diff --git a/tests/fuzz/Makefile b/tests/fuzz/Makefile
index dfb8f191..c7d221f3 100644
--- a/tests/fuzz/Makefile
+++ b/tests/fuzz/Makefile
@@ -7,28 +7,28 @@
 # in the COPYING file in the root directory of this source tree).
 # ################################################################
 
+# Optionally user defined flags
 CFLAGS ?= -O3
 CXXFLAGS ?= -O3
+CPPFLAGS ?=
+LDFLAGS ?=
+ARFLAGS ?=
+LIB_FUZZING_ENGINE ?= libregression.a
 
 ZSTDDIR = ../../lib
 PRGDIR = ../../programs
 
 FUZZ_CPPFLAGS := -I$(ZSTDDIR) -I$(ZSTDDIR)/common -I$(ZSTDDIR)/compress \
 	-I$(ZSTDDIR)/dictBuilder -I$(ZSTDDIR)/deprecated -I$(PRGDIR) \
-	-DZSTD_DEBUG=1 -DMEM_FORCE_MEMORY_ACCESS=0 \
-	-DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION $(CPPFLAGS)
-FUZZ_CFLAGS := -Wall -Wextra -Wcast-qual -Wcast-align -Wshadow \
+	$(CPPFLAGS)
+FUZZ_EXTRA_FLAGS := -Wall -Wextra -Wcast-qual -Wcast-align -Wshadow \
 	-Wstrict-aliasing=1 -Wswitch-enum -Wdeclaration-after-statement \
 	-Wstrict-prototypes -Wundef -Wformat-security \
 	-Wvla -Wformat=2 -Winit-self -Wfloat-equal -Wwrite-strings \
 	-Wredundant-decls \
-	-g -fno-omit-frame-pointer $(CFLAGS)
-FUZZ_CXXFLAGS := -Wall -Wextra -Wcast-qual -Wcast-align -Wshadow \
-	-Wstrict-aliasing=1 -Wswitch-enum \
-	-Wdeclaration-after-statement -Wstrict-prototypes -Wundef \
-	-Wformat-security -Wvla -Wformat=2 -Winit-self -Wfloat-equal \
-	-Wwrite-strings -Wredundant-decls \
-	-g -fno-omit-frame-pointer -std=c++11 $(CXXFLAGS)
+	-g -fno-omit-frame-pointer
+FUZZ_CFLAGS := $(FUZZ_EXTRA_FLAGS) $(CFLAGS)
+FUZZ_CXXFLAGS := $(FUZZ_EXTRA_FLAGS) -std=c++11 $(CXXFLAGS)
 FUZZ_LDFLAGS := $(LDFLAGS)
 FUZZ_ARFLAGS := $(ARFLAGS)
 FUZZ_TARGET_FLAGS = $(FUZZ_CPPFLAGS) $(FUZZ_CXXFLAGS) $(FUZZ_LDFLAGS)
@@ -40,9 +40,8 @@ ZSTDCOMP_FILES   := $(ZSTDDIR)/compress/*.c
 ZSTDDECOMP_FILES := $(ZSTDDIR)/decompress/*.c
 ZSTD_FILES       := $(ZSTDDECOMP_FILES) $(ZSTDCOMMON_FILES) $(ZSTDCOMP_FILES)
 
-ZSTD_OBJ  := $(patsubst %.c,%.o, $(wildcard $(ZSTD_FILES)))
+ZSTD_OBJ := $(patsubst %.c,%.o, $(wildcard $(ZSTD_FILES)))
 
-LIBFUZZER ?= -lFuzzer
 
 .PHONY: default all clean
 
@@ -51,50 +50,35 @@ default: all
 all: \
 	simple_round_trip \
 	stream_round_trip \
+	block_round_trip \
 	simple_decompress \
-	stream_decompress
+	stream_decompress \
+	block_decompress
 
 %.o: %.c
 	$(CC) $(FUZZ_CPPFLAGS) $(FUZZ_CFLAGS) $^ -c -o $@
 
 simple_round_trip: $(FUZZ_HEADERS) $(ZSTD_OBJ) simple_round_trip.o
-	$(CXX) $(FUZZ_TARGET_FLAGS) $(ZSTD_OBJ) simple_round_trip.o $(LIBFUZZER) -o $@
+	$(CXX) $(FUZZ_TARGET_FLAGS) $(ZSTD_OBJ) simple_round_trip.o $(LIB_FUZZING_ENGINE) -o $@
 
 stream_round_trip: $(FUZZ_HEADERS) $(ZSTD_OBJ) stream_round_trip.o
-	$(CXX) $(FUZZ_TARGET_FLAGS) $(ZSTD_OBJ) stream_round_trip.o $(LIBFUZZER) -o $@
+	$(CXX) $(FUZZ_TARGET_FLAGS) $(ZSTD_OBJ) stream_round_trip.o $(LIB_FUZZING_ENGINE) -o $@
+
+block_round_trip: $(FUZZ_HEADERS) $(ZSTD_OBJ) block_round_trip.o
+	$(CXX) $(FUZZ_TARGET_FLAGS) $(ZSTD_OBJ) block_round_trip.o $(LIB_FUZZING_ENGINE) -o $@
 
 simple_decompress: $(FUZZ_HEADERS) $(ZSTD_OBJ) simple_decompress.o
-	$(CXX) $(FUZZ_TARGET_FLAGS) $(ZSTD_OBJ) simple_decompress.o $(LIBFUZZER) -o $@
+	$(CXX) $(FUZZ_TARGET_FLAGS) $(ZSTD_OBJ) simple_decompress.o $(LIB_FUZZING_ENGINE) -o $@
 
 stream_decompress: $(FUZZ_HEADERS) $(ZSTD_OBJ) stream_decompress.o
-	$(CXX) $(FUZZ_TARGET_FLAGS) $(ZSTD_OBJ) stream_decompress.o $(LIBFUZZER) -o $@
+	$(CXX) $(FUZZ_TARGET_FLAGS) $(ZSTD_OBJ) stream_decompress.o $(LIB_FUZZING_ENGINE) -o $@
+
+block_decompress: $(FUZZ_HEADERS) $(ZSTD_OBJ) block_decompress.o
+	$(CXX) $(FUZZ_TARGET_FLAGS) $(ZSTD_OBJ) block_decompress.o $(LIB_FUZZING_ENGINE) -o $@
 
 libregression.a: $(FUZZ_HEADERS) $(PRGDIR)/util.h regression_driver.o
 	$(AR) $(FUZZ_ARFLAGS) $@ regression_driver.o
 
