There
are temporary, hacky solutions in place.

5 files changed, 164 insertions, 123 deletions

diff --git a/tests/pb/test_decoder.cc b/tests/pb/test_decoder.cc
index 98926a6..c615a3c 100644
--- a/tests/pb/test_decoder.cc
+++ b/tests/pb/test_decoder.cc
@@ -111,7 +111,7 @@ using std::string;
 
 void vappendf(string* str, const char *format, va_list args) {
   va_list copy;
-  va_copy(copy, args);
+  __va_copy(copy, args);
 
   int count = vsnprintf(NULL, 0, format, args);
   if (count >= 0)
@@ -577,7 +577,7 @@ void run_decoder(const string& proto, const string* expected_output) {
           fprintf(stderr, "RUNNING TEST CASE, hash=%x\n", testhash);
           fprintf(stderr, "JIT on: %s\n",
                   global_method->is_native() ? "true" : "false");
-          fprintf(stderr, "Input (len=%zu): ", proto.size());
+          fprintf(stderr, "Input (len=%u): ", (unsigned)proto.size());
           PrintBinary(proto);
           fprintf(stderr, "\n");
           if (expected_output) {
diff --git a/tests/pb/test_varint.c b/tests/pb/test_varint.c
index 84ff831..c80f127 100644
--- a/tests/pb/test_varint.c
+++ b/tests/pb/test_varint.c
@@ -8,25 +8,30 @@
 #include "upb/pb/varint.int.h"
 #include "tests/upb_test.h"
 
-// Test that we can round-trip from int->varint->int.
+/* Test that we can round-trip from int->varint->int. */
 static void test_varint_for_num(upb_decoderet (*decoder)(const char*),
                                 uint64_t num) {
   char buf[16];
+  size_t bytes;
+  upb_decoderet r;
+
   memset(buf, 0xff, sizeof(buf));
-  size_t bytes = upb_vencode64(num, buf);
+  bytes = upb_vencode64(num, buf);
 
   if (num <= UINT32_MAX) {
+    uint64_t encoded = upb_vencode32(num);
     char buf2[16];
+    upb_decoderet r;
+
     memset(buf2, 0, sizeof(buf2));
-    uint64_t encoded = upb_vencode32(num);
     memcpy(&buf2, &encoded, 8);
-    upb_decoderet r = decoder(buf2);
+    r = decoder(buf2);
     ASSERT(r.val == num);
     ASSERT(r.p == buf2 + upb_value_size(encoded));
     ASSERT(upb_zzenc_32(upb_zzdec_32(num)) == num);
   }
 
-  upb_decoderet r = decoder(buf);
+  r = decoder(buf);
   ASSERT(r.val == num);
   ASSERT(r.p == buf + bytes);
   ASSERT(upb_zzenc_64(upb_zzdec_64(num)) == num);
@@ -36,13 +41,23 @@ static void test_varint_decoder(upb_decoderet (*decoder)(const char*)) {
 #define TEST(bytes, expected_val) {\
     size_t n = sizeof(bytes) - 1;  /* for NULL */ \
     char buf[UPB_PB_VARINT_MAX_LEN]; \
+    upb_decoderet r; \
     memset(buf, 0xff, sizeof(buf)); \
     memcpy(buf, bytes, n); \
-    upb_decoderet r = decoder(buf); \
+    r = decoder(buf); \
     ASSERT(r.val == expected_val); \
     ASSERT(r.p == buf + n); \
   }
 
+  uint64_t num;
+
+  char twelvebyte[16] = {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 1, 1};
+  const char *twelvebyte_buf = twelvebyte;
+  /* A varint that terminates before hitting the end of the provided buffer,
+   * but in too many bytes (11 instead of 10). */
+  upb_decoderet r = decoder(twelvebyte_buf);
+  ASSERT(r.p == NULL);
+
   TEST("\x00",                                                      0ULL);
   TEST("\x01",                                                      1ULL);
   TEST("\x81\x14",                                              0xa01ULL);
@@ -57,16 +72,7 @@ static void test_varint_decoder(upb_decoderet (*decoder)(const char*)) {
   TEST("\x81\x83\x87\x8f\x9f\xbf\xff\x81\x83\x07", 0x8303fdf9f1e1c181ULL);
 #undef TEST
 
