[libc] Improve testing of mem functions

[gchatelet]

Summary

This patch extracts the testing logic from op_tests.cpp into
memory_check_utils.h so we can reuse it for mem* function integration
tests.

This makes testing consistent and thorough.
For instance this catches a bug that got unnoticed during submission of
D136595 and D135134. Integration test for memcmp was only testing a
single size.

This also leverages ASAN to make sure that data is not read / written
outside permitted boundaries

[gchatelet]

Fix documentation and make code less convoluted

[courbet]

libc/test/src/string/bcmp_test.cpp

45

SizeSweep or AllSizes would be clearer IMO (here and below).

46

kMaxSize (here and below)

[courbet]

libc/test/src/string/memory_utils/memory_check_utils.h

33

poisons

88

Maybe call this ReferenceCopy top make it clear that this is assumed to be correct.

88

Can we mark this with attribute nobuiltin to make it clear that this is the implementation we get ? Or maybe even add an #ifndef NOBUILTIN #error "should be built with -fno-builtin" (I'm not sure whether clang exports such a define, but if it does...).

It would be a shame if we were to compare memcpy against memcpy :)

[gchatelet]

• fixup! [libc] Improve testing of mem functions

[gchatelet]

I'm submitting this patch. Let me know if you have any other comments.

libc/test/src/string/bcmp_test.cpp

 //===-- Unittests for bcmp ------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
+#include "memory_utils/memory_check_utils.h"
 #include "src/string/bcmp.h"
 #include "utils/UnitTest/Test.h"
 
+namespace __llvm_libc {
+
 TEST(LlvmLibcBcmpTest, CmpZeroByte) {
   const char *lhs = "ab";
   const char *rhs = "bc";
   ASSERT_EQ(__llvm_libc::bcmp(lhs, rhs, 0), 0);
 }
 
 TEST(LlvmLibcBcmpTest, LhsRhsAreTheSame) {
   const char *lhs = "ab";
   const char *rhs = "ab";
   ASSERT_EQ(__llvm_libc::bcmp(lhs, rhs, 2), 0);
 }
 
 TEST(LlvmLibcBcmpTest, LhsBeforeRhsLexically) {
   const char *lhs = "ab";
   const char *rhs = "ac";
   ASSERT_NE(__llvm_libc::bcmp(lhs, rhs, 2), 0);
 }
 
 TEST(LlvmLibcBcmpTest, LhsAfterRhsLexically) {
   const char *lhs = "ac";
   const char *rhs = "ab";
   ASSERT_NE(__llvm_libc::bcmp(lhs, rhs, 2), 0);
 }
 
-TEST(LlvmLibcBcmpTest, Sweep) {
-  static constexpr size_t K_MAX_SIZE = 1024;
-  char lhs[K_MAX_SIZE];
-  char rhs[K_MAX_SIZE];
-
-  const auto reset = [](char *const ptr) {
-    for (size_t i = 0; i < K_MAX_SIZE; ++i)
-      ptr[i] = 'a';
-  };
-
-  reset(lhs);
-  reset(rhs);
-  for (size_t i = 0; i < K_MAX_SIZE; ++i)
-    ASSERT_EQ(__llvm_libc::bcmp(lhs, rhs, i), 0);
-
-  reset(lhs);
-  reset(rhs);
-  for (size_t i = 0; i < K_MAX_SIZE; ++i) {
-    rhs[i] = 'b';
-    ASSERT_NE(__llvm_libc::bcmp(lhs, rhs, K_MAX_SIZE), 0);
-    rhs[i] = 'a';
+// Adapt CheckBcmp signature to op implementation signatures.
+template <auto FnImpl>
+int CmpAdaptor(cpp::span<char> p1, cpp::span<char> p2, size_t size) {
+  return FnImpl(p1.begin(), p2.begin(), size);
+}
+
+TEST(LlvmLibcBcmpTest, Thorough) {
+  static constexpr size_t kSize = 1024;
+  static constexpr auto Impl = CmpAdaptor<__llvm_libc::bcmp>;
+  Buffer Buffer1(kSize);
+  Buffer Buffer2(kSize);
+  Randomize(Buffer1.span());
+  for (size_t size = 0; size < kSize; ++size) {
+    auto span1 = Buffer1.span().subspan(0, size);
+    auto span2 = Buffer2.span().subspan(0, size);
+    ASSERT_TRUE((CheckBcmp<Impl>(span1, span2, size)));
   }
 }
+
+} // namespace __llvm_libc

libc/test/src/string/bzero_test.cpp

 //===-- Unittests for bzero -----------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-#include "src/__support/CPP/span.h"
+#include "memory_utils/memory_check_utils.h"
 #include "src/string/bzero.h"
 #include "utils/UnitTest/Test.h"
 