-%-regression: libregression.a
-	$(RM) $*
-	$(MAKE) $* LDFLAGS="$(FUZZ_LDFLAGS) -L." LIBFUZZER=-lregression
-
-%-regression-test: %-regression
-	./$* corpora/$*
-
-regression-test: \
-	simple_round_trip-regression-test \
-	stream_round_trip-regression-test \
-	simple_decompress-regression-test \
-	stream_decompress-regression-test
-
-%-msan: clean
-	$(MAKE) $* CFLAGS="-fsanitize=memory $(FUZZ_CFLAGS)" \
-		CXXFLAGS="-fsanitize=memory $(FUZZ_CXXFLAGS)"
-
-UASAN_FLAGS := -fsanitize=address,undefined -fno-sanitize-recover=undefined \
-	-fno-sanitize=pointer-overflow
-%-uasan: clean
-	$(MAKE) $* CFLAGS="$(FUZZ_CFLAGS) $(UASAN_FLAGS)" \
-		CXXFLAGS="$(FUZZ_CXXFLAGS) $(UASAN_FLAGS)"
-
 # Install libfuzzer (not usable for MSAN testing)
 # Provided for convienence. To use this library run make libFuzzer and
 # set LDFLAGS=-L.
@@ -102,7 +86,7 @@ UASAN_FLAGS := -fsanitize=address,undefined -fno-sanitize-recover=undefined \
 libFuzzer:
 	@$(RM) -rf Fuzzer
 	@git clone https://chromium.googlesource.com/chromium/llvm-project/llvm/lib/Fuzzer
-	@./Fuzzer/build.sh
+	@cd Fuzzer && ./build.sh
 
 clean:
 	@$(MAKE) -C $(ZSTDDIR) clean
diff --git a/tests/fuzz/README.md b/tests/fuzz/README.md
index 38a4f3d1..6d0fab55 100644
--- a/tests/fuzz/README.md
+++ b/tests/fuzz/README.md
@@ -2,33 +2,87 @@
 
 Each fuzzing target can be built with multiple engines.
 
+## fuzz.py
+
+`fuzz.py` is a helper script for building and running fuzzers.
+Run `./fuzz.py -h` for the commands and run `./fuzz.py COMMAND -h` for
+command specific help.
+
+### Generating Data
+
+`fuzz.py` provides a utility to generate seed data for each fuzzer.
+
+```
+make -C ../tests decodecorpus
+./fuzz.py gen TARGET
+```
+
+By default it outputs 100 samples, each at most 8KB into `corpora/TARGET-seed`,
+but that can be configured with the `--number`, `--max-size-log` and `--seed`
+flags.
+
+### Build
+It respects the usual build environment variables `CC`, `CFLAGS`, etc.
+The environment variables can be overridden with the corresponding flags
+`--cc`, `--cflags`, etc.
+The specific fuzzing engine is selected with `LIB_FUZZING_ENGINE` or
+`--lib-fuzzing-engine`, the default is `libregression.a`.
+It has flags that can easily set up sanitizers `--enable-{a,ub,m}san`, and
+coverage instrumentation `--enable-coverage`.
+It sets sane defaults which can be overriden with flags `--debug`,
+`--enable-ubsan-pointer-overlow`, etc.
+Run `./fuzz.py build -h` for help.
+
+### Running Fuzzers
+
+`./fuzz.py` can run `libfuzzer`, `afl`, and `regression` tests.
+See the help of the relevant command for options.
+Flags not parsed by `fuzz.py` are passed to the fuzzing engine.
+The command used to run the fuzzer is printed for debugging.
+
 ## LibFuzzer
 
-You can install `libFuzzer` with `make libFuzzer`. Then you can make each target
-with `make target LDFLAGS=-L. CC=clang CXX=clang++`.
+```
+# Build libfuzzer if necessary
+make libFuzzer
+# Build the fuzz targets
+./fuzz.py build all --enable-coverage --enable-asan --enable-ubsan --lib-fuzzing-engine Fuzzer/libFuzzer.a --cc clang --cxx clang++
+# OR equivalently
+CC=clang CXX=clang++ LIB_FUZZING_ENGINE=Fuzzer/libFuzzer.a ./fuzz.py build all --enable-coverage --enable-asan --enable-ubsan
+# Run the fuzzer
+./fuzz.py libfuzzer TARGET -max_len=8192 -jobs=4
+```
+
+where `TARGET` could be `simple_decompress`, `stream_round_trip`, etc.
+
+### MSAN
+
+Fuzzing with `libFuzzer` and `MSAN` will require building a C++ standard library
+and libFuzzer with MSAN.
+`fuzz.py` respects the environment variables / flags `MSAN_EXTRA_CPPFLAGS`,
+`MSAN_EXTRA_CFLAGS`, `MSAN_EXTRA_CXXFLAGS`, `MSAN_EXTRA_LDFLAGS` to easily pass
+the extra parameters only for MSAN.
 
 ## AFL
 
-The regression driver also serves as a binary for `afl-fuzz`. You can make each
-target with one of these commands:
+The default `LIB_FUZZING_ENGINE` is `libregression.a`, which produces a binary
+that AFL can use.
 
 ```
-make target-regression CC=afl-clang CXX=afl-clang++
-AFL_MSAN=1 make target-regression-msan CC=afl-clang CXX=afl-clang++
-AFL_ASAN=1 make target-regression-uasan CC=afl-clang CXX=afl-clang++
+# Build the fuzz targets
+CC=afl-clang CXX=afl-clang++ ./fuzz.py build all --enable-asan --enable-ubsan
+# Run the fuzzer without a memory limit because of ASAN
+./fuzz.py afl TARGET -m none
 ```
 
