We include character-encoding validation.

Makefile

@@ -9,7 +9,7 @@
 CXXFLAGS =  -std=c++11 -g2 -O3 -march=native -Wall -Wextra -Wshadow -Iinclude  -Ibenchmark/linux  -Idependencies/rapidjson/include -Idependencies/sajson/include
 EXECUTABLES=parse jsoncheck numberparsingcheck minifiercompetition parsingcompetition minify allparserscheckfile
 
-HEADERS= include/jsonparser/stringparsing.h include/jsonparser/numberparsing.h include/jsonparser/jsonparser.h include/jsonparser/common_defs.h include/jsonparser/jsonioutil.h benchmark/benchmark.h benchmark/linux/linux-perf-events.h include/jsonparser/simdjson_internal.h include/jsonparser/stage1_find_marks.h include/jsonparser/stage2_flatten.h include/jsonparser/stage34_unified.h
+HEADERS= include/jsonparser/simdutf8check.h include/jsonparser/stringparsing.h include/jsonparser/numberparsing.h include/jsonparser/jsonparser.h include/jsonparser/common_defs.h include/jsonparser/jsonioutil.h benchmark/benchmark.h benchmark/linux/linux-perf-events.h include/jsonparser/simdjson_internal.h include/jsonparser/stage1_find_marks.h include/jsonparser/stage2_flatten.h include/jsonparser/stage34_unified.h
 LIBFILES=src/jsonioutil.cpp src/jsonparser.cpp src/stage1_find_marks.cpp     src/stage2_flatten.cpp        src/stage34_unified.cpp
 MINIFIERHEADERS=include/jsonparser/jsonminifier.h include/jsonparser/simdprune_tables.h
 MINIFIERLIBFILES=src/jsonminifier.cpp

include/jsonparser/common_defs.h

@@ -32,6 +32,7 @@ typedef __m256i m256;
 #define never_inline inline __attribute__((noinline, unused))
 
 #define UNUSED __attribute__((unused))
+#define WARN_UNUSED __attribute__((warn_unused_result))
 
 #ifndef likely
 #define likely(x) __builtin_expect(!!(x), 1)