-using __llvm_libc::cpp::array;
-using __llvm_libc::cpp::span;
-using Data = array<char, 2048>;
+namespace __llvm_libc {
 
-static const span<const char> k_deadcode("DEADC0DE", 8);
-
-// Returns a Data object filled with a repetition of `filler`.
-Data get_data(span<const char> filler) {
-  Data out;
-  for (size_t i = 0; i < out.size(); ++i)
-    out[i] = filler[i % filler.size()];
-  return out;
+// Adapt CheckMemset signature to op implementation signatures.
+template <auto FnImpl>
+void BzeroAdaptor(cpp::span<char> p1, uint8_t value, size_t size) {
+  assert(value == 0);
+  FnImpl(p1.begin(), size);
 }
 
 TEST(LlvmLibcBzeroTest, Thorough) {
-  const Data dirty = get_data(k_deadcode);
-  for (size_t count = 0; count < 1024; ++count) {
-    for (size_t align = 0; align < 64; ++align) {
-      auto buffer = dirty;
-      char *const dst = &buffer[align];
-      __llvm_libc::bzero(dst, count);
-      // Everything before copy is untouched.
-      for (size_t i = 0; i < align; ++i)
-        ASSERT_EQ(buffer[i], dirty[i]);
-      // Everything in between is copied.
-      for (size_t i = 0; i < count; ++i)
-        ASSERT_EQ(buffer[align + i], char(0));
-      // Everything after copy is untouched.
-      for (size_t i = align + count; i < dirty.size(); ++i)
-        ASSERT_EQ(buffer[i], dirty[i]);
-    }
+  static constexpr size_t kSize = 1024;
+  static constexpr auto Impl = BzeroAdaptor<__llvm_libc::bzero>;
+  Buffer DstBuffer(kSize);
+  for (size_t size = 0; size < kSize; ++size) {
+    auto dst = DstBuffer.span().subspan(0, size);
+    ASSERT_TRUE((CheckMemset<Impl>(dst, 0, size)));
   }
 }
 
-// FIXME: Add tests with reads and writes on the boundary of a read/write
-// protected page to check we're not reading nor writing prior/past the allowed
-// regions.
+} // namespace __llvm_libc

libc/test/src/string/memcmp_test.cpp

 //===-- Unittests for memcmp ----------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
+#include "memory_utils/memory_check_utils.h"
 #include "src/string/memcmp.h"
 #include "utils/UnitTest/Test.h"
 
+namespace __llvm_libc {
+
 TEST(LlvmLibcMemcmpTest, CmpZeroByte) {
   const char *lhs = "ab";
   const char *rhs = "yz";
   EXPECT_EQ(__llvm_libc::memcmp(lhs, rhs, 0), 0);
 }
 
 TEST(LlvmLibcMemcmpTest, LhsRhsAreTheSame) {
   const char *lhs = "ab";
   const char *rhs = "ab";
   EXPECT_EQ(__llvm_libc::memcmp(lhs, rhs, 2), 0);
 }
 
 TEST(LlvmLibcMemcmpTest, LhsBeforeRhsLexically) {
   const char *lhs = "ab";
   const char *rhs = "az";
   EXPECT_LT(__llvm_libc::memcmp(lhs, rhs, 2), 0);
 }
 
 TEST(LlvmLibcMemcmpTest, LhsAfterRhsLexically) {
   const char *lhs = "az";
   const char *rhs = "ab";
   EXPECT_GT(__llvm_libc::memcmp(lhs, rhs, 2), 0);
 }
 