-Then run as `./target @@`.
-
 ## Regression Testing
 
-Each fuzz target has a corpus checked into the repo under `fuzz/corpora/`.
-You can run regression tests on the corpora to ensure that inputs which
-previously exposed bugs still pass. You can make these targets to run the
-regression tests with different sanitizers.
+The regression rest supports the `all` target to run all the fuzzers in one
+command.
 
 ```
-make regression-test
-make regression-test-msan
-make regression-test-uasan
+CC=clang CXX=clang++ ./fuzz.py build all --enable-asan --enable-ubsan
+./fuzz.py regression all
+CC=clang CXX=clang++ ./fuzz.py build all --enable-msan
+./fuzz.py regression all
 ```
diff --git a/tests/fuzz/block_decompress.c b/tests/fuzz/block_decompress.c
new file mode 100644
index 00000000..3cccc32f
--- /dev/null
+++ b/tests/fuzz/block_decompress.c
@@ -0,0 +1,51 @@
+/**
+ * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ */
+
+/**
+ * This fuzz target attempts to decompress the fuzzed data with the simple
+ * decompression function to ensure the decompressor never crashes.
+ */
+
+#define ZSTD_STATIC_LINKING_ONLY
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include "fuzz_helpers.h"
+#include "zstd.h"
+
+static ZSTD_DCtx *dctx = NULL;
+static void* rBuf = NULL;
+static size_t bufSize = 0;
+
+int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
+{
+    size_t const neededBufSize = ZSTD_BLOCKSIZE_MAX;
+
+    FUZZ_seed(&src, &size);
+
+    /* Allocate all buffers and contexts if not already allocated */
+    if (neededBufSize > bufSize) {
+        free(rBuf);
+        rBuf = malloc(neededBufSize);
+        bufSize = neededBufSize;
+        FUZZ_ASSERT(rBuf);
+    }
+    if (!dctx) {
+        dctx = ZSTD_createDCtx();
+        FUZZ_ASSERT(dctx);
+    }
+    ZSTD_decompressBegin(dctx);
+    ZSTD_decompressBlock(dctx, rBuf, neededBufSize, src, size);
+
+#ifndef STATEFUL_FUZZING
+    ZSTD_freeDCtx(dctx); dctx = NULL;
+#endif
+    return 0;
+}
diff --git a/tests/fuzz/block_round_trip.c b/tests/fuzz/block_round_trip.c
new file mode 100644
index 00000000..3b3f2ff6
--- /dev/null
+++ b/tests/fuzz/block_round_trip.c
@@ -0,0 +1,99 @@
+/**
+ * Copyright (c) 2016-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ */
+
+/**
+ * This fuzz target performs a zstd round-trip test (compress & decompress),
+ * compares the result with the original, and calls abort() on corruption.
+ */
+
+#define ZSTD_STATIC_LINKING_ONLY
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include "fuzz_helpers.h"
+#include "zstd.h"
+
+static const int kMaxClevel = 19;
+
+static ZSTD_CCtx *cctx = NULL;
+static ZSTD_DCtx *dctx = NULL;
+static void* cBuf = NULL;
+static void* rBuf = NULL;
+static size_t bufSize = 0;
+static uint32_t seed;
+
+static size_t roundTripTest(void *result, size_t resultCapacity,
+                            void *compressed, size_t compressedCapacity,
+                            const void *src, size_t srcSize)
+{
+  int const cLevel = FUZZ_rand(&seed) % kMaxClevel;
+  size_t ret = ZSTD_compressBegin(cctx, cLevel);
+
+  if (ZSTD_isError(ret)) {
+      fprintf(stderr, "ZSTD_compressBegin() error: %s\n",
+              ZSTD_getErrorName(ret));
+      return ret;
+  }
+
+  ret = ZSTD_compressBlock(cctx, compressed, compressedCapacity, src, srcSize);
+  if (ZSTD_isError(ret)) {
+    fprintf(stderr, "ZSTD_compressBlock() error: %s\n", ZSTD_getErrorName(ret));
+    return ret;
+  }
+  if (ret == 0) {
+        FUZZ_ASSERT(resultCapacity >= srcSize);
+        memcpy(result, src, srcSize);
+        return srcSize;
+  }
+  ZSTD_decompressBegin(dctx);
+  return ZSTD_decompressBlock(dctx, result, resultCapacity, compressed, ret);
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
+{
+    size_t neededBufSize;
+
+    seed = FUZZ_seed(&src, &size);
+    neededBufSize = size;
+    if (size > ZSTD_BLOCKSIZE_MAX)
+        return 0;
+
+    /* Allocate all buffers and contexts if not already allocated */
+    if (neededBufSize > bufSize || !cBuf || !rBuf) {
+        free(cBuf);
+        free(rBuf);
+        cBuf = malloc(neededBufSize);
+        rBuf = malloc(neededBufSize);
+        bufSize = neededBufSize;
+        FUZZ_ASSERT(cBuf && rBuf);
+    }
+    if (!cctx) {
+        cctx = ZSTD_createCCtx();
+        FUZZ_ASSERT(cctx);
+    }
+    if (!dctx) {
+        dctx = ZSTD_createDCtx();
+        FUZZ_ASSERT(dctx);
+    }
+
+    {
+        size_t const result =
+            roundTripTest(rBuf, neededBufSize, cBuf, neededBufSize, src, size);
+        FUZZ_ASSERT_MSG(!ZSTD_isError(result), ZSTD_getErrorName(result));
+        FUZZ_ASSERT_MSG(result == size, "Incorrect regenerated size");
+        FUZZ_ASSERT_MSG(!memcmp(src, rBuf, size), "Corruption!");
+    }
+#ifndef STATEFUL_FUZZING
+    ZSTD_freeCCtx(cctx); cctx = NULL;
+    ZSTD_freeDCtx(dctx); dctx = NULL;
+#endif
+    return 0;
+}
diff --git a/tests/fuzz/fuzz.h b/tests/fuzz/fuzz.h
index 3017db3a..a6484547 100644
--- a/tests/fuzz/fuzz.h
+++ b/tests/fuzz/fuzz.h
@@ -12,15 +12,17 @@
  * Fuzz targets have some common parameters passed as macros during compilation.
  * Check the documentation for each individual fuzzer for more parameters.
  *
- * @param STATEFULL_FUZZING:
+ * @param STATEFUL_FUZZING:
  *        Define this to reuse state between fuzzer runs. This can be useful to
  *        test code paths which are only executed when contexts are reused.
  *        WARNING: Makes reproducing crashes much harder.
  *        Default: Not defined.
  * @param FUZZ_RNG_SEED_SIZE:
  *        The number of bytes of the source to look at when constructing a seed
- *        for the deterministic RNG.
- *        Default: 128.
+ *        for the deterministic RNG. These bytes are discarded before passing
+ *        the data to zstd functions. Every fuzzer initializes the RNG exactly
+ *        once before doing anything else, even if it is unused.
+ *        Default: 4.
  * @param ZSTD_DEBUG:
  *        This is a parameter for the zstd library. Defining `ZSTD_DEBUG=1`
  *        enables assert() statements in the zstd library. Higher levels enable
@@ -41,12 +43,20 @@
 #define FUZZ_H
 
 #ifndef FUZZ_RNG_SEED_SIZE
-#  define FUZZ_RNG_SEED_SIZE 128
+#  define FUZZ_RNG_SEED_SIZE 4
 #endif
 