include/jsonparser/simdutf8check.h

@@ -0,0 +1,385 @@
+
+#ifndef SIMDUTF8CHECK_H
+#define SIMDUTF8CHECK_H
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <x86intrin.h>
+/*
+ * legal utf-8 byte sequence
+ * http://www.unicode.org/versions/Unicode6.0.0/ch03.pdf - page 94
+ *
+ *  Code Points        1st       2s       3s       4s
+ * U+0000..U+007F     00..7F
+ * U+0080..U+07FF     C2..DF   80..BF
+ * U+0800..U+0FFF     E0       A0..BF   80..BF
+ * U+1000..U+CFFF     E1..EC   80..BF   80..BF
+ * U+D000..U+D7FF     ED       80..9F   80..BF
+ * U+E000..U+FFFF     EE..EF   80..BF   80..BF
+ * U+10000..U+3FFFF   F0       90..BF   80..BF   80..BF
+ * U+40000..U+FFFFF   F1..F3   80..BF   80..BF   80..BF
+ * U+100000..U+10FFFF F4       80..8F   80..BF   80..BF
+ *
+ */
+
+// all byte values must be no larger than 0xF4
+static inline void checkSmallerThan0xF4(__m128i current_bytes,
+                                        __m128i *has_error) {
+  // unsigned, saturates to 0 below max
+  *has_error = _mm_or_si128(*has_error,
+                            _mm_subs_epu8(current_bytes, _mm_set1_epi8(0xF4)));
+}
+
+static inline __m128i continuationLengths(__m128i high_nibbles) {
+  return _mm_shuffle_epi8(
+      _mm_setr_epi8(1, 1, 1, 1, 1, 1, 1, 1, // 0xxx (ASCII)
+                    0, 0, 0, 0,             // 10xx (continuation)
+                    2, 2,                   // 110x
+                    3,                      // 1110
+                    4), // 1111, next should be 0 (not checked here)
+      high_nibbles);
+}
+
+static inline __m128i carryContinuations(__m128i initial_lengths,
+                                         __m128i previous_carries) {
+
+  __m128i right1 =
+      _mm_subs_epu8(_mm_alignr_epi8(initial_lengths, previous_carries, 16 - 1),
+                    _mm_set1_epi8(1));
+  __m128i sum = _mm_add_epi8(initial_lengths, right1);
+
+  __m128i right2 = _mm_subs_epu8(_mm_alignr_epi8(sum, previous_carries, 16 - 2),
+                                 _mm_set1_epi8(2));
+  return _mm_add_epi8(sum, right2);
+}
+
+static inline void checkContinuations(__m128i initial_lengths, __m128i carries,
+                                      __m128i *has_error) {
+
+  // overlap || underlap
+  // carry > length && length > 0 || !(carry > length) && !(length > 0)
+  // (carries > length) == (lengths > 0)
+  __m128i overunder =
+      _mm_cmpeq_epi8(_mm_cmpgt_epi8(carries, initial_lengths),
+                     _mm_cmpgt_epi8(initial_lengths, _mm_setzero_si128()));
+
+  *has_error = _mm_or_si128(*has_error, overunder);
+}
+
+// when 0xED is found, next byte must be no larger than 0x9F
+// when 0xF4 is found, next byte must be no larger than 0x8F
+// next byte must be continuation, ie sign bit is set, so signed < is ok
+static inline void checkFirstContinuationMax(__m128i current_bytes,
+                                             __m128i off1_current_bytes,
+                                             __m128i *has_error) {
+  __m128i maskED = _mm_cmpeq_epi8(off1_current_bytes, _mm_set1_epi8(0xED));
+  __m128i maskF4 = _mm_cmpeq_epi8(off1_current_bytes, _mm_set1_epi8(0xF4));
+
+  __m128i badfollowED =
+      _mm_and_si128(_mm_cmpgt_epi8(current_bytes, _mm_set1_epi8(0x9F)), maskED);
+  __m128i badfollowF4 =
+      _mm_and_si128(_mm_cmpgt_epi8(current_bytes, _mm_set1_epi8(0x8F)), maskF4);
+
+  *has_error = _mm_or_si128(*has_error, _mm_or_si128(badfollowED, badfollowF4));
+}
+
+// map off1_hibits => error condition
+// hibits     off1    cur
+// C       => < C2 && true
+// E       => < E1 && < A0
+// F       => < F1 && < 90
+// else      false && false
+static inline void checkOverlong(__m128i current_bytes,
+                                 __m128i off1_current_bytes, __m128i hibits,
+                                 __m128i previous_hibits, __m128i *has_error) {
+  __m128i off1_hibits = _mm_alignr_epi8(hibits, previous_hibits, 16 - 1);
+  __m128i initial_mins = _mm_shuffle_epi8(
+      _mm_setr_epi8(-128, -128, -128, -128, -128, -128, -128, -128, -128, -128,
+                    -128, -128, // 10xx => false
+                    0xC2, -128, // 110x
+                    0xE1,       // 1110
+                    0xF1),
+      off1_hibits);
+
+  __m128i initial_under = _mm_cmpgt_epi8(initial_mins, off1_current_bytes);
+
+  __m128i second_mins = _mm_shuffle_epi8(
+      _mm_setr_epi8(-128, -128, -128, -128, -128, -128, -128, -128, -128, -128,
+                    -128, -128, // 10xx => false
+                    127, 127,   // 110x => true
+                    0xA0,       // 1110
+                    0x90),
+      off1_hibits);
+  __m128i second_under = _mm_cmpgt_epi8(second_mins, current_bytes);
+  *has_error =
+      _mm_or_si128(*has_error, _mm_and_si128(initial_under, second_under));
+}
+
+struct processed_utf_bytes {
+  __m128i rawbytes;
+  __m128i high_nibbles;
+  __m128i carried_continuations;
+};
+
+static inline void count_nibbles(__m128i bytes,
+                                 struct processed_utf_bytes *answer) {
+  answer->rawbytes = bytes;
+  answer->high_nibbles =
+      _mm_and_si128(_mm_srli_epi16(bytes, 4), _mm_set1_epi8(0x0F));
+}
+
+// check whether the current bytes are valid UTF-8
