Update spec test suite (#2484)

This updates spec test suite to that of the current up-to-date version
of https://github.com/WebAssembly/spec repo.

- All failing tests are added in `BLACKLIST` in shared.py with reasons.
 - For tests that already existed and was passing and started failing
   after the update, we add the new test to the blacklist and preserve
   the old file by renaming it to 'old_[FILENAME].wast' not to lose test
   coverage. When the cause of the error is fixed or the unsupported
   construct gets support so the new test passes, we can delete the
   corresponding 'old_[FILENAME].wast' file.
- Adds support for `spectest.print_[type] style imports.

1 files changed, 1792 insertions, 0 deletions

diff --git a/test/spec/utf8-custom-section-id.wast b/test/spec/utf8-custom-section-id.wast
new file mode 100644
index 000000000..129d2b913
--- /dev/null
+++ b/test/spec/utf8-custom-section-id.wast
@@ -0,0 +1,1792 @@
+;;;;;; Invalid UTF-8 custom section names
+
+;;;; Continuation bytes not preceded by prefixes
+
+;; encoding starts with (first) continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\80"                       ;; "\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; encoding starts with (0x8f) continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\8f"                       ;; "\8f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; encoding starts with (0x90) continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\90"                       ;; "\90"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; encoding starts with (0x9f) continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\9f"                       ;; "\9f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; encoding starts with (0xa0) continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\a0"                       ;; "\a0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; encoding starts with (last) continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\bf"                       ;; "\bf"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 2-byte sequences
+
+;; 2-byte sequence contains 3 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\c2\80\80"                 ;; "\c2\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 2-byte sequence contains 1 byte at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\c2"                       ;; "\c2"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 2-byte sequence contains 1 byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\c2\2e"                    ;; "\c2."
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 2-byte sequence contents
+
+;; overlong encoding after 0xc0 prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\c0\80"                    ;; "\c0\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; overlong encoding after 0xc0 prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\c0\bf"                    ;; "\c0\bf"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; overlong encoding after 0xc1 prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\c1\80"                    ;; "\c1\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; overlong encoding after 0xc1 prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\c1\bf"                    ;; "\c1\bf"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; byte after (first) 2-byte prefix not a contination byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\c2\00"                    ;; "\c2\00"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; byte after (first) 2-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\c2\7f"                    ;; "\c2\7f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; byte after (first) 2-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\c2\c0"                    ;; "\c2\c0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; byte after (first) 2-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\c2\fd"                    ;; "\c2\fd"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; byte after (last) 2-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\df\00"                    ;; "\df\00"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; byte after (last) 2-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\df\7f"                    ;; "\df\7f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; byte after (last) 2-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\df\c0"                    ;; "\df\c0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; byte after (last) 2-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\df\fd"                    ;; "\df\fd"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 3-byte sequences
+
+;; 3-byte sequence contains 4 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\e1\80\80\80"              ;; "\e1\80\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 3-byte sequence contains 2 bytes at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\e1\80"                    ;; "\e1\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 3-byte sequence contains 2 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e1\80\2e"                 ;; "\e1\80."
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 3-byte sequence contains 1 byte at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\e1"                       ;; "\e1"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 3-byte sequence contains 1 byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\e1\2e"                    ;; "\e1."