 #include <stddef.h>
 #include <stdint.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif
diff --git a/tests/fuzz/fuzz.py b/tests/fuzz/fuzz.py
new file mode 100755
index 00000000..0ce201cd
--- /dev/null
+++ b/tests/fuzz/fuzz.py
@@ -0,0 +1,721 @@
+#! /usr/bin/env python
+
+# ################################################################
+# Copyright (c) 2016-present, Facebook, Inc.
+# All rights reserved.
+#
+# This source code is licensed under both the BSD-style license (found in the
+# LICENSE file in the root directory of this source tree) and the GPLv2 (found
+# in the COPYING file in the root directory of this source tree).
+# ##########################################################################
+
+import argparse
+import contextlib
+import os
+import re
+import shutil
+import subprocess
+import sys
+import tempfile
+
+
+def abs_join(a, *p):
+    return os.path.abspath(os.path.join(a, *p))
+
+
+# Constants
+FUZZ_DIR = os.path.abspath(os.path.dirname(__file__))
+CORPORA_DIR = abs_join(FUZZ_DIR, 'corpora')
+TARGETS = [
+    'simple_round_trip',
+    'stream_round_trip',
+    'block_round_trip',
+    'simple_decompress',
+    'stream_decompress',
+    'block_decompress',
+]
+ALL_TARGETS = TARGETS + ['all']
+FUZZ_RNG_SEED_SIZE = 4
+
+# Standard environment variables
+CC = os.environ.get('CC', 'cc')
+CXX = os.environ.get('CXX', 'c++')
+CPPFLAGS = os.environ.get('CPPFLAGS', '')
+CFLAGS = os.environ.get('CFLAGS', '-O3')
+CXXFLAGS = os.environ.get('CXXFLAGS', CFLAGS)
+LDFLAGS = os.environ.get('LDFLAGS', '')
+MFLAGS = os.environ.get('MFLAGS', '-j')
+
+# Fuzzing environment variables
+LIB_FUZZING_ENGINE = os.environ.get('LIB_FUZZING_ENGINE', 'libregression.a')
+AFL_FUZZ = os.environ.get('AFL_FUZZ', 'afl-fuzz')
+DECODECORPUS = os.environ.get('DECODECORPUS',
+                              abs_join(FUZZ_DIR, '..', 'decodecorpus'))
+
+# Sanitizer environment variables
+MSAN_EXTRA_CPPFLAGS = os.environ.get('MSAN_EXTRA_CPPFLAGS', '')
+MSAN_EXTRA_CFLAGS = os.environ.get('MSAN_EXTRA_CFLAGS', '')
+MSAN_EXTRA_CXXFLAGS = os.environ.get('MSAN_EXTRA_CXXFLAGS', '')
+MSAN_EXTRA_LDFLAGS = os.environ.get('MSAN_EXTRA_LDFLAGS', '')
+
+
+def create(r):
+    d = os.path.abspath(r)
+    if not os.path.isdir(d):
+        os.mkdir(d)
+    return d
+
+
+def check(r):
+    d = os.path.abspath(r)
+    if not os.path.isdir(d):
+        return None
+    return d
+
+
+@contextlib.contextmanager
+def tmpdir():
+    dirpath = tempfile.mkdtemp()
+    try:
+        yield dirpath
+    finally:
+        shutil.rmtree(dirpath, ignore_errors=True)
+
+
+def parse_env_flags(args, flags):
+    """
+    Look for flags set by environment variables.
+    """
+    flags = ' '.join(flags)
+    san_flags = ','.join(re.findall('-fsanitize=((?:[a-z]+,?)+)', flags))
+    nosan_flags = ','.join(re.findall('-fno-sanitize=((?:[a-z]+,?)+)', flags))
+
+    def set_sanitizer(sanitizer, default, san, nosan):
+        if sanitizer in san and sanitizer in nosan:
+            raise RuntimeError('-fno-sanitize={s} and -fsanitize={s} passed'.
+                               format(s=sanitizer))
+        if sanitizer in san:
+            return True
+        if sanitizer in nosan:
+            return False
+        return default
+
+    san = set(san_flags.split(','))
+    nosan = set(nosan_flags.split(','))
+
+    args.asan = set_sanitizer('address', args.asan, san, nosan)
+    args.msan = set_sanitizer('memory', args.msan, san, nosan)
+    args.ubsan = set_sanitizer('undefined', args.ubsan, san, nosan)
+
+    args.sanitize = args.asan or args.msan or args.ubsan
+
+    return args
+
+
+def build_parser(args):
+    description = """
+    Cleans the repository and builds a fuzz target (or all).
+    Many flags default to environment variables (default says $X='y').
+    Options that aren't enabling features default to the correct values for
+    zstd.
+    Enable sanitizers with --enable-*san.
+    For regression testing just build.
+    For libFuzzer set LIB_FUZZING_ENGINE and pass --enable-coverage.
+    For AFL set CC and CXX to AFL's compilers and set
+    LIB_FUZZING_ENGINE='libregression.a'.
+    """
+    parser = argparse.ArgumentParser(prog=args.pop(0), description=description)
+    parser.add_argument(
+        '--lib-fuzzing-engine',
+        dest='lib_fuzzing_engine',
+        type=str,
+        default=LIB_FUZZING_ENGINE,
+        help=('The fuzzing engine to use e.g. /path/to/libFuzzer.a '
+              "(default: $LIB_FUZZING_ENGINE='{})".format(LIB_FUZZING_ENGINE)))
+    parser.add_argument(
+        '--enable-coverage',
+        dest='coverage',
+        action='store_true',
+        help='Enable coverage instrumentation (-fsanitize-coverage)')
+    parser.add_argument(
+        '--enable-asan', dest='asan', action='store_true', help='Enable UBSAN')
+    parser.add_argument(
+        '--enable-ubsan',
+        dest='ubsan',
+        action='store_true',
+        help='Enable UBSAN')
+    parser.add_argument(
+        '--enable-ubsan-pointer-overflow',
+        dest='ubsan_pointer_overflow',
+        action='store_true',
+        help='Enable UBSAN pointer overflow check (known failure)')
+    parser.add_argument(
+        '--enable-msan', dest='msan', action='store_true', help='Enable MSAN')
+    parser.add_argument(
+        '--enable-msan-track-origins', dest='msan_track_origins',
+        action='store_true', help='Enable MSAN origin tracking')
+    parser.add_argument(
+        '--msan-extra-cppflags',
+        dest='msan_extra_cppflags',
+        type=str,
+        default=MSAN_EXTRA_CPPFLAGS,
+        help="Extra CPPFLAGS for MSAN (default: $MSAN_EXTRA_CPPFLAGS='{}')".
+        format(MSAN_EXTRA_CPPFLAGS))
+    parser.add_argument(
+        '--msan-extra-cflags',
+        dest='msan_extra_cflags',
+        type=str,
+        default=MSAN_EXTRA_CFLAGS,
+        help="Extra CFLAGS for MSAN (default: $MSAN_EXTRA_CFLAGS='{}')".format(
+            MSAN_EXTRA_CFLAGS))
+    parser.add_argument(
+        '--msan-extra-cxxflags',