-TEST(LlvmLibcMemcmpTest, Sweep) {
-  static constexpr size_t K_MAX_SIZE = 1024;
-  char lhs[K_MAX_SIZE];
-  char rhs[K_MAX_SIZE];
-
-  const auto reset = [](char *const ptr) {
-    for (size_t i = 0; i < K_MAX_SIZE; ++i)
-      ptr[i] = 'a';
-  };
-
-  reset(lhs);
-  reset(rhs);
-  for (size_t i = 0; i < K_MAX_SIZE; ++i)
-    ASSERT_EQ(__llvm_libc::memcmp(lhs, rhs, i), 0);
-
-  reset(lhs);
-  reset(rhs);
-  for (size_t i = 0; i < K_MAX_SIZE; ++i) {
-    rhs[i] = 'z';
-    ASSERT_LT(__llvm_libc::memcmp(lhs, rhs, K_MAX_SIZE), 0);
-    rhs[i] = 'a';
+// Adapt CheckMemcmp signature to op implementation signatures.
+template <auto FnImpl>
+int CmpAdaptor(cpp::span<char> p1, cpp::span<char> p2, size_t size) {
+  return FnImpl(p1.begin(), p2.begin(), size);
+}
+
+TEST(LlvmLibcMemcmpTest, Thorough) {
+  static constexpr size_t kSize = 1024;
+  static constexpr auto Impl = CmpAdaptor<__llvm_libc::memcmp>;
+  Buffer Buffer1(kSize);
+  Buffer Buffer2(kSize);
+  Randomize(Buffer1.span());
+  for (size_t size = 0; size < kSize; ++size) {
+    auto span1 = Buffer1.span().subspan(0, size);
+    auto span2 = Buffer2.span().subspan(0, size);
+    ASSERT_TRUE((CheckMemcmp<Impl>(span1, span2, size)));
   }
 }
+
+} // namespace __llvm_libc

libc/test/src/string/memcpy_test.cpp

 //===-- Unittests for memcpy ----------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-#include "src/__support/CPP/span.h"
+#include "memory_utils/memory_check_utils.h"
 #include "src/string/memcpy.h"
 #include "utils/UnitTest/Test.h"
 
-using __llvm_libc::cpp::array;
-using __llvm_libc::cpp::span;
-using Data = array<char, 2048>;
+namespace __llvm_libc {
 
-static const span<const char> k_numbers("0123456789", 10);
-static const span<const char> k_deadcode("DEADC0DE", 8);
-
-// Returns a Data object filled with a repetition of `filler`.
-Data get_data(span<const char> filler) {
-  Data out;
-  for (size_t i = 0; i < out.size(); ++i)
-    out[i] = filler[i % filler.size()];
-  return out;
+// Adapt CheckMemcpy signature to op implementation signatures.
+template <auto FnImpl>
+void CopyAdaptor(cpp::span<char> dst, cpp::span<char> src, size_t size) {
+  FnImpl(dst.begin(), src.begin(), size);
 }
 
 TEST(LlvmLibcMemcpyTest, Thorough) {
-  const Data groundtruth = get_data(k_numbers);
-  const Data dirty = get_data(k_deadcode);
-  for (size_t count = 0; count < 1024; ++count) {
-    for (size_t align = 0; align < 64; ++align) {
-      auto buffer = dirty;
-      const char *const src = groundtruth.data();
-      void *const dst = &buffer[align];
-      void *const ret = __llvm_libc::memcpy(dst, src, count);
-      // Return value is `dst`.
-      ASSERT_EQ(ret, dst);
-      // Everything before copy is untouched.
-      for (size_t i = 0; i < align; ++i)
-        ASSERT_EQ(buffer[i], dirty[i]);
-      // Everything in between is copied.
-      for (size_t i = 0; i < count; ++i)
-        ASSERT_EQ(buffer[align + i], groundtruth[i]);
-      // Everything after copy is untouched.
-      for (size_t i = align + count; i < dirty.size(); ++i)
-        ASSERT_EQ(buffer[i], dirty[i]);
-    }
+  static constexpr size_t kSize = 1024;
+  static constexpr auto Impl = CopyAdaptor<__llvm_libc::memcpy>;
+  Buffer SrcBuffer(kSize);
+  Buffer DstBuffer(kSize);
+  Randomize(SrcBuffer.span());
+  for (size_t size = 0; size < kSize; ++size) {
+    auto src = SrcBuffer.span().subspan(0, size);
+    auto dst = DstBuffer.span().subspan(0, size);
+    ASSERT_TRUE(CheckMemcpy<Impl>(dst, src, size));
   }
 }
 