+// at the end of the function, previous gets updated
+static struct processed_utf_bytes
+checkUTF8Bytes(__m128i current_bytes, struct processed_utf_bytes *previous,
+               __m128i *has_error) {
+  struct processed_utf_bytes pb;
+  count_nibbles(current_bytes, &pb);
+
+  checkSmallerThan0xF4(current_bytes, has_error);
+
+  __m128i initial_lengths = continuationLengths(pb.high_nibbles);
+
+  pb.carried_continuations =
+      carryContinuations(initial_lengths, previous->carried_continuations);
+
+  checkContinuations(initial_lengths, pb.carried_continuations, has_error);
+
+  __m128i off1_current_bytes =
+      _mm_alignr_epi8(pb.rawbytes, previous->rawbytes, 16 - 1);
+  checkFirstContinuationMax(current_bytes, off1_current_bytes, has_error);
+
+  checkOverlong(current_bytes, off1_current_bytes, pb.high_nibbles,
+                previous->high_nibbles, has_error);
+  return pb;
+}
+
+static inline bool validate_utf8_fast(const char *src, size_t len) {
+  size_t i = 0;
+  __m128i has_error = _mm_setzero_si128();
+  struct processed_utf_bytes previous = {.rawbytes = _mm_setzero_si128(),
+                                         .high_nibbles = _mm_setzero_si128(),
+                                         .carried_continuations =
+                                             _mm_setzero_si128()};
+  if (len >= 16) {
+    for (; i <= len - 16; i += 16) {
+      __m128i current_bytes = _mm_loadu_si128((const __m128i *)(src + i));
+      previous = checkUTF8Bytes(current_bytes, &previous, &has_error);
+    }
+  }
+
+  // last part
+  if (i < len) {
+    char buffer[16];
+    memset(buffer, 0, 16);
+    memcpy(buffer, src + i, len - i);
+    __m128i current_bytes = _mm_loadu_si128((const __m128i *)(buffer));
+    previous = checkUTF8Bytes(current_bytes, &previous, &has_error);
+  } else {
+    has_error =
+        _mm_or_si128(_mm_cmpgt_epi8(previous.carried_continuations,
+                                    _mm_setr_epi8(9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+                                                  9, 9, 9, 9, 9, 1)),
+                     has_error);
+  }
+
+  return _mm_testz_si128(has_error, has_error);
+}
+
+#ifdef __AVX2__
+
+/*****************************/
+static inline __m256i push_last_byte_of_a_to_b(__m256i a, __m256i b) {
+  return _mm256_alignr_epi8(b, _mm256_permute2x128_si256(a, b, 0x21), 15);
+}
+
+static inline __m256i push_last_2bytes_of_a_to_b(__m256i a, __m256i b) {
+  return _mm256_alignr_epi8(b, _mm256_permute2x128_si256(a, b, 0x21), 14);
+}
+
+// all byte values must be no larger than 0xF4
+static inline void avxcheckSmallerThan0xF4(__m256i current_bytes,
+                                           __m256i *has_error) {
+  // unsigned, saturates to 0 below max
+  *has_error = _mm256_or_si256(
+      *has_error, _mm256_subs_epu8(current_bytes, _mm256_set1_epi8(0xF4)));
+}
+
+static inline __m256i avxcontinuationLengths(__m256i high_nibbles) {
+  return _mm256_shuffle_epi8(
+      _mm256_setr_epi8(1, 1, 1, 1, 1, 1, 1, 1, // 0xxx (ASCII)
+                       0, 0, 0, 0,             // 10xx (continuation)
+                       2, 2,                   // 110x
+                       3,                      // 1110
+                       4, // 1111, next should be 0 (not checked here)
+                       1, 1, 1, 1, 1, 1, 1, 1, // 0xxx (ASCII)
+                       0, 0, 0, 0,             // 10xx (continuation)
+                       2, 2,                   // 110x
+                       3,                      // 1110
+                       4 // 1111, next should be 0 (not checked here)
+                       ),
+      high_nibbles);
+}
+
+static inline __m256i avxcarryContinuations(__m256i initial_lengths,
+                                            __m256i previous_carries) {
+
+  __m256i right1 = _mm256_subs_epu8(
+      push_last_byte_of_a_to_b(previous_carries, initial_lengths),
+      _mm256_set1_epi8(1));
+  __m256i sum = _mm256_add_epi8(initial_lengths, right1);
+
+  __m256i right2 = _mm256_subs_epu8(
+      push_last_2bytes_of_a_to_b(previous_carries, sum), _mm256_set1_epi8(2));
+  return _mm256_add_epi8(sum, right2);
+}
+
+static inline void avxcheckContinuations(__m256i initial_lengths,
+                                         __m256i carries, __m256i *has_error) {
+
+  // overlap || underlap
+  // carry > length && length > 0 || !(carry > length) && !(length > 0)
+  // (carries > length) == (lengths > 0)
+  __m256i overunder = _mm256_cmpeq_epi8(
+      _mm256_cmpgt_epi8(carries, initial_lengths),
+      _mm256_cmpgt_epi8(initial_lengths, _mm256_setzero_si256()));
+
+  *has_error = _mm256_or_si256(*has_error, overunder);
+}
+
+// when 0xED is found, next byte must be no larger than 0x9F
+// when 0xF4 is found, next byte must be no larger than 0x8F
+// next byte must be continuation, ie sign bit is set, so signed < is ok
+static inline void avxcheckFirstContinuationMax(__m256i current_bytes,
+                                                __m256i off1_current_bytes,
+                                                __m256i *has_error) {
+  __m256i maskED =
+      _mm256_cmpeq_epi8(off1_current_bytes, _mm256_set1_epi8(0xED));