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 3-byte sequence contents
+
+;; first byte after (0xe0) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e0\00\a0"                 ;; "\e0\00\a0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xe0) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e0\7f\a0"                 ;; "\e0\7f\a0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; overlong encoding after 0xe0 prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e0\80\80"                 ;; "\e0\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; overlong encoding after 0xe0 prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e0\80\a0"                 ;; "\e0\80\a0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; overlong encoding after 0xe0 prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e0\9f\a0"                 ;; "\e0\9f\a0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; overlong encoding after 0xe0 prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e0\9f\bf"                 ;; "\e0\9f\bf"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xe0) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e0\c0\a0"                 ;; "\e0\c0\a0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xe0) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e0\fd\a0"                 ;; "\e0\fd\a0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (first normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e1\00\80"                 ;; "\e1\00\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (first normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e1\7f\80"                 ;; "\e1\7f\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (first normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e1\c0\80"                 ;; "\e1\c0\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (first normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e1\fd\80"                 ;; "\e1\fd\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ec\00\80"                 ;; "\ec\00\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ec\7f\80"                 ;; "\ec\7f\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ec\c0\80"                 ;; "\ec\c0\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ec\fd\80"                 ;; "\ec\fd\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xed) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ed\00\80"                 ;; "\ed\00\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xed) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ed\7f\80"                 ;; "\ed\7f\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; byte sequence reserved for UTF-16 surrogate half
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ed\a0\80"                 ;; "\ed\a0\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; byte sequence reserved for UTF-16 surrogate half
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ed\a0\bf"                 ;; "\ed\a0\bf"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; byte sequence reserved for UTF-16 surrogate half
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ed\bf\80"                 ;; "\ed\bf\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; byte sequence reserved for UTF-16 surrogate half
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ed\bf\bf"                 ;; "\ed\bf\bf"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xed) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ed\c0\80"                 ;; "\ed\c0\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xed) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ed\fd\80"                 ;; "\ed\fd\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ee\00\80"                 ;; "\ee\00\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ee\7f\80"                 ;; "\ee\7f\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ee\c0\80"                 ;; "\ee\c0\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ee\fd\80"                 ;; "\ee\fd\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (last normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ef\00\80"                 ;; "\ef\00\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (last normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ef\7f\80"                 ;; "\ef\7f\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (last normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ef\c0\80"                 ;; "\ef\c0\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (last normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ef\fd\80"                 ;; "\ef\fd\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 3-byte sequence contents (third byte)
+
+;; second byte after (0xe0) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e0\a0\00"                 ;; "\e0\a0\00"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xe0) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e0\a0\7f"                 ;; "\e0\a0\7f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xe0) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e0\a0\c0"                 ;; "\e0\a0\c0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xe0) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e0\a0\fd"                 ;; "\e0\a0\fd"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (first normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e1\80\00"                 ;; "\e1\80\00"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (first normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e1\80\7f"                 ;; "\e1\80\7f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (first normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e1\80\c0"                 ;; "\e1\80\c0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (first normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\e1\80\fd"                 ;; "\e1\80\fd"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ec\80\00"                 ;; "\ec\80\00"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ec\80\7f"                 ;; "\ec\80\7f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ec\80\c0"                 ;; "\ec\80\c0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ec\80\fd"                 ;; "\ec\80\fd"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xed) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ed\80\00"                 ;; "\ed\80\00"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xed) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ed\80\7f"                 ;; "\ed\80\7f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xed) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ed\80\c0"                 ;; "\ed\80\c0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xed) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ed\80\fd"                 ;; "\ed\80\fd"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ee\80\00"                 ;; "\ee\80\00"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ee\80\7f"                 ;; "\ee\80\7f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ee\80\c0"                 ;; "\ee\80\c0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ee\80\fd"                 ;; "\ee\80\fd"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (last normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ef\80\00"                 ;; "\ef\80\00"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (last normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ef\80\7f"                 ;; "\ef\80\7f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (last normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ef\80\c0"                 ;; "\ef\80\c0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (last normal) 3-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\ef\80\fd"                 ;; "\ef\80\fd"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 4-byte sequences
+
+;; 4-byte sequence contains 5 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\06"                       ;; custom section