+        dest='msan_extra_cxxflags',
+        type=str,
+        default=MSAN_EXTRA_CXXFLAGS,
+        help="Extra CXXFLAGS for MSAN (default: $MSAN_EXTRA_CXXFLAGS='{}')".
+        format(MSAN_EXTRA_CXXFLAGS))
+    parser.add_argument(
+        '--msan-extra-ldflags',
+        dest='msan_extra_ldflags',
+        type=str,
+        default=MSAN_EXTRA_LDFLAGS,
+        help="Extra LDFLAGS for MSAN (default: $MSAN_EXTRA_LDFLAGS='{}')".
+        format(MSAN_EXTRA_LDFLAGS))
+    parser.add_argument(
+        '--enable-sanitize-recover',
+        dest='sanitize_recover',
+        action='store_true',
+        help='Non-fatal sanitizer errors where possible')
+    parser.add_argument(
+        '--debug',
+        dest='debug',
+        type=int,
+        default=1,
+        help='Set ZSTD_DEBUG (default: 1)')
+    parser.add_argument(
+        '--force-memory-access',
+        dest='memory_access',
+        type=int,
+        default=0,
+        help='Set MEM_FORCE_MEMORY_ACCESS (default: 0)')
+    parser.add_argument(
+        '--fuzz-rng-seed-size',
+        dest='fuzz_rng_seed_size',
+        type=int,
+        default=4,
+        help='Set FUZZ_RNG_SEED_SIZE (default: 4)')
+    parser.add_argument(
+        '--disable-fuzzing-mode',
+        dest='fuzzing_mode',
+        action='store_false',
+        help='Do not define FUZZING_BUILD_MORE_UNSAFE_FOR_PRODUCTION')
+    parser.add_argument(
+        '--enable-stateful-fuzzing',
+        dest='stateful_fuzzing',
+        action='store_true',
+        help='Reuse contexts between runs (makes reproduction impossible)')
+    parser.add_argument(
+        '--cc',
+        dest='cc',
+        type=str,
+        default=CC,
+        help="CC (default: $CC='{}')".format(CC))
+    parser.add_argument(
+        '--cxx',
+        dest='cxx',
+        type=str,
+        default=CXX,
+        help="CXX (default: $CXX='{}')".format(CXX))
+    parser.add_argument(
+        '--cppflags',
+        dest='cppflags',
+        type=str,
+        default=CPPFLAGS,
+        help="CPPFLAGS (default: $CPPFLAGS='{}')".format(CPPFLAGS))
+    parser.add_argument(
+        '--cflags',
+        dest='cflags',
+        type=str,
+        default=CFLAGS,
+        help="CFLAGS (default: $CFLAGS='{}')".format(CFLAGS))
+    parser.add_argument(
+        '--cxxflags',
+        dest='cxxflags',
+        type=str,
+        default=CXXFLAGS,
+        help="CXXFLAGS (default: $CXXFLAGS='{}')".format(CXXFLAGS))
+    parser.add_argument(
+        '--ldflags',
+        dest='ldflags',
+        type=str,
+        default=LDFLAGS,
+        help="LDFLAGS (default: $LDFLAGS='{}')".format(LDFLAGS))
+    parser.add_argument(
+        '--mflags',
+        dest='mflags',
+        type=str,
+        default=MFLAGS,
+        help="Extra Make flags (default: $MFLAGS='{}')".format(MFLAGS))
+    parser.add_argument(
+        'TARGET',
+        nargs='*',
+        type=str,
+        help='Fuzz target(s) to build {{{}}}'.format(', '.join(ALL_TARGETS))
+    )
+    args = parser.parse_args(args)
+    args = parse_env_flags(args, ' '.join(
+        [args.cppflags, args.cflags, args.cxxflags, args.ldflags]))
+
+    # Check option sanitiy
+    if args.msan and (args.asan or args.ubsan):
+        raise RuntimeError('MSAN may not be used with any other sanitizers')
+    if args.msan_track_origins and not args.msan:
+        raise RuntimeError('--enable-msan-track-origins requires MSAN')
+    if args.ubsan_pointer_overflow and not args.ubsan:
+        raise RuntimeError('--enable-ubsan-pointer-overlow requires UBSAN')
+    if args.sanitize_recover and not args.sanitize:
+        raise RuntimeError('--enable-sanitize-recover but no sanitizers used')
+
+    return args
+
+
+def build(args):
+    try:
+        args = build_parser(args)
+    except Exception as e:
+        print(e)
+        return 1
+    # The compilation flags we are setting
+    targets = args.TARGET
+    cc = args.cc
+    cxx = args.cxx
+    cppflags = [args.cppflags]
+    cflags = [args.cflags]
+    ldflags = [args.ldflags]
+    cxxflags = [args.cxxflags]
+    mflags = [args.mflags] if args.mflags else []
+    # Flags to be added to both cflags and cxxflags
+    common_flags = []
+
+    cppflags += [
+        '-DZSTD_DEBUG={}'.format(args.debug),
+        '-DMEM_FORCE_MEMORY_ACCESS={}'.format(args.memory_access),
+        '-DFUZZ_RNG_SEED_SIZE={}'.format(args.fuzz_rng_seed_size),
+    ]
+
+    mflags += ['LIB_FUZZING_ENGINE={}'.format(args.lib_fuzzing_engine)]
+
+    # Set flags for options
+    if args.coverage:
+        common_flags += [
+            '-fsanitize-coverage=trace-pc-guard,indirect-calls,trace-cmp'
+        ]
+
+    if args.sanitize_recover:
+        recover_flags = ['-fsanitize-recover=all']
+    else:
+        recover_flags = ['-fno-sanitize-recover=all']
+    if args.sanitize:
+        common_flags += recover_flags
+
+    if args.msan:
+        msan_flags = ['-fsanitize=memory']
+        if args.msan_track_origins:
+            msan_flags += ['-fsanitize-memory-track-origins']
+        common_flags += msan_flags
+        # Append extra MSAN flags (it might require special setup)
+        cppflags += [args.msan_extra_cppflags]
+        cflags += [args.msan_extra_cflags]
+        cxxflags += [args.msan_extra_cxxflags]
+        ldflags += [args.msan_extra_ldflags]
+
+    if args.asan:
+        common_flags += ['-fsanitize=address']
+
+    if args.ubsan:
+        ubsan_flags = ['-fsanitize=undefined']
+        if not args.ubsan_pointer_overflow:
+            ubsan_flags += ['-fno-sanitize=pointer-overflow']
+        common_flags += ubsan_flags
+
+    if args.stateful_fuzzing:
+        cppflags += ['-DSTATEFUL_FUZZING']
+
+    if args.fuzzing_mode:
+        cppflags += ['-DFUZZING_BUILD_MORE_UNSAFE_FOR_PRODUCTION']
+
+    if args.lib_fuzzing_engine == 'libregression.a':
+        targets = ['libregression.a'] + targets
+
+    # Append the common flags
+    cflags += common_flags
+    cxxflags += common_flags
+
+    # Prepare the flags for Make