-  char twelvebyte[16] = {0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
-                         0x80, 0x01, 0x01};
-  const char *twelvebyte_buf = twelvebyte;
-  // A varint that terminates before hitting the end of the provided buffer,
-  // but in too many bytes (11 instead of 10).
-  upb_decoderet r = decoder(twelvebyte_buf);
-  ASSERT(r.p == NULL);
-
-
-  for (uint64_t num = 5; num * 1.5 < UINT64_MAX; num *= 1.5) {
+  for (num = 5; num * 1.5 < UINT64_MAX; num *= 1.5) {
     test_varint_for_num(decoder, num);
   }
   test_varint_for_num(decoder, 0);
@@ -80,16 +86,13 @@ static void test_varint_decoder(upb_decoderet (*decoder)(const char*)) {
     return upb_vdecode_ ## decoder(p); \
   } \
   void test_ ## decoder() { \
-    printf("Testing varint decoder: " #decoder "..."); \
-    fflush(stdout); \
     test_varint_decoder(&_upb_vdecode_ ## decoder); \
-    printf("ok.\n"); \
   } \
 
-TEST_VARINT_DECODER(check2_branch32);
-TEST_VARINT_DECODER(check2_branch64);
-TEST_VARINT_DECODER(check2_wright);
-TEST_VARINT_DECODER(check2_massimino);
+TEST_VARINT_DECODER(check2_branch32)
+TEST_VARINT_DECODER(check2_branch64)
+TEST_VARINT_DECODER(check2_wright)
+TEST_VARINT_DECODER(check2_massimino)
 
 int run_tests(int argc, char *argv[]) {
   UPB_UNUSED(argc);
diff --git a/tests/test_def.c b/tests/test_def.c
index fed2b74..4f9fcff 100644
--- a/tests/test_def.c
+++ b/tests/test_def.c
@@ -20,23 +20,23 @@ static void test_empty_symtab() {
   upb_symtab_iter i;
   for (upb_symtab_begin(&i, s, UPB_DEF_ANY); !upb_symtab_done(&i);
        upb_symtab_next(&i)) {
-    ASSERT(false);  // Should not get here.
+    ASSERT(false);  /* Should not get here. */
   }
   upb_symtab_unref(s, &s);
 }
 
 static void test_noreftracking() {
-  // Reftracking is not required; clients can pass UPB_UNTRACKED_REF for owner.
+  /* Reftracking is not required; clients can pass UPB_UNTRACKED_REF for owner. */
   upb_msgdef *md = upb_msgdef_new(UPB_UNTRACKED_REF);
   upb_msgdef_ref(md, UPB_UNTRACKED_REF);
 
-  // Clients can mix tracked and untracked refs.
+  /* Clients can mix tracked and untracked refs. */
   upb_msgdef_ref(md, &md);
 
   upb_msgdef_unref(md, UPB_UNTRACKED_REF);
   upb_msgdef_unref(md, UPB_UNTRACKED_REF);
 
-  // Call some random function on the messagedef to test that it is alive.
+  /* Call some random function on the messagedef to test that it is alive. */
   ASSERT(!upb_msgdef_isfrozen(md));
 
   upb_msgdef_unref(md, &md);
@@ -44,8 +44,8 @@ static void test_noreftracking() {
 
 static upb_symtab *load_test_proto(void *owner) {
   upb_symtab *s = upb_symtab_new(owner);
-  ASSERT(s);
   upb_status status = UPB_STATUS_INIT;
+  ASSERT(s);
   if (!upb_load_descriptor_file_into_symtab(s, descriptor_file, &status)) {
     fprintf(stderr, "Error loading descriptor file: %s\n",
             upb_status_errmsg(&status));
@@ -58,60 +58,73 @@ static upb_symtab *load_test_proto(void *owner) {
 }
 
 static void test_cycles() {
+  bool ok;
   upb_symtab *s = load_test_proto(&s);
-
-  // Test cycle detection by making a cyclic def's main refcount go to zero
-  // and then be incremented to one again.
-  const upb_def *def = upb_symtab_lookup(s, "A");
+  const upb_msgdef *m;
+  const upb_fielddef *f;
+  const upb_def *def;
+  const upb_def *def2;
+
+  /* Test cycle detection by making a cyclic def's main refcount go to zero
+   * and then be incremented to one again. */
+  def = upb_symtab_lookup(s, "A");
   upb_def_ref(def, &def);
   ASSERT(def);
   ASSERT(upb_def_isfrozen(def));
   upb_symtab_unref(s, &s);
 
