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diff --git a/src/fmt/test/fuzzing/fuzzer_common.h b/src/fmt/test/fuzzing/fuzzer_common.h
new file mode 100644
index 000000000..c3d85619a
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+++ b/src/fmt/test/fuzzing/fuzzer_common.h
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+#ifndef FUZZER_COMMON_H
+#define FUZZER_COMMON_H
+
+// Copyright (c) 2019, Paul Dreik
+// License: see LICENSE.rst in the fmt root directory
+
+#include <cstdint>      // std::uint8_t
+#include <cstring>      // memcpy
+#include <type_traits>  // trivially copyable
+
+// one can format to either a string, or a buf. buf is faster,
+// but one may be interested in formatting to a string instead to
+// verify it works as intended. to avoid a combinatoric explosion,
+// select this at compile time instead of dynamically from the fuzz data
+#define FMT_FUZZ_FORMAT_TO_STRING 0
+
+// if fmt is given a buffer that is separately allocated,
+// chances that address sanitizer detects out of bound reads is
+// much higher. However, it slows down the fuzzing.
+#define FMT_FUZZ_SEPARATE_ALLOCATION 1
+
+// To let the the fuzzer mutation be efficient at cross pollinating
+// between different types, use a fixed size format.
+// The same bit pattern, interpreted as another type,
+// is likely interesting.
+// For this, we must know the size of the largest possible type in use.
+
+// There are some problems on travis, claiming Nfixed is not a constant
+// expression which seems to be an issue with older versions of libstdc++
+#if _GLIBCXX_RELEASE >= 7
+#  include <algorithm>
+namespace fmt_fuzzer {
+constexpr auto Nfixed = std::max(sizeof(long double), sizeof(std::intmax_t));
+}
+#else
+namespace fmt_fuzzer {
+constexpr auto Nfixed = 16;
+}
+#endif
+
+namespace fmt_fuzzer {
+// view data as a c char pointer.
+template <typename T> inline const char* as_chars(const T* data) {
+  return static_cast<const char*>(static_cast<const void*>(data));
+}
+
+// view data as a byte pointer
+template <typename T> inline const std::uint8_t* as_bytes(const T* data) {
+  return static_cast<const std::uint8_t*>(static_cast<const void*>(data));
+}
+
+// blits bytes from Data to form an (assumed trivially constructible) object
+// of type Item
+template <class Item> inline Item assignFromBuf(const std::uint8_t* Data) {
+  Item item{};
+  std::memcpy(&item, Data, sizeof(Item));
+  return item;
+}
+
+// reads a boolean value by looking at the first byte from Data
+template <> inline bool assignFromBuf<bool>(const std::uint8_t* Data) {
+  return !!Data[0];
+}
+
+}  // namespace fmt_fuzzer
+
+#endif  // FUZZER_COMMON_H