+    cc_str = "CC={}".format(cc)
+    cxx_str = "CXX={}".format(cxx)
+    cppflags_str = "CPPFLAGS={}".format(' '.join(cppflags))
+    cflags_str = "CFLAGS={}".format(' '.join(cflags))
+    cxxflags_str = "CXXFLAGS={}".format(' '.join(cxxflags))
+    ldflags_str = "LDFLAGS={}".format(' '.join(ldflags))
+
+    # Print the flags
+    print('MFLAGS={}'.format(' '.join(mflags)))
+    print(cc_str)
+    print(cxx_str)
+    print(cppflags_str)
+    print(cflags_str)
+    print(cxxflags_str)
+    print(ldflags_str)
+
+    # Clean and build
+    clean_cmd = ['make', 'clean'] + mflags
+    print(' '.join(clean_cmd))
+    subprocess.check_call(clean_cmd)
+    build_cmd = [
+        'make',
+        cc_str,
+        cxx_str,
+        cppflags_str,
+        cflags_str,
+        cxxflags_str,
+        ldflags_str,
+    ] + mflags + targets
+    print(' '.join(build_cmd))
+    subprocess.check_call(build_cmd)
+    return 0
+
+
+def libfuzzer_parser(args):
+    description = """
+    Runs a libfuzzer binary.
+    Passes all extra arguments to libfuzzer.
+    The fuzzer should have been build with LIB_FUZZING_ENGINE pointing to
+    libFuzzer.a.
+    Generates output in the CORPORA directory, puts crashes in the ARTIFACT
+    directory, and takes extra input from the SEED directory.
+    To merge AFL's output pass the SEED as AFL's output directory and pass
+    '-merge=1'.
+    """
+    parser = argparse.ArgumentParser(prog=args.pop(0), description=description)
+    parser.add_argument(
+        '--corpora',
+        type=str,
+        help='Override the default corpora dir (default: {})'.format(
+            abs_join(CORPORA_DIR, 'TARGET')))
+    parser.add_argument(
+        '--artifact',
+        type=str,
+        help='Override the default artifact dir (default: {})'.format(
+            abs_join(CORPORA_DIR, 'TARGET-crash')))
+    parser.add_argument(
+        '--seed',
+        type=str,
+        help='Override the default seed dir (default: {})'.format(
+            abs_join(CORPORA_DIR, 'TARGET-seed')))
+    parser.add_argument(
+        'TARGET',
+        type=str,
+        help='Fuzz target(s) to build {{{}}}'.format(', '.join(TARGETS)))
+    args, extra = parser.parse_known_args(args)
+    args.extra = extra
+
+    if args.TARGET and args.TARGET not in TARGETS:
+        raise RuntimeError('{} is not a valid target'.format(args.TARGET))
+
+    if not args.corpora:
+        args.corpora = abs_join(CORPORA_DIR, args.TARGET)
+    if not args.artifact:
+        args.artifact = abs_join(CORPORA_DIR, '{}-crash'.format(args.TARGET))
+    if not args.seed:
+        args.seed = abs_join(CORPORA_DIR, '{}-seed'.format(args.TARGET))
+
+    return args
+
+
+def libfuzzer(args):
+    try:
+        args = libfuzzer_parser(args)
+    except Exception as e:
+        print(e)
+        return 1
+    target = abs_join(FUZZ_DIR, args.TARGET)
+
+    corpora = [create(args.corpora)]
+    artifact = create(args.artifact)
+    seed = check(args.seed)
+
+    corpora += [artifact]
+    if seed is not None:
+        corpora += [seed]
+
+    cmd = [target, '-artifact_prefix={}/'.format(artifact)]
+    cmd += corpora + args.extra
+    print(' '.join(cmd))
+    subprocess.call(cmd)
+    return 0
+
+
+def afl_parser(args):
+    description = """
+    Runs an afl-fuzz job.
+    Passes all extra arguments to afl-fuzz.
+    The fuzzer should have been built with CC/CXX set to the AFL compilers,
+    and with LIB_FUZZING_ENGINE='libregression.a'.
+    Takes input from CORPORA and writes output to OUTPUT.
+    Uses AFL_FUZZ as the binary (set from flag or environment variable).
+    """
+    parser = argparse.ArgumentParser(prog=args.pop(0), description=description)
+    parser.add_argument(
+        '--corpora',
+        type=str,
+        help='Override the default corpora dir (default: {})'.format(
+            abs_join(CORPORA_DIR, 'TARGET')))
+    parser.add_argument(
+        '--output',
+        type=str,
+        help='Override the default AFL output dir (default: {})'.format(
+            abs_join(CORPORA_DIR, 'TARGET-afl')))
+    parser.add_argument(
+        '--afl-fuzz',
+        type=str,
+        default=AFL_FUZZ,
+        help='AFL_FUZZ (default: $AFL_FUZZ={})'.format(AFL_FUZZ))
+    parser.add_argument(
+        'TARGET',
+        type=str,
+        help='Fuzz target(s) to build {{{}}}'.format(', '.join(TARGETS)))
+    args, extra = parser.parse_known_args(args)
+    args.extra = extra
+
+    if args.TARGET and args.TARGET not in TARGETS:
+        raise RuntimeError('{} is not a valid target'.format(args.TARGET))
+
+    if not args.corpora:
+        args.corpora = abs_join(CORPORA_DIR, args.TARGET)
+    if not args.output:
+        args.output = abs_join(CORPORA_DIR, '{}-afl'.format(args.TARGET))
+
+    return args
+
+
+def afl(args):
+    try:
+        args = afl_parser(args)
+    except Exception as e:
+        print(e)
+        return 1
+    target = abs_join(FUZZ_DIR, args.TARGET)
+
+    corpora = create(args.corpora)
+    output = create(args.output)
+
+    cmd = [args.afl_fuzz, '-i', corpora, '-o', output] + args.extra
+    cmd += [target, '@@']
+    print(' '.join(cmd))
+    subprocess.call(cmd)
+    return 0
+
+
+def regression_parser(args):
+    description = """
+    Runs one or more regression tests.
+    The fuzzer should have been built with with
+    LIB_FUZZING_ENGINE='libregression.a'.
+    Takes input from CORPORA.
+    """
+    parser = argparse.ArgumentParser(prog=args.pop(0), description=description)
+    parser.add_argument(
+        'TARGET',
+        nargs='*',
+        type=str,
+        help='Fuzz target(s) to build {{{}}}'.format(', '.join(ALL_TARGETS)))
+    args = parser.parse_args(args)
+
+    targets = set()
+    for target in args.TARGET:
+        if not target:
+            continue
+        if target == 'all':
+            targets = targets.union(TARGETS)
+        elif target in TARGETS:
+            targets.add(target)
+        else:
+            raise RuntimeError('{} is not a valid target'.format(target))