-// FIXME: Add tests with reads and writes on the boundary of a read/write
-// protected page to check we're not reading nor writing prior/past the allowed
-// regions.
+} // namespace __llvm_libc

libc/test/src/string/memory_utils/memory_check_utils.h

+//===-- Utils to test conformance of mem functions ------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LIBC_TEST_SRC_STRING_MEMORY_UTILS_MEMORY_CHECK_UTILS_H
+#define LIBC_TEST_SRC_STRING_MEMORY_UTILS_MEMORY_CHECK_UTILS_H
+
+#include "src/__support/CPP/span.h"
+#include "src/string/memory_utils/utils.h"
+#include <assert.h> // assert
+#include <stddef.h> // size_t
+#include <stdint.h> // uintxx_t
+#include <stdlib.h> // malloc/free
+
+#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
+#include <sanitizer/asan_interface.h>
+#define ASAN_POISON_MEMORY_REGION(addr, size)                                  \
+  __asan_poison_memory_region((addr), (size))
+#define ASAN_UNPOISON_MEMORY_REGION(addr, size)                                \
+  __asan_unpoison_memory_region((addr), (size))
+#else
+#define ASAN_POISON_MEMORY_REGION(addr, size) ((void)(addr), (void)(size))
+#define ASAN_UNPOISON_MEMORY_REGION(addr, size) ((void)(addr), (void)(size))
+#endif
+
+namespace __llvm_libc {
+
+// Simple structure to allocate a buffer of a particular size.
+// When ASAN is present it also poison the whole memory.
+// This is a utility class to be used by Buffer below, do not use directly.
+struct PoisonedBuffer {
+  PoisonedBuffer(size_t size) : ptr((char *)malloc(size)) {
+    assert(ptr);
+    ASAN_POISON_MEMORY_REGION(ptr, size);
+  }
+  ~PoisonedBuffer() { free(ptr); }
+
+protected:
+  char *ptr = nullptr;
+};
+
+// Simple structure to allocate a buffer (aligned or not) of a particular size.
+// It is backed by a wider buffer that is marked poisoned when ASAN is present.
+// The requested region is unpoisoned, this allows catching out of bounds
+// accesses.
+enum class Aligned : bool { NO = false, YES = true };
+struct Buffer : private PoisonedBuffer {
+  static constexpr size_t kAlign = 64;
+  static constexpr size_t kLeeway = 2 * kAlign;
+  Buffer(size_t size, Aligned aligned = Aligned::YES)
+      : PoisonedBuffer(size + kLeeway), size(size) {
+    offset_ptr = ptr;
+    offset_ptr += distance_to_next_aligned<kAlign>(ptr);
+    assert((uintptr_t)(offset_ptr) % kAlign == 0);
+    if (aligned == Aligned::NO)
+      ++offset_ptr;
+    assert(offset_ptr > ptr);
+    assert((offset_ptr + size) < (ptr + size + kLeeway));
+    ASAN_UNPOISON_MEMORY_REGION(offset_ptr, size);
+  }
+  cpp::span<char> span() { return cpp::span<char>(offset_ptr, size); }
+
+private:
+  size_t size = 0;
+  char *offset_ptr = nullptr;
+};
+
+static inline char GetRandomChar() {
+  static constexpr const uint64_t a = 1103515245;
+  static constexpr const uint64_t c = 12345;