-  // Message A has only one subfield: "optional B b = 1".
-  const upb_msgdef *m = upb_downcast_msgdef(def);
-  const upb_fielddef *f = upb_msgdef_itof(m, 1);
+  /* Message A has only one subfield: "optional B b = 1". */
+  m = upb_downcast_msgdef(def);
+  f = upb_msgdef_itof(m, 1);
   ASSERT(f);
   ASSERT(upb_fielddef_hassubdef(f));
   ASSERT(upb_msgdef_ntofz(m, "b") == f);
   ASSERT(upb_msgdef_ntof(m, "b", 1) == f);
-  const upb_def *def2 = upb_fielddef_subdef(f);
+  def2 = upb_fielddef_subdef(f);
   ASSERT(upb_downcast_msgdef(def2));
-  ASSERT(strcmp(upb_def_fullname(def2), "B") == 0);
+  ok = strcmp(upb_def_fullname(def2), "B") == 0;
+  ASSERT(ok);
 
   upb_def_ref(def2, &def2);
   upb_def_unref(def, &def);
 
-  // We know "def" is still alive because it's reachable from def2.
-  ASSERT(strcmp(upb_def_fullname(def), "A") == 0);
+  /* We know "def" is still alive because it's reachable from def2. */
+  ok = strcmp(upb_def_fullname(def), "A") == 0;
+  ASSERT(ok);
   upb_def_unref(def2, &def2);
 }
 
 static void test_symbol_resolution() {
   upb_status s = UPB_STATUS_INIT;
+  upb_def *defs[2];
+  upb_msgdef *m1;
+  upb_msgdef *m2;
+  upb_msgdef *m3;
+  upb_fielddef *m3_field1;
+  upb_fielddef *m3_field2;
 
   upb_symtab *symtab = upb_symtab_new(&symtab);
   ASSERT(symtab);
 
-  // m1 has name "A.B.C" and no fields. We'll add it to the symtab now.
-  upb_msgdef *m1 = upb_msgdef_new(&m1);
+  /* m1 has name "A.B.C" and no fields. We'll add it to the symtab now. */
+  m1 = upb_msgdef_new(&m1);
   ASSERT(m1);
   ASSERT_STATUS(upb_msgdef_setfullname(m1, "A.B.C", &s), &s);
   ASSERT_STATUS(upb_symtab_add(symtab, (upb_def**)&m1, 1,
                                NULL, &s), &s);
 
-  // m2 has name "D.E" and no fields. We'll add it in the same batch as m3
-  // below.
-  upb_msgdef *m2 = upb_msgdef_new(&m2);
+  /* m2 has name "D.E" and no fields. We'll add it in the same batch as m3
+   * below. */
+  m2 = upb_msgdef_new(&m2);
   ASSERT(m2);
   ASSERT_STATUS(upb_msgdef_setfullname(m2, "D.E", &s), &s);
 
-  // m3 has name "F.G" and two fields, of type A.B.C and D.E respectively. We'll
-  // add it in the same batch as m2 above.
-  upb_msgdef *m3 = upb_msgdef_new(&m3);
+  /* m3 has name "F.G" and two fields, of type A.B.C and D.E respectively. We'll
+   * add it in the same batch as m2 above. */
+  m3 = upb_msgdef_new(&m3);
   ASSERT(m3);
   ASSERT_STATUS(upb_msgdef_setfullname(m3, "F.G", &s), &s);
-  upb_fielddef *m3_field1 = upb_fielddef_new(&m3_field1);
+  m3_field1 = upb_fielddef_new(&m3_field1);
   ASSERT_STATUS(upb_fielddef_setname(m3_field1, "field1", &s), &s);
   ASSERT_STATUS(upb_fielddef_setnumber(m3_field1, 1, &s), &s);
   upb_fielddef_setlabel(m3_field1, UPB_LABEL_OPTIONAL);
@@ -119,7 +132,7 @@ static void test_symbol_resolution() {
   ASSERT_STATUS(upb_fielddef_setsubdefname(m3_field1, ".A.B.C", &s), &s);
   ASSERT_STATUS(upb_msgdef_addfield(m3, m3_field1, NULL, &s), &s);
 
