Merge pull request #3620 from facebook/errata_128k

[doc] add decoder errata paragraph

Author: Cyan4973

doc/decompressor_errata.md

@@ -6,12 +6,32 @@ Each entry will contain:
 1. The last affected decompressor versions.
 2. The decompressor components affected.
 2. Whether the compressed frame could ever be produced by the reference compressor.
-3. An example frame.
+3. An example frame (hexadecimal string when it can be short enough, link to golden file otherwise)
 4. A description of the bug.
 
 The document is in reverse chronological order, with the bugs that affect the most recent zstd decompressor versions listed first.
 
 
+Compressed block with a size of exactly 128 KB
+------------------------------------------------
+
+**Last affected version**: v1.5.2
+
+**Affected decompressor component(s)**: Library & CLI
+
+**Produced by the reference compressor**: No
+
+**Example Frame**: see zstd/tests/golden-decompression/block-128k.zst
+
+The zstd decoder incorrectly rejected blocks of type `Compressed_Block` when their size was exactly 128 KB.
+Note that `128 KB - 1` was accepted, and `128 KB + 1` is forbidden by the spec.
+
+This type of block was never generated by the reference compressor.
+
+These blocks used to be disallowed by the spec up until spec version 0.3.2 when the restriction was lifted by [PR#1689](https://github.com/facebook/zstd/pull/1689).
+
+> A Compressed_Block has the extra restriction that Block_Size is always strictly less than the decompressed size. If this condition cannot be respected, the block must be sent uncompressed instead (Raw_Block).
+
 Compressed block with 0 literals and 0 sequences
 ------------------------------------------------
 

doc/educational_decoder/zstd_decompress.c

@@ -1399,7 +1399,7 @@ size_t ZSTD_get_decompressed_size(const void *src, const size_t src_len) {
 /******* END OUTPUT SIZE COUNTING *********************************************/
 
 /******* DICTIONARY PARSING ***************************************************/
-dictionary_t* create_dictionary() {
+dictionary_t* create_dictionary(void) {
     dictionary_t* const dict = calloc(1, sizeof(dictionary_t));
     if (!dict) {
         BAD_ALLOC();