+    "\05\f1\80\80\80\80"           ;; "\f1\80\80\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 4-byte sequence contains 3 bytes at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\f1\80\80"                 ;; "\f1\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 4-byte sequence contains 3 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\80\80\23"              ;; "\f1\80\80#"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 4-byte sequence contains 2 bytes at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\f1\80"                    ;; "\f1\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 4-byte sequence contains 2 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\f1\80\23"                 ;; "\f1\80#"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 4-byte sequence contains 1 byte at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\f1"                       ;; "\f1"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 4-byte sequence contains 1 byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\f1\23"                    ;; "\f1#"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 4-byte sequence contents
+
+;; first byte after (0xf0) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\00\90\90"              ;; "\f0\00\90\90"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xf0) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\7f\90\90"              ;; "\f0\7f\90\90"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; overlong encoding after 0xf0 prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\80\80\80"              ;; "\f0\80\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; overlong encoding after 0xf0 prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\80\90\90"              ;; "\f0\80\90\90"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; overlong encoding after 0xf0 prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\8f\90\90"              ;; "\f0\8f\90\90"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; overlong encoding after 0xf0 prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\8f\bf\bf"              ;; "\f0\8f\bf\bf"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xf0) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\c0\90\90"              ;; "\f0\c0\90\90"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xf0) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\fd\90\90"              ;; "\f0\fd\90\90"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (first normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\00\80\80"              ;; "\f1\00\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (first normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\7f\80\80"              ;; "\f1\7f\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (first normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\c0\80\80"              ;; "\f1\c0\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (first normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\fd\80\80"              ;; "\f1\fd\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (last normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f3\00\80\80"              ;; "\f3\00\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (last normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f3\7f\80\80"              ;; "\f3\7f\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (last normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f3\c0\80\80"              ;; "\f3\c0\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (last normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f3\fd\80\80"              ;; "\f3\fd\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xf4) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\00\80\80"              ;; "\f4\00\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xf4) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\7f\80\80"              ;; "\f4\7f\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; (first) invalid code point
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\90\80\80"              ;; "\f4\90\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; invalid code point
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\bf\80\80"              ;; "\f4\bf\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xf4) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\c0\80\80"              ;; "\f4\c0\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; first byte after (0xf4) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\fd\80\80"              ;; "\f4\fd\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; (first) invalid 4-byte prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f5\80\80\80"              ;; "\f5\80\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; (last) invalid 4-byte prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f7\80\80\80"              ;; "\f7\80\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; (last) invalid 4-byte prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f7\bf\bf\bf"              ;; "\f7\bf\bf\bf"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 4-byte sequence contents (third byte)
+
+;; second byte after (0xf0) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\90\00\90"              ;; "\f0\90\00\90"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xf0) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\90\7f\90"              ;; "\f0\90\7f\90"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xf0) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\90\c0\90"              ;; "\f0\90\c0\90"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xf0) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\90\fd\90"              ;; "\f0\90\fd\90"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (first normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\80\00\80"              ;; "\f1\80\00\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (first normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\80\7f\80"              ;; "\f1\80\7f\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (first normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\80\c0\80"              ;; "\f1\80\c0\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (first normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\80\fd\80"              ;; "\f1\80\fd\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (last normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f3\80\00\80"              ;; "\f3\80\00\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (last normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f3\80\7f\80"              ;; "\f3\80\7f\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (last normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f3\80\c0\80"              ;; "\f3\80\c0\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (last normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f3\80\fd\80"              ;; "\f3\80\fd\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xf4) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\80\00\80"              ;; "\f4\80\00\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xf4) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\80\7f\80"              ;; "\f4\80\7f\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xf4) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\80\c0\80"              ;; "\f4\80\c0\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; second byte after (0xf4) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\80\fd\80"              ;; "\f4\80\fd\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 4-byte sequence contents (fourth byte)
+