-  upb_fielddef *m3_field2 = upb_fielddef_new(&m3_field2);
+  m3_field2 = upb_fielddef_new(&m3_field2);
   ASSERT_STATUS(upb_fielddef_setname(m3_field2, "field2", &s), &s);
   ASSERT_STATUS(upb_fielddef_setnumber(m3_field2, 2, &s), &s);
   upb_fielddef_setlabel(m3_field2, UPB_LABEL_OPTIONAL);
@@ -127,7 +140,8 @@ static void test_symbol_resolution() {
   ASSERT_STATUS(upb_fielddef_setsubdefname(m3_field2, ".D.E", &s), &s);
   ASSERT_STATUS(upb_msgdef_addfield(m3, m3_field2, NULL, &s), &s);
 
-  upb_def *defs[2] = { (upb_def*)m2, (upb_def*)m3 };
+  defs[0] = upb_msgdef_upcast_mutable(m2);
+  defs[1] = upb_msgdef_upcast_mutable(m3);
   ASSERT_STATUS(upb_symtab_add(symtab, defs, 2, NULL, &s), &s);
 
   upb_fielddef_unref(m3_field2, &m3_field2);
@@ -139,22 +153,24 @@ static void test_symbol_resolution() {
 }
 
 static void test_fielddef_unref() {
+  bool ok;
   upb_symtab *s = load_test_proto(&s);
   const upb_msgdef *md = upb_symtab_lookupmsg(s, "A");
   const upb_fielddef *f = upb_msgdef_itof(md, 1);
   upb_fielddef_ref(f, &f);
 
-  // Unref symtab; now fielddef is the only thing keeping the msgdef alive.
+  /* Unref symtab; now fielddef is the only thing keeping the msgdef alive. */
   upb_symtab_unref(s, &s);
-  // Check that md is still alive.
-  ASSERT(strcmp(upb_msgdef_fullname(md), "A") == 0);
+  /* Check that md is still alive. */
+  ok = strcmp(upb_msgdef_fullname(md), "A") == 0;
+  ASSERT(ok);
 
-  // Check that unref of fielddef frees the whole remaining graph.
+  /* Check that unref of fielddef frees the whole remaining graph. */
   upb_fielddef_unref(f, &f);
 }
 
 static void test_fielddef() {
-  // Test that we don't leak an unresolved subdef name.
+  /* Test that we don't leak an unresolved subdef name. */
   upb_fielddef *f1 = upb_fielddef_new(&f1);
   upb_fielddef_settype(f1, UPB_TYPE_MESSAGE);
   ASSERT(upb_fielddef_setsubdefname(f1, "YO", NULL));
@@ -189,51 +205,61 @@ static upb_enumdef *upb_enumdef_newnamed(const char *name, void *owner) {
 
 static void test_replacement() {
   upb_symtab *s = upb_symtab_new(&s);
+  upb_enumdef *e2;
+  upb_msgdef *m2;
+  upb_enumdef *e;
+  upb_status status = UPB_STATUS_INIT;
+  upb_def *newdefs[3];
+  upb_def *newdefs2[1];
+  const upb_msgdef *m3;
 
   upb_msgdef *m = upb_msgdef_newnamed("MyMessage", &s);
   upb_msgdef_addfield(m, newfield("field1", 1, UPB_TYPE_ENUM,
                                   UPB_LABEL_OPTIONAL, ".MyEnum", &s),
                       &s, NULL);
-  upb_msgdef *m2 = upb_msgdef_newnamed("MyMessage2", &s);
-  upb_enumdef *e = upb_enumdef_newnamed("MyEnum", &s);
-  upb_status status = UPB_STATUS_INIT;
+  m2 = upb_msgdef_newnamed("MyMessage2", &s);
+  e = upb_enumdef_newnamed("MyEnum", &s);
   ASSERT_STATUS(upb_enumdef_addval(e, "VAL1", 1, &status), &status);
 
-  upb_def *newdefs[] = {UPB_UPCAST(m), UPB_UPCAST(m2), UPB_UPCAST(e)};
+  newdefs[0] = upb_msgdef_upcast_mutable(m);
+  newdefs[1] = upb_msgdef_upcast_mutable(m2);
+  newdefs[2] = upb_enumdef_upcast_mutable(e);
   ASSERT_STATUS(upb_symtab_add(s, newdefs, 3, &s, &status), &status);
 