+  static constexpr const uint64_t m = 1ULL << 31;
+  static uint64_t seed = 123456789;
+  seed = (a * seed + c) % m;
+  return seed;
+}
+
+// Randomize the content of the buffer.
+static inline void Randomize(cpp::span<char> buffer) {
+  for (auto &current : buffer)
+    current = GetRandomChar();
+}
+
+// Copy one span to another.
+static inline void Copy(cpp::span<char> dst, const cpp::span<char> src) {
+  assert(dst.size() == src.size());
+  for (size_t i = 0; i < dst.size(); ++i)
+    dst[i] = src[i];
+}
+
+// Checks that FnImpl implements the memcpy semantic.
+template <auto FnImpl>
+bool CheckMemcpy(cpp::span<char> dst, cpp::span<char> src, size_t size) {
+  assert(dst.size() == src.size());
+  assert(dst.size() == size);
+  Randomize(dst);
+  FnImpl(dst, src, size);
+  for (size_t i = 0; i < size; ++i)
+    if (dst[i] != src[i])
+      return false;
+  return true;
+}
+
+// Checks that FnImpl implements the memset semantic.
+template <auto FnImpl>
+bool CheckMemset(cpp::span<char> dst, uint8_t value, size_t size) {
+  Randomize(dst);
+  FnImpl(dst, value, size);
+  for (char c : dst)
+    if (c != (char)value)
+      return false;
+  return true;
+}
+
+// Checks that FnImpl implements the bcmp semantic.
+template <auto FnImpl>
+bool CheckBcmp(cpp::span<char> span1, cpp::span<char> span2, size_t size) {
+  assert(span1.size() == span2.size());
+  Copy(span2, span1);
+  // Compare equal
+  if (int cmp = FnImpl(span1, span2, size); cmp != 0)
+    return false;
+  // Compare not equal if any byte differs
+  for (size_t i = 0; i < size; ++i) {
+    ++span2[i];
+    if (int cmp = FnImpl(span1, span2, size); cmp == 0)
+      return false;
+    if (int cmp = FnImpl(span2, span1, size); cmp == 0)
+      return false;
+    --span2[i];
+  }
+  return true;
+}
+
+// Checks that FnImpl implements the memcmp semantic.
+template <auto FnImpl>
+bool CheckMemcmp(cpp::span<char> span1, cpp::span<char> span2, size_t size) {
+  assert(span1.size() == span2.size());
+  Copy(span2, span1);
+  // Compare equal
+  if (int cmp = FnImpl(span1, span2, size); cmp != 0)
+    return false;
+  // Compare not equal if any byte differs
+  for (size_t i = 0; i < size; ++i) {
+    ++span2[i];
+    int ground_truth = __builtin_memcmp(span1.data(), span2.data(), size);
+    if (ground_truth > 0) {
+      if (int cmp = FnImpl(span1, span2, size); cmp <= 0)
+        return false;
+      if (int cmp = FnImpl(span2, span1, size); cmp >= 0)
+        return false;
+    } else {
+      if (int cmp = FnImpl(span1, span2, size); cmp >= 0)
+        return false;
+      if (int cmp = FnImpl(span2, span1, size); cmp <= 0)
+        return false;
+    }
+    --span2[i];
+  }
+  return true;
+}
+
+// TODO: Also implement the memmove semantic
+
+} // namespace __llvm_libc
+
+#endif // LIBC_TEST_SRC_STRING_MEMORY_UTILS_MEMORY_CHECK_UTILS_H