+  __m256i maskF4 =
+      _mm256_cmpeq_epi8(off1_current_bytes, _mm256_set1_epi8(0xF4));
+
+  __m256i badfollowED = _mm256_and_si256(
+      _mm256_cmpgt_epi8(current_bytes, _mm256_set1_epi8(0x9F)), maskED);
+  __m256i badfollowF4 = _mm256_and_si256(
+      _mm256_cmpgt_epi8(current_bytes, _mm256_set1_epi8(0x8F)), maskF4);
+
+  *has_error =
+      _mm256_or_si256(*has_error, _mm256_or_si256(badfollowED, badfollowF4));
+}
+
+// map off1_hibits => error condition
+// hibits     off1    cur
+// C       => < C2 && true
+// E       => < E1 && < A0
+// F       => < F1 && < 90
+// else      false && false
+static inline void avxcheckOverlong(__m256i current_bytes,
+                                    __m256i off1_current_bytes, __m256i hibits,
+                                    __m256i previous_hibits,
+                                    __m256i *has_error) {
+  __m256i off1_hibits = push_last_byte_of_a_to_b(previous_hibits, hibits);
+  __m256i initial_mins = _mm256_shuffle_epi8(
+      _mm256_setr_epi8(-128, -128, -128, -128, -128, -128, -128, -128, -128,
+                       -128, -128, -128, // 10xx => false
+                       0xC2, -128,       // 110x
+                       0xE1,             // 1110
+                       0xF1, -128, -128, -128, -128, -128, -128, -128, -128,
+                       -128, -128, -128, -128, // 10xx => false
+                       0xC2, -128,             // 110x
+                       0xE1,                   // 1110
+                       0xF1),
+      off1_hibits);
+
+  __m256i initial_under = _mm256_cmpgt_epi8(initial_mins, off1_current_bytes);
+
+  __m256i second_mins = _mm256_shuffle_epi8(
+      _mm256_setr_epi8(-128, -128, -128, -128, -128, -128, -128, -128, -128,
+                       -128, -128, -128, // 10xx => false
+                       127, 127,         // 110x => true
+                       0xA0,             // 1110
+                       0x90, -128, -128, -128, -128, -128, -128, -128, -128,
+                       -128, -128, -128, -128, // 10xx => false
+                       127, 127,               // 110x => true
+                       0xA0,                   // 1110
+                       0x90),
+      off1_hibits);
+  __m256i second_under = _mm256_cmpgt_epi8(second_mins, current_bytes);
+  *has_error = _mm256_or_si256(*has_error,
+                               _mm256_and_si256(initial_under, second_under));
+}
+
+struct avx_processed_utf_bytes {
+  __m256i rawbytes;
+  __m256i high_nibbles;
+  __m256i carried_continuations;
+};
+
+static inline void avx_count_nibbles(__m256i bytes,
+                                     struct avx_processed_utf_bytes *answer) {
+  answer->rawbytes = bytes;
+  answer->high_nibbles =
+      _mm256_and_si256(_mm256_srli_epi16(bytes, 4), _mm256_set1_epi8(0x0F));
+}
+
+// check whether the current bytes are valid UTF-8
+// at the end of the function, previous gets updated
+static struct avx_processed_utf_bytes
+avxcheckUTF8Bytes(__m256i current_bytes,
+                  struct avx_processed_utf_bytes *previous,
+                  __m256i *has_error) {
+  struct avx_processed_utf_bytes pb;
+  avx_count_nibbles(current_bytes, &pb);
+
+  avxcheckSmallerThan0xF4(current_bytes, has_error);
+
+  __m256i initial_lengths = avxcontinuationLengths(pb.high_nibbles);
+
+  pb.carried_continuations =
+      avxcarryContinuations(initial_lengths, previous->carried_continuations);
+
+  avxcheckContinuations(initial_lengths, pb.carried_continuations, has_error);
+
+  __m256i off1_current_bytes =
+      push_last_byte_of_a_to_b(previous->rawbytes, pb.rawbytes);
+  avxcheckFirstContinuationMax(current_bytes, off1_current_bytes, has_error);
+
+  avxcheckOverlong(current_bytes, off1_current_bytes, pb.high_nibbles,
+                   previous->high_nibbles, has_error);
+  return pb;
+}
+
+static inline bool validate_utf8_fast_avx(const char *src, size_t len) {
+  size_t i = 0;
+  __m256i has_error = _mm256_setzero_si256();
+  struct avx_processed_utf_bytes previous = {
+      .rawbytes = _mm256_setzero_si256(),
+      .high_nibbles = _mm256_setzero_si256(),
+      .carried_continuations = _mm256_setzero_si256()};
+  if (len >= 32) {
+    for (; i <= len - 32; i += 32) {
+      __m256i current_bytes = _mm256_loadu_si256((const __m256i *)(src + i));
+      previous = avxcheckUTF8Bytes(current_bytes, &previous, &has_error);
+    }
+  }
+
+  // last part
+  if (i < len) {
+    char buffer[32];
+    memset(buffer, 0, 32);
+    memcpy(buffer, src + i, len - i);
+    __m256i current_bytes = _mm256_loadu_si256((const __m256i *)(buffer));
+    previous = avxcheckUTF8Bytes(current_bytes, &previous, &has_error);
+  } else {
+    has_error = _mm256_or_si256(
+        _mm256_cmpgt_epi8(previous.carried_continuations,
+                          _mm256_setr_epi8(9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+                                           9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+                                           9, 9, 9, 9, 9, 9, 9, 1)),
+        has_error);
+  }
+
+  return _mm256_testz_si256(has_error, has_error);
+}
+
+#endif // __AVX2__
+#endif