-  // Try adding a new definition of MyEnum, MyMessage should get replaced with
-  // a new version.
-  upb_enumdef *e2 = upb_enumdef_newnamed("MyEnum", &s);
+  /* Try adding a new definition of MyEnum, MyMessage should get replaced with
+   * a new version. */
+  e2 = upb_enumdef_newnamed("MyEnum", &s);
   ASSERT_STATUS(upb_enumdef_addval(e2, "VAL1", 1, &status), &status);
-  upb_def *newdefs2[] = {UPB_UPCAST(e2)};
+  newdefs2[0] = upb_enumdef_upcast_mutable(e2);
   ASSERT_STATUS(upb_symtab_add(s, newdefs2, 1, &s, &status), &status);
 
-  const upb_msgdef *m3 = upb_symtab_lookupmsg(s, "MyMessage");
+  m3 = upb_symtab_lookupmsg(s, "MyMessage");
   ASSERT(m3);
-  // Must be different because it points to MyEnum which was replaced.
+  /* Must be different because it points to MyEnum which was replaced. */
   ASSERT(m3 != m);
 
   m3 = upb_symtab_lookupmsg(s, "MyMessage2");
-  // Should be the same because it was not replaced, nor were any defs that
-  // are reachable from it.
+  /* Should be the same because it was not replaced, nor were any defs that
+   * are reachable from it. */
   ASSERT(m3 == m2);
 
   upb_symtab_unref(s, &s);
 }
 
 static void test_freeze_free() {
-  // Test that freeze frees defs that were only being kept alive by virtue of
-  // sharing a group with other defs that are being frozen.
+  bool ok;
+
+  /* Test that freeze frees defs that were only being kept alive by virtue of
+   * sharing a group with other defs that are being frozen. */
   upb_msgdef *m1 = upb_msgdef_newnamed("M1", &m1);
   upb_msgdef *m2 = upb_msgdef_newnamed("M2", &m2);
   upb_msgdef *m3 = upb_msgdef_newnamed("M3", &m3);
   upb_msgdef *m4 = upb_msgdef_newnamed("M4", &m4);
+  upb_fielddef *f = upb_fielddef_new(&f);
 
-  // Freeze M4 and make M1 point to it.
+  /* Freeze M4 and make M1 point to it. */
   upb_def_freeze((upb_def*const*)&m4, 1, NULL);
 
-  upb_fielddef *f = upb_fielddef_new(&f);
   upb_fielddef_settype(f, UPB_TYPE_MESSAGE);
   ASSERT(upb_fielddef_setnumber(f, 1, NULL));
   ASSERT(upb_fielddef_setname(f, "foo", NULL));
@@ -241,10 +267,10 @@ static void test_freeze_free() {
 
   ASSERT(upb_msgdef_addfield(m1, f, &f, NULL));
 
-  // After this unref, M1 is the only thing keeping M4 alive.
+  /* After this unref, M1 is the only thing keeping M4 alive. */
   upb_msgdef_unref(m4, &m4);
 
-  // Force M1/M2/M3 into a single mutable refcounting group.
+  /* Force M1/M2/M3 into a single mutable refcounting group. */
   f = upb_fielddef_new(&f);
   upb_fielddef_settype(f, UPB_TYPE_MESSAGE);
   ASSERT(upb_fielddef_setnumber(f, 1, NULL));
@@ -254,40 +280,45 @@ static void test_freeze_free() {
   ASSERT(upb_fielddef_setmsgsubdef(f, m2, NULL));
   ASSERT(upb_fielddef_setmsgsubdef(f, m3, NULL));
 
-  // Make M3 cyclic with itself.
+  /* Make M3 cyclic with itself. */
   ASSERT(upb_msgdef_addfield(m3, f, &f, NULL));
 
-  // These will be kept alive since they are in the same refcounting group as
-  // M3, which still has a ref.  Note: this behavior is not guaranteed by the
-  // API, but true in practice with its current implementation.
+  /* These will be kept alive since they are in the same refcounting group as
+   * M3, which still has a ref.  Note: this behavior is not guaranteed by the
+   * API, but true in practice with its current implementation. */
   upb_msgdef_unref(m1, &m1);
   upb_msgdef_unref(m2, &m2);
 