libc/test/src/string/memory_utils/op_tests.cpp

 //===-- Unittests for op_ files -------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-#include "src/__support/CPP/limits.h"
-#include "src/__support/CPP/span.h"
+#include "memory_check_utils.h"
 #include "src/string/memory_utils/op_aarch64.h"
 #include "src/string/memory_utils/op_builtin.h"
 #include "src/string/memory_utils/op_generic.h"
 #include "src/string/memory_utils/op_x86.h"
-#include "src/string/memory_utils/utils.h"
 #include "utils/UnitTest/Test.h"
 
 #include <assert.h>
-#include <stdlib.h>
-
-// User code should use macros instead of functions.
-#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
-#include <sanitizer/asan_interface.h>
-#define ASAN_POISON_MEMORY_REGION(addr, size)                                  \
-  __asan_poison_memory_region((addr), (size))
-#define ASAN_UNPOISON_MEMORY_REGION(addr, size)                                \
-  __asan_unpoison_memory_region((addr), (size))
-#else
-#define ASAN_POISON_MEMORY_REGION(addr, size) ((void)(addr), (void)(size))
-#define ASAN_UNPOISON_MEMORY_REGION(addr, size) ((void)(addr), (void)(size))
-#endif
 
 #if defined(LLVM_LIBC_ARCH_X86_64) || defined(LLVM_LIBC_ARCH_AARCH64)
 #define LLVM_LIBC_HAS_UINT64
 #endif
 
 namespace __llvm_libc {
 
-static char GetRandomChar() {
-  static constexpr const uint64_t a = 1103515245;
-  static constexpr const uint64_t c = 12345;
-  static constexpr const uint64_t m = 1ULL << 31;
-  static uint64_t seed = 123456789;
-  seed = (a * seed + c) % m;
-  return seed;
-}
-
-// Randomize the content of the buffer.
-static void Randomize(cpp::span<char> buffer) {
-  for (auto &current : buffer)
-    current = GetRandomChar();
-}
-
-// Copy one span to another.
-static void Copy(cpp::span<char> dst, const cpp::span<char> src) {
-  assert(dst.size() == src.size());
-  for (size_t i = 0; i < dst.size(); ++i)
-    dst[i] = src[i];
-}
-
-cpp::byte *as_byte(cpp::span<char> span) {
-  return reinterpret_cast<cpp::byte *>(span.data());
-}
-
-// Simple structure to allocate a buffer of a particular size.
-struct PoisonedBuffer {
-  PoisonedBuffer(size_t size) : ptr((char *)malloc(size)) {
-    assert(ptr);
-    ASAN_POISON_MEMORY_REGION(ptr, size);
-  }
-  ~PoisonedBuffer() { free(ptr); }
-
-protected:
-  char *ptr = nullptr;
-};
-
-// Simple structure to allocate a buffer (aligned or not) of a particular size.
-// It is backed by a wider buffer that is marked poisoned when ASAN is present.
-// The requested region is unpoisoned, this allows catching out of bounds
-// accesses.
-enum class Aligned : bool { NO = false, YES = true };
-struct Buffer : private PoisonedBuffer {
-  static constexpr size_t kAlign = 64;
-  static constexpr size_t kLeeway = 2 * kAlign;
-  Buffer(size_t size, Aligned aligned = Aligned::YES)
-      : PoisonedBuffer(size + kLeeway), size(size) {
-    offset_ptr = ptr;
-    offset_ptr += distance_to_next_aligned<kAlign>(ptr);
-    assert((uintptr_t)(offset_ptr) % kAlign == 0);
-    if (aligned == Aligned::NO)
-      ++offset_ptr;
-    assert(offset_ptr > ptr);
-    assert((offset_ptr + size) < (ptr + size + kLeeway));
-    ASAN_UNPOISON_MEMORY_REGION(offset_ptr, size);
-  }
-  cpp::span<char> span() { return cpp::span<char>(offset_ptr, size); }
-
-private:
-  size_t size = 0;
-  char *offset_ptr = nullptr;
-};
-
 // Allocates two Buffer and extracts two spans out of them, one
 // aligned and one misaligned. Tests are run on both spans.
 struct Buffers {
   Buffers(size_t size)
       : aligned_buffer(size, Aligned::YES),
         misaligned_buffer(size, Aligned::NO) {}
 
   // Returns two spans of 'size' bytes. The first is aligned on
#ifdef LLVM_LIBC_HAS_BUILTIN_MEMCPY_INLINE
     builtin::Memcpy<4>,  //
     builtin::Memcpy<8>,  //
     builtin::Memcpy<16>, //
     builtin::Memcpy<32>, //
     builtin::Memcpy<64>
 #endif // LLVM_LIBC_HAS_BUILTIN_MEMCPY_INLINE
     >;
 
+// Convenient helper to turn a span into cpp::byte *.
+static inline cpp::byte *as_byte(cpp::span<char> span) {
+  return reinterpret_cast<cpp::byte *>(span.data());
+}
+
+// Adapt CheckMemcpy signature to op implementation signatures.
 template <auto FnImpl>
-bool CheckMemcpy(cpp::span<char> dst, cpp::span<char> src, size_t size) {
-  assert(dst.size() == src.size());
-  assert(dst.size() == size);
-  Randomize(dst);
+void CopyAdaptor(cpp::span<char> dst, cpp::span<char> src, size_t size) {
   FnImpl(as_byte(dst), as_byte(src), size);
-  for (size_t i = 0; i < size; ++i)
-    if (dst[i] != src[i])
-      return false;
-  return true;
 }
-
-template <typename T>
-static void MemcpyAdaptor(Ptr dst, CPtr src, size_t size) {
-  assert(size == T::SIZE);
-  return T::block(dst, src);
+template <size_t Size, auto FnImpl>
+void CopyBlockAdaptor(cpp::span<char> dst, cpp::span<char> src, size_t size) {
+  assert(size == Size);
+  FnImpl(as_byte(dst), as_byte(src));
 }
 