+;; third byte after (0xf0) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\90\90\00"              ;; "\f0\90\90\00"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (0xf0) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\90\90\7f"              ;; "\f0\90\90\7f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (0xf0) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\90\90\c0"              ;; "\f0\90\90\c0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (0xf0) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f0\90\90\fd"              ;; "\f0\90\90\fd"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (first normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\80\80\00"              ;; "\f1\80\80\00"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (first normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\80\80\7f"              ;; "\f1\80\80\7f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (first normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\80\80\c0"              ;; "\f1\80\80\c0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (first normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f1\80\80\fd"              ;; "\f1\80\80\fd"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (last normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f3\80\80\00"              ;; "\f3\80\80\00"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (last normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f3\80\80\7f"              ;; "\f3\80\80\7f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (last normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f3\80\80\c0"              ;; "\f3\80\80\c0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (last normal) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f3\80\80\fd"              ;; "\f3\80\80\fd"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (0xf4) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\80\80\00"              ;; "\f4\80\80\00"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (0xf4) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\80\80\7f"              ;; "\f4\80\80\7f"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (0xf4) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\80\80\c0"              ;; "\f4\80\80\c0"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; third byte after (0xf4) 4-byte prefix not a continuation byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f4\80\80\fd"              ;; "\f4\80\80\fd"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 5-byte sequences
+
+;; 5-byte sequence contains 6 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\07"                       ;; custom section
+    "\06\f8\80\80\80\80\80"        ;; "\f8\80\80\80\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 5-byte sequence contains 4 bytes at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f8\80\80\80"              ;; "\f8\80\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 5-byte sequence contains 4 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\06"                       ;; custom section
+    "\05\f8\80\80\80\23"           ;; "\f8\80\80\80#"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 5-byte sequence contains 3 bytes at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\f8\80\80"                 ;; "\f8\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 5-byte sequence contains 3 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\f8\80\80\23"              ;; "\f8\80\80#"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 5-byte sequence contains 2 bytes at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\f8\80"                    ;; "\f8\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 5-byte sequence contains 2 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\f8\80\23"                 ;; "\f8\80#"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 5-byte sequence contains 1 byte at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\f8"                       ;; "\f8"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 5-byte sequence contains 1 byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\f8\23"                    ;; "\f8#"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 5-byte sequence contents
+
+;; (first) invalid 5-byte prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\06"                       ;; custom section
+    "\05\f8\80\80\80\80"           ;; "\f8\80\80\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; (last) invalid 5-byte prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\06"                       ;; custom section
+    "\05\fb\bf\bf\bf\bf"           ;; "\fb\bf\bf\bf\bf"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 6-byte sequences
+
+;; 6-byte sequence contains 7 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\08"                       ;; custom section
+    "\07\fc\80\80\80\80\80\80"     ;; "\fc\80\80\80\80\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 6-byte sequence contains 5 bytes at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\06"                       ;; custom section
+    "\05\fc\80\80\80\80"           ;; "\fc\80\80\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 6-byte sequence contains 5 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\07"                       ;; custom section
+    "\06\fc\80\80\80\80\23"        ;; "\fc\80\80\80\80#"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 6-byte sequence contains 4 bytes at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\fc\80\80\80"              ;; "\fc\80\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 6-byte sequence contains 4 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\06"                       ;; custom section
+    "\05\fc\80\80\80\23"           ;; "\fc\80\80\80#"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 6-byte sequence contains 3 bytes at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\fc\80\80"                 ;; "\fc\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 6-byte sequence contains 3 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\fc\80\80\23"              ;; "\fc\80\80#"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 6-byte sequence contains 2 bytes at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\fc\80"                    ;; "\fc\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 6-byte sequence contains 2 bytes
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\04"                       ;; custom section
+    "\03\fc\80\23"                 ;; "\fc\80#"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 6-byte sequence contains 1 byte at end of string
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\fc"                       ;; "\fc"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; 6-byte sequence contains 1 byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\fc\23"                    ;; "\fc#"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; 6-byte sequence contents
+
+;; (first) invalid 6-byte prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\07"                       ;; custom section
+    "\06\fc\80\80\80\80\80"        ;; "\fc\80\80\80\80\80"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; (last) invalid 6-byte prefix
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\07"                       ;; custom section
+    "\06\fd\bf\bf\bf\bf\bf"        ;; "\fd\bf\bf\bf\bf\bf"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;;;; Miscellaneous invalid bytes
+
+;; invalid byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\fe"                       ;; "\fe"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; invalid byte
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\02"                       ;; custom section
+    "\01\ff"                       ;; "\ff"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; UTF-16BE BOM
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\fe\ff"                    ;; "\fe\ff"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; UTF-32BE BOM
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\00\00\fe\ff"              ;; "\00\00\fe\ff"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; UTF-16LE BOM
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\03"                       ;; custom section
+    "\02\ff\fe"                    ;; "\ff\fe"
+  )
+  "invalid UTF-8 encoding"
+)
+
+;; UTF-32LE BOM
+(assert_malformed
+  (module binary
+    "\00asm" "\01\00\00\00"
+    "\00\05"                       ;; custom section
+    "\04\ff\fe\00\00"              ;; "\ff\fe\00\00"
+  )
+  "invalid UTF-8 encoding"
+)
+