include/jsonparser/stage1_find_marks.h

@@ -3,4 +3,5 @@
 #include "common_defs.h"
 #include "simdjson_internal.h"
 
+WARN_UNUSED
 bool find_structural_bits(const u8 *buf, size_t len, ParsedJson &pj);

include/jsonparser/stage2_flatten.h

@@ -3,4 +3,5 @@
 #include "common_defs.h"
 #include "simdjson_internal.h"
 
+WARN_UNUSED
 bool flatten_indexes(size_t len, ParsedJson &pj);

include/jsonparser/stage34_unified.h

@@ -4,4 +4,6 @@
 #include "simdjson_internal.h"
 
 void init_state_machine();
+
+WARN_UNUSED
 bool unified_machine(const u8 *buf, size_t len, ParsedJson &pj);

src/stage1_find_marks.cpp

@@ -11,6 +11,14 @@
 #include "jsonparser/common_defs.h"
 #include "jsonparser/simdjson_internal.h"
 
+#define UTF8VALIDATE
+// It seems that many parsers do UTF-8 validation.
+// RapidJSON does not do it by default, but a flag
+// allows it. It appears that sajson might do utf-8
+// validation
+#ifdef UTF8VALIDATE
+#include "jsonparser/simdutf8check.h"
+#endif
 using namespace std;
 
 // a straightforward comparison of a mask against input. 5 uops; would be
@@ -24,12 +32,25 @@ really_inline u64 cmp_mask_against_input(m256 input_lo, m256 input_hi,
   return res_0 | (res_1 << 32);
 }
 