+    args.TARGET = list(targets)
+
+    return args
+
+
+def regression(args):
+    try:
+        args = regression_parser(args)
+    except Exception as e:
+        print(e)
+        return 1
+    for target in args.TARGET:
+        corpora = create(abs_join(CORPORA_DIR, target))
+        target = abs_join(FUZZ_DIR, target)
+        cmd = [target, corpora]
+        print(' '.join(cmd))
+        subprocess.check_call(cmd)
+    return 0
+
+
+def gen_parser(args):
+    description = """
+    Generate a seed corpus appropiate for TARGET with data generated with
+    decodecorpus.
+    The fuzz inputs are prepended with a seed before the zstd data, so the
+    output of decodecorpus shouldn't be used directly.
+    Generates NUMBER samples prepended with FUZZ_RNG_SEED_SIZE random bytes and
+    puts the output in SEED.
+    DECODECORPUS is the decodecorpus binary, and must already be built.
+    """
+    parser = argparse.ArgumentParser(prog=args.pop(0), description=description)
+    parser.add_argument(
+        '--number',
+        '-n',
+        type=int,
+        default=100,
+        help='Number of samples to generate')
+    parser.add_argument(
+        '--max-size-log',
+        type=int,
+        default=13,
+        help='Maximum sample size to generate')
+    parser.add_argument(
+        '--seed',
+        type=str,
+        help='Override the default seed dir (default: {})'.format(
+            abs_join(CORPORA_DIR, 'TARGET-seed')))
+    parser.add_argument(
+        '--decodecorpus',
+        type=str,
+        default=DECODECORPUS,
+        help="decodecorpus binary (default: $DECODECORPUS='{}')".format(
+            DECODECORPUS))
+    parser.add_argument(
+        '--fuzz-rng-seed-size',
+        type=int,
+        default=4,
+        help="FUZZ_RNG_SEED_SIZE used for generate the samples (must match)"
+    )
+    parser.add_argument(
+        'TARGET',
+        type=str,
+        help='Fuzz target(s) to build {{{}}}'.format(', '.join(TARGETS)))
+    args, extra = parser.parse_known_args(args)
+    args.extra = extra
+
+    if args.TARGET and args.TARGET not in TARGETS:
+        raise RuntimeError('{} is not a valid target'.format(args.TARGET))
+
+    if not args.seed:
+        args.seed = abs_join(CORPORA_DIR, '{}-seed'.format(args.TARGET))
+
+    if not os.path.isfile(args.decodecorpus):
+        raise RuntimeError("{} is not a file run 'make -C {} decodecorpus'".
+                           format(args.decodecorpus, abs_join(FUZZ_DIR, '..')))
+
+    return args
+
+
+def gen(args):
+    try:
+        args = gen_parser(args)
+    except Exception as e:
+        print(e)
+        return 1
+
+    seed = create(args.seed)
+    with tmpdir() as compressed:
+        with tmpdir() as decompressed:
+            cmd = [
+                args.decodecorpus,
+                '-n{}'.format(args.number),
+                '-p{}/'.format(compressed),
+                '-o{}'.format(decompressed),
+            ]
+
+            if 'block_' in args.TARGET:
+                cmd += [
+                    '--gen-blocks',
+                    '--max-block-size-log={}'.format(args.max_size_log)
+                ]
+            else:
+                cmd += ['--max-content-size-log={}'.format(args.max_size_log)]
+
+            print(' '.join(cmd))
+            subprocess.check_call(cmd)
+
+            if '_round_trip' in args.TARGET:
+                print('using decompressed data in {}'.format(decompressed))
+                samples = decompressed
+            elif '_decompress' in args.TARGET:
+                print('using compressed data in {}'.format(compressed))
+                samples = compressed
+
+            # Copy the samples over and prepend the RNG seeds
+            for name in os.listdir(samples):
+                samplename = abs_join(samples, name)
+                outname = abs_join(seed, name)
+                rng_seed = os.urandom(args.fuzz_rng_seed_size)
+                with open(samplename, 'rb') as sample:
+                    with open(outname, 'wb') as out:
+                        out.write(rng_seed)
+                        CHUNK_SIZE = 131072
+                        chunk = sample.read(CHUNK_SIZE)
+                        while len(chunk) > 0:
+                            out.write(chunk)
+                            chunk = sample.read(CHUNK_SIZE)
+    return 0
+
+
+def short_help(args):
+    name = args[0]
+    print("Usage: {} [OPTIONS] COMMAND [ARGS]...\n".format(name))
+
+
+def help(args):
+    short_help(args)
+    print("\tfuzzing helpers (select a command and pass -h for help)\n")
+    print("Options:")
+    print("\t-h, --help\tPrint this message")
+    print("")
+    print("Commands:")
+    print("\tbuild\t\tBuild a fuzzer")
+    print("\tlibfuzzer\tRun a libFuzzer fuzzer")
+    print("\tafl\t\tRun an AFL fuzzer")
+    print("\tregression\tRun a regression test")
+    print("\tgen\t\tGenerate a seed corpus for a fuzzer")
+
+
+def main():
+    args = sys.argv
+    if len(args) < 2:
+        help(args)
+        return 1
+    if args[1] == '-h' or args[1] == '--help' or args[1] == '-H':
+        help(args)
+        return 1
+    command = args.pop(1)
+    args[0] = "{} {}".format(args[0], command)
+    if command == "build":
+        return build(args)
+    if command == "libfuzzer":
+        return libfuzzer(args)
+    if command == "regression":
+        return regression(args)
+    if command == "afl":
+        return afl(args)
+    if command == "gen":
+        return gen(args)
+    short_help(args)
+    print("Error: No such command {} (pass -h for help)".format(command))
+    return 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/tests/fuzz/fuzz_helpers.h b/tests/fuzz/fuzz_helpers.h
index f7cc3d5b..cb3421bb 100644
--- a/tests/fuzz/fuzz_helpers.h
+++ b/tests/fuzz/fuzz_helpers.h
@@ -19,6 +19,10 @@
 #include <stdint.h>
 #include <stdio.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define MIN(a, b) ((a) < (b) ? (a) : (b))
 #define MAX(a, b) ((a) > (b) ? (a) : (b))
 