-  // Test that they are still alive (NOT allowed by the API).
-  ASSERT(strcmp("M1", upb_msgdef_fullname(m1)) == 0);
-  ASSERT(strcmp("M2", upb_msgdef_fullname(m2)) == 0);
+  /* Test that they are still alive (NOT allowed by the API). */
+  ok = strcmp("M1", upb_msgdef_fullname(m1)) == 0;
+  ASSERT(ok);
+  ok = strcmp("M2", upb_msgdef_fullname(m2)) == 0;
+  ASSERT(ok);
 
-  // Freeze M3.  If the test leaked no memory, then freeing m1 and m2 was
-  // successful.
+  /* Freeze M3.  If the test leaked no memory, then freeing m1 and m2 was
+   * successful. */
   ASSERT(upb_def_freeze((upb_def*const*)&m3, 1, NULL));
 
   upb_msgdef_unref(m3, &m3);
 }
 
 static void test_partial_freeze() {
-  // Test that freeze of only part of the graph correctly adjusts objects that
-  // point to the newly-frozen objects.
+  /* Test that freeze of only part of the graph correctly adjusts objects that
+   * point to the newly-frozen objects. */
   upb_msgdef *m1 = upb_msgdef_newnamed("M1", &m1);
   upb_msgdef *m2 = upb_msgdef_newnamed("M2", &m2);
   upb_msgdef *m3 = upb_msgdef_newnamed("M3", &m3);
-
   upb_fielddef *f1 = upb_fielddef_new(&f1);
+  upb_fielddef *f2 = upb_fielddef_new(&f2);
+  upb_def *defs[2];
+  defs[0] = upb_msgdef_upcast_mutable(m1);
+  defs[1] = upb_msgdef_upcast_mutable(m2);
+
   upb_fielddef_settype(f1, UPB_TYPE_MESSAGE);
   ASSERT(upb_fielddef_setnumber(f1, 1, NULL));
   ASSERT(upb_fielddef_setname(f1, "f1", NULL));
   ASSERT(upb_fielddef_setmsgsubdef(f1, m1, NULL));
 
-  upb_fielddef *f2 = upb_fielddef_new(&f2);
   upb_fielddef_settype(f2, UPB_TYPE_MESSAGE);
   ASSERT(upb_fielddef_setnumber(f2, 2, NULL));
   ASSERT(upb_fielddef_setname(f2, "f2", NULL));
@@ -296,9 +327,8 @@ static void test_partial_freeze() {
   ASSERT(upb_msgdef_addfield(m3, f1, &f1, NULL));
   ASSERT(upb_msgdef_addfield(m3, f2, &f2, NULL));
 
-  // Freeze M1 and M2, which should cause the group to be split
-  // and m3 (left mutable) to take references on m1 and m2.
-  upb_def *defs[] = {UPB_UPCAST(m1), UPB_UPCAST(m2)};
+  /* Freeze M1 and M2, which should cause the group to be split
+   * and m3 (left mutable) to take references on m1 and m2. */
   ASSERT(upb_def_freeze(defs, 2, NULL));
 
   ASSERT(upb_msgdef_isfrozen(m1));
@@ -312,13 +342,15 @@ static void test_partial_freeze() {
 
 static void test_descriptor_flags() {
   upb_msgdef *m = upb_msgdef_new(&m);
-  ASSERT(upb_msgdef_mapentry(m) == false);
+  upb_msgdef *m2;
   upb_status s = UPB_STATUS_INIT;
+
+  ASSERT(upb_msgdef_mapentry(m) == false);
   upb_msgdef_setfullname(m, "TestMessage", &s);
   ASSERT(upb_ok(&s));
   upb_msgdef_setmapentry(m, true);
   ASSERT(upb_msgdef_mapentry(m) == true);
-  upb_msgdef *m2 = upb_msgdef_dup(m, &m2);
+  m2 = upb_msgdef_dup(m, &m2);
   ASSERT(upb_msgdef_mapentry(m2) == true);
   upb_msgdef_unref(m, &m);
   upb_msgdef_unref(m2, &m2);
@@ -326,10 +358,13 @@ static void test_descriptor_flags() {
 