+WARN_UNUSED
 /*never_inline*/ bool find_structural_bits(const u8 *buf, size_t len,
                                            ParsedJson &pj) {
   if (len > 0xffffff) {
     cerr << "Currently only support JSON files < 16MB\n";
     return false;
   }
+#ifdef UTF8VALIDATE
+#define TRYASCIIFIRST // we try parsing it as ASCII and fall over to UTF-8 only as needed.
+#ifdef TRYASCIIFIRST
+  bool isasciisofar = true;
+#endif
+  __m256i has_error = _mm256_setzero_si256();
+  struct avx_processed_utf_bytes previous = {
+      .rawbytes = _mm256_setzero_si256(),
+      .high_nibbles = _mm256_setzero_si256(),
+      .carried_continuations = _mm256_setzero_si256()};
+ #endif
+
   // Useful constant masks
   const u64 even_bits = 0x5555555555555555ULL;
   const u64 odd_bits = ~even_bits;
@@ -62,7 +83,23 @@ really_inline u64 cmp_mask_against_input(m256 input_lo, m256 input_hi,
 #endif
     m256 input_lo = _mm256_load_si256((const m256 *)(buf + idx + 0));
     m256 input_hi = _mm256_load_si256((const m256 *)(buf + idx + 32));
-
+#ifdef UTF8VALIDATE
+#ifdef TRYASCIIFIRST
+    if(isasciisofar) {
+      m256 highbit = _mm256_set1_epi8(0x80);
+      if((_mm256_testz_si256(input_lo,highbit) & _mm256_testz_si256(input_hi,highbit)) != 1) {
+        isasciisofar = false;
+        previous = avxcheckUTF8Bytes(input_lo, &previous, &has_error);
+        previous = avxcheckUTF8Bytes(input_hi, &previous, &has_error);
+      }
+    } else {
+#endif // TRYASCIIFIRST
+    previous = avxcheckUTF8Bytes(input_lo, &previous, &has_error);
+    previous = avxcheckUTF8Bytes(input_hi, &previous, &has_error);
+#ifdef TRYASCIIFIRST
+   }
+#endif // TRYASCIIFIRST
+#endif
     ////////////////////////////////////////////////////////////////////////////////////////////
     //     Step 1: detect odd sequences of backslashes
     ////////////////////////////////////////////////////////////////////////////////////////////
@@ -218,5 +255,13 @@ really_inline u64 cmp_mask_against_input(m256 input_lo, m256 input_hi,
         "final structurals and pseudo structurals after close quote removal");
     *(u64 *)(pj.structurals + idx / 8) = structurals;
   }
+#ifdef UTF8VALIDATE
+#ifdef TRYASCIIFIRST
+  return isasciisofar || ((!isasciisofar) && (_mm256_testz_si256(has_error, has_error)));
+#else
+  return _mm256_testz_si256(has_error, has_error);
+#endif
+#else
   return true;
+#endif
 }

src/stage2_flatten.cpp

@@ -49,6 +49,7 @@
 // that's all; the type of character the offset points to will
 // tell us exactly what we need to know. Naive but straightforward
 // implementation
+WARN_UNUSED
 bool flatten_indexes(size_t len, ParsedJson &pj) {
   u32 *base_ptr = pj.structural_indexes;
   u32 base = 0;

src/stage34_unified.cpp

@@ -31,6 +31,7 @@
 
 using namespace std;
 
+WARN_UNUSED
 really_inline bool is_valid_true_atom(const u8 * loc) {
     u64 tv = *(const u64 *)"true    ";
     u64 mask4 = 0x00000000ffffffff;
@@ -42,6 +43,7 @@ really_inline bool is_valid_true_atom(const u8 * loc) {
     return error == 0;
 }
 
+WARN_UNUSED
 really_inline bool is_valid_false_atom(const u8 * loc) {
     u64 fv = *(const u64 *)"false   ";
     u64 mask5 = 0x000000ffffffffff;
@@ -53,6 +55,7 @@ really_inline bool is_valid_false_atom(const u8 * loc) {
     return error == 0;
 }
 
+WARN_UNUSED
 really_inline bool is_valid_null_atom(const u8 * loc) {
     u64 nv = *(const u64 *)"null    ";
     u64 mask4 = 0x00000000ffffffff;
@@ -64,6 +67,7 @@ really_inline bool is_valid_null_atom(const u8 * loc) {
     return error == 0;
 }
 
+WARN_UNUSED
 bool unified_machine(const u8 *buf, size_t len, ParsedJson &pj) {
     u32 i = 0;
     u32 idx;