@@ -48,11 +52,14 @@
 
 /**
  * Determininistically constructs a seed based on the fuzz input.
- * Only looks at the first FUZZ_RNG_SEED_SIZE bytes of the input.
+ * Consumes up to the first FUZZ_RNG_SEED_SIZE bytes of the input.
  */
-FUZZ_STATIC uint32_t FUZZ_seed(const uint8_t *src, size_t size) {
-  size_t const toHash = MIN(FUZZ_RNG_SEED_SIZE, size);
-  return XXH32(src, toHash, 0);
+FUZZ_STATIC uint32_t FUZZ_seed(uint8_t const **src, size_t* size) {
+  uint8_t const *data = *src;
+  size_t const toHash = MIN(FUZZ_RNG_SEED_SIZE, *size);
+  *size -= toHash;
+  *src += toHash;
+  return XXH32(data, toHash, 0);
 }
 
 #define FUZZ_rotl32(x, r) (((x) << (r)) | ((x) >> (32 - (r))))
@@ -67,4 +74,8 @@ FUZZ_STATIC uint32_t FUZZ_rand(uint32_t *state) {
   return rand32 >> 5;
 }
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif
diff --git a/tests/fuzz/regression_driver.c b/tests/fuzz/regression_driver.c
index 36ae3884..2b714d29 100644
--- a/tests/fuzz/regression_driver.c
+++ b/tests/fuzz/regression_driver.c
@@ -29,9 +29,11 @@ int main(int argc, char const **argv) {
 #ifdef UTIL_HAS_CREATEFILELIST
   files = UTIL_createFileList(files, numFiles, &fileNamesBuf, &numFiles,
                               kFollowLinks);
-  FUZZ_ASSERT(files);
+  if (!files)
+    numFiles = 0;
 #endif
-
+  if (numFiles == 0)
+    fprintf(stderr, "WARNING: No files passed to %s\n", argv[0]);
   for (i = 0; i < numFiles; ++i) {
     char const *fileName = files[i];
     size_t const fileSize = UTIL_getFileSize(fileName);
diff --git a/tests/fuzz/simple_decompress.c b/tests/fuzz/simple_decompress.c
index a225b9dc..bba272c6 100644
--- a/tests/fuzz/simple_decompress.c
+++ b/tests/fuzz/simple_decompress.c
@@ -24,7 +24,10 @@ static size_t bufSize = 0;
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
-    size_t const neededBufSize = MAX(20 * size, (size_t)256 << 10);
+    size_t neededBufSize;
+
+    FUZZ_seed(&src, &size);
+    neededBufSize = MAX(20 * size, (size_t)256 << 10);
 
     /* Allocate all buffers and contexts if not already allocated */
     if (neededBufSize > bufSize) {
@@ -39,7 +42,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
     }
     ZSTD_decompressDCtx(dctx, rBuf, neededBufSize, src, size);
 
-#ifndef STATEFULL_FUZZING
+#ifndef STATEFUL_FUZZING
     ZSTD_freeDCtx(dctx); dctx = NULL;
 #endif
     return 0;
diff --git a/tests/fuzz/simple_round_trip.c b/tests/fuzz/simple_round_trip.c
index 63472bb4..9df02528 100644
--- a/tests/fuzz/simple_round_trip.c
+++ b/tests/fuzz/simple_round_trip.c
@@ -44,9 +44,10 @@ static size_t roundTripTest(void *result, size_t resultCapacity,
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
-    size_t const neededBufSize = ZSTD_compressBound(size);
+    size_t neededBufSize;
 
-    seed = FUZZ_seed(src, size);
+    seed = FUZZ_seed(&src, &size);
+    neededBufSize = ZSTD_compressBound(size);
 
     /* Allocate all buffers and contexts if not already allocated */
     if (neededBufSize > bufSize) {
@@ -73,7 +74,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
         FUZZ_ASSERT_MSG(result == size, "Incorrect regenerated size");
         FUZZ_ASSERT_MSG(!memcmp(src, rBuf, size), "Corruption!");
     }
-#ifndef STATEFULL_FUZZING
+#ifndef STATEFUL_FUZZING
     ZSTD_freeCCtx(cctx); cctx = NULL;
     ZSTD_freeDCtx(dctx); dctx = NULL;
 #endif
diff --git a/tests/fuzz/stream_decompress.c b/tests/fuzz/stream_decompress.c
index dfd74697..7ad57122 100644
--- a/tests/fuzz/stream_decompress.c
+++ b/tests/fuzz/stream_decompress.c
@@ -51,7 +51,7 @@ static ZSTD_inBuffer makeInBuffer(const uint8_t **src, size_t *size)
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
-    seed = FUZZ_seed(src, size);
+    seed = FUZZ_seed(&src, &size);
 
     /* Allocate all buffers and contexts if not already allocated */
     if (!buf) {
@@ -78,7 +78,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
     }
 
 error:
-#ifndef STATEFULL_FUZZING
+#ifndef STATEFUL_FUZZING
     ZSTD_freeDStream(dstream); dstream = NULL;
 #endif
     return 0;
diff --git a/tests/fuzz/stream_round_trip.c b/tests/fuzz/stream_round_trip.c
index 74adbeab..e796c1e7 100644
--- a/tests/fuzz/stream_round_trip.c
+++ b/tests/fuzz/stream_round_trip.c
@@ -114,9 +114,10 @@ static size_t compress(uint8_t *dst, size_t capacity,
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
-    size_t const neededBufSize = ZSTD_compressBound(size) * 2;
+    size_t neededBufSize;
 
-    seed = FUZZ_seed(src, size);
+    seed = FUZZ_seed(&src, &size);
+    neededBufSize = ZSTD_compressBound(size) * 2;
 
     /* Allocate all buffers and contexts if not already allocated */
     if (neededBufSize > bufSize) {
@@ -145,7 +146,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
         FUZZ_ASSERT_MSG(!memcmp(src, rBuf, size), "Corruption!");
     }
 
-#ifndef STATEFULL_FUZZING
+#ifndef STATEFUL_FUZZING
     ZSTD_freeCStream(cstream); cstream = NULL;
     ZSTD_freeDCtx(dctx); dctx = NULL;
 #endif