 static void test_mapentry_check() {
   upb_status s = UPB_STATUS_INIT;
-
   upb_msgdef *m = upb_msgdef_new(&m);
-  upb_msgdef_setfullname(m, "TestMessage", &s);
   upb_fielddef *f = upb_fielddef_new(&f);
+  upb_symtab *symtab = upb_symtab_new(&symtab);
+  upb_msgdef *subm = upb_msgdef_new(&subm);
+  upb_def *defs[2];
+
+  upb_msgdef_setfullname(m, "TestMessage", &s);
   upb_fielddef_setname(f, "field1", &s);
   upb_fielddef_setnumber(f, 1, &s);
   upb_fielddef_setlabel(f, UPB_LABEL_OPTIONAL);
@@ -338,14 +373,13 @@ static void test_mapentry_check() {
   upb_msgdef_addfield(m, f, &f, &s);
   ASSERT(upb_ok(&s));
 
-  upb_msgdef *subm = upb_msgdef_new(&subm);
   upb_msgdef_setfullname(subm, "MapEntry", &s);
   upb_msgdef_setmapentry(subm, true);
 
-  upb_symtab *symtab = upb_symtab_new(&symtab);
-  upb_def *defs[] = {UPB_UPCAST(m), UPB_UPCAST(subm)};
+  defs[0] = upb_msgdef_upcast_mutable(m);
+  defs[1] = upb_msgdef_upcast_mutable(subm);
   upb_symtab_add(symtab, defs, 2, NULL, &s);
-  // Should not have succeeded: non-repeated field pointing to a MapEntry.
+  /* Should not have succeeded: non-repeated field pointing to a MapEntry. */
   ASSERT(!upb_ok(&s));
 
   upb_fielddef_setlabel(f, UPB_LABEL_REPEATED);
@@ -360,22 +394,26 @@ static void test_mapentry_check() {
 static void test_oneofs() {
   upb_status s = UPB_STATUS_INIT;
   bool ok = true;
-
+  upb_def *subm_defs[1];
   upb_symtab *symtab = upb_symtab_new(&symtab);
+  upb_msgdef *subm = upb_msgdef_newnamed("SubMessage", &symtab);
+  upb_msgdef *m = upb_msgdef_newnamed("TestMessage", &symtab);
+  upb_oneofdef *o = upb_oneofdef_new(&o);
+  const upb_oneofdef *lookup_o;
+  const upb_fielddef *lookup_field;
+  upb_def *defs[1];
+
   ASSERT(symtab != NULL);
 
-  // Create a test message for fields to refer to.
-  upb_msgdef *subm = upb_msgdef_newnamed("SubMessage", &symtab);
+  /* Create a test message for fields to refer to. */
   upb_msgdef_addfield(subm, newfield("field1", 1, UPB_TYPE_INT32,
                                      UPB_LABEL_OPTIONAL, NULL, &symtab),
                       &symtab, NULL);
-  upb_def *subm_defs[] = {UPB_UPCAST(subm)};
+  subm_defs[0] = upb_msgdef_upcast_mutable(subm);
   ASSERT_STATUS(upb_symtab_add(symtab, subm_defs, 1, &symtab, &s), &s);
 
-  upb_msgdef *m = upb_msgdef_newnamed("TestMessage", &symtab);
   ASSERT(upb_msgdef_numoneofs(m) == 0);
 
-  upb_oneofdef *o = upb_oneofdef_new(&o);
   ASSERT(upb_oneofdef_numfields(o) == 0);
   ASSERT(upb_oneofdef_name(o) == NULL);
 
@@ -395,14 +433,14 @@ static void test_oneofs() {
   ok = upb_msgdef_addoneof(m, o, NULL, &s);
   ASSERT_STATUS(ok, &s);
 
-  upb_def *defs[] = {UPB_UPCAST(m)};
+  defs[0] = upb_msgdef_upcast_mutable(m);
   ASSERT_STATUS(upb_symtab_add(symtab, defs, 1, &symtab, &s), &s);
 
   ASSERT(upb_msgdef_numoneofs(m) == 1);
-  const upb_oneofdef *lookup_o = upb_msgdef_ntooz(m, "test_oneof");
+  lookup_o = upb_msgdef_ntooz(m, "test_oneof");
   ASSERT(lookup_o == o);
 
-  const upb_fielddef *lookup_field = upb_oneofdef_ntofz(o, "field1");
+  lookup_field = upb_oneofdef_ntofz(o, "field1");
   ASSERT(lookup_field != NULL && upb_fielddef_number(lookup_field) == 1);
 
   upb_symtab_unref(symtab, &symtab);
diff --git a/tests/test_handlers.c b/tests/test_handlers.c
index 951f2c5..be95c0a 100644
--- a/tests/test_handlers.c
+++ b/tests/test_handlers.c
@@ -18,13 +18,13 @@ static bool startmsg(void *c, const void *hd) {
 }
 
 static void test_error() {
-  // Test creating handlers of a static msgdef.
+  /* Test creating handlers of a static msgdef. */
   const upb_symtab *s = upbdefs_google_protobuf_descriptor(&s);
   upb_handlers *h =
       upb_handlers_new(upbdefs_google_protobuf_DescriptorProto(s), &h);
   upb_symtab_unref(s, &s);
 
-  // Attempt to set the same handler twice causes error.
+  /* Attempt to set the same handler twice causes error. */
   ASSERT(upb_ok(upb_handlers_status(h)));
   upb_handlers_setstartmsg(h, &startmsg, NULL);
   ASSERT(upb_ok(upb_handlers_status(h)));
@@ -32,7 +32,7 @@ static void test_error() {
   ASSERT(!upb_ok(upb_handlers_status(h)));
   ASSERT(!upb_handlers_freeze(&h, 1, NULL));
 
-  // Clearing the error will let us proceed.
+  /* Clearing the error will let us proceed. */
   upb_handlers_clearerr(h);
   ASSERT(upb_handlers_freeze(&h, 1, NULL));
   ASSERT(upb_handlers_isfrozen(h));
diff --git a/tests/test_util.h b/tests/test_util.h
index 27c2bb3..73a5c19 100644
--- a/tests/test_util.h
+++ b/tests/test_util.h
@@ -38,8 +38,8 @@ bool parse_buffer(upb::BytesSink* sink, void* subc, const char* buf,
     memcpy(buf2, buf + start, len);
 
     if (verbose) {
-      fprintf(stderr, "Calling parse(%zu) for bytes %zu-%zu of the input\n",
-              len, start, end);
+      fprintf(stderr, "Calling parse(%u) for bytes %u-%u of the input\n",
+              (unsigned)len, (unsigned)start, (unsigned)end);
     }
 
     size_t parsed = sink->PutBuffer(subc, buf2, len, &global_handle);
@@ -48,18 +48,18 @@ bool parse_buffer(upb::BytesSink* sink, void* subc, const char* buf,
     if (verbose) {
       if (parsed == len) {
         fprintf(stderr,
-                "parse(%zu) = %zu, complete byte count indicates success\n",
-                len, len);
+                "parse(%u) = %u, complete byte count indicates success\n",
+                (unsigned)len, (unsigned)len);
       } else if (parsed > len) {
         fprintf(stderr,
-                "parse(%zu) = %zu, long byte count indicates success and skip"
-                "of the next %zu bytes\n",
-                len, parsed, parsed - len);
+                "parse(%u) = %u, long byte count indicates success and skip"
+                "of the next %u bytes\n",
+                (unsigned)len, (unsigned)parsed, (unsigned)(parsed - len));
       } else {
         fprintf(stderr,
-                "parse(%zu) = %zu, short byte count indicates failure; "
-                "last %zu bytes were not consumed\n",
-                len, parsed, len - parsed);
+                "parse(%u) = %u, short byte count indicates failure; "
+                "last %u bytes were not consumed\n",
+                (unsigned)len, (unsigned)parsed, (unsigned)(len - parsed));
       }
     }
 
@@ -73,8 +73,8 @@ bool parse_buffer(upb::BytesSink* sink, void* subc, const char* buf,
                 "Error: decode function returned complete byte count but set "
                 "error status\n");
       }
-      fprintf(stderr, "Status: %s, parsed=%zu, len=%zu\n",
-              status->error_message(), parsed, len);
+      fprintf(stderr, "Status: %s, parsed=%u, len=%u\n",
+              status->error_message(), (unsigned)parsed, (unsigned)len);
       ASSERT(false);
     }