 TYPED_TEST(LlvmLibcOpTest, Memcpy, MemcpyImplementations) {
   using Impl = ParamType;
   constexpr size_t kSize = Impl::SIZE;
   { // Test block operation
+    static constexpr auto BlockImpl = CopyBlockAdaptor<kSize, Impl::block>;
     Buffers SrcBuffer(kSize);
     Buffers DstBuffer(kSize);
     for (auto src : SrcBuffer.spans()) {
       Randomize(src);
       for (auto dst : DstBuffer.spans()) {
-        ASSERT_TRUE(CheckMemcpy<MemcpyAdaptor<Impl>>(dst, src, kSize));
+        ASSERT_TRUE(CheckMemcpy<BlockImpl>(dst, src, kSize));
       }
     }
   }
   { // Test head tail operations from kSize to 2 * kSize.
+    static constexpr auto HeadTailImpl = CopyAdaptor<Impl::head_tail>;
     Buffer SrcBuffer(2 * kSize);
     Buffer DstBuffer(2 * kSize);
     Randomize(SrcBuffer.span());
     for (size_t size = kSize; size < 2 * kSize; ++size) {
       auto src = SrcBuffer.span().subspan(0, size);
       auto dst = DstBuffer.span().subspan(0, size);
-      ASSERT_TRUE(CheckMemcpy<Impl::head_tail>(dst, src, size));
+      ASSERT_TRUE(CheckMemcpy<HeadTailImpl>(dst, src, size));
     }
   }
   { // Test loop operations from kSize to 3 * kSize.
     if constexpr (kSize > 1) {
+      static constexpr auto LoopImpl = CopyAdaptor<Impl::loop_and_tail>;
       Buffer SrcBuffer(3 * kSize);
       Buffer DstBuffer(3 * kSize);
       Randomize(SrcBuffer.span());
       for (size_t size = kSize; size < 3 * kSize; ++size) {
         auto src = SrcBuffer.span().subspan(0, size);
         auto dst = DstBuffer.span().subspan(0, size);
-        ASSERT_TRUE(CheckMemcpy<Impl::loop_and_tail>(dst, src, size));
+        ASSERT_TRUE(CheckMemcpy<LoopImpl>(dst, src, size));
       }
     }
   }
 }
 
 using MemsetImplementations = testing::TypeList<
 #ifdef LLVM_LIBC_HAS_BUILTIN_MEMSET_INLINE
     builtin::Memset<1>,  //
#endif
     generic::Memset<4, 4>,   //
     generic::Memset<16, 16>, //
     generic::Memset<32, 16>, //
     generic::Memset<64, 16>, //
     generic::Memset<32, 32>, //
     generic::Memset<64, 32>  //
     >;
 
+// Adapt CheckMemset signature to op implementation signatures.
 template <auto FnImpl>
-bool CheckMemset(cpp::span<char> dst, uint8_t value, size_t size) {
-  Randomize(dst);
+void SetAdaptor(cpp::span<char> dst, uint8_t value, size_t size) {
   FnImpl(as_byte(dst), value, size);
-  for (char c : dst)
-    if (c != (char)value)
-      return false;
-  return true;
 }
-
-template <typename T>
-static void MemsetAdaptor(Ptr dst, uint8_t value, size_t size) {
-  assert(size == T::SIZE);
-  return T::block(dst, value);
+template <size_t Size, auto FnImpl>
+void SetBlockAdaptor(cpp::span<char> dst, uint8_t value, size_t size) {
+  assert(size == Size);
+  FnImpl(as_byte(dst), value);
 }
 
 TYPED_TEST(LlvmLibcOpTest, Memset, MemsetImplementations) {
   using Impl = ParamType;
   constexpr size_t kSize = Impl::SIZE;
   { // Test block operation
+    static constexpr auto BlockImpl = SetBlockAdaptor<kSize, Impl::block>;
     Buffers DstBuffer(kSize);
     for (uint8_t value : cpp::array<uint8_t, 3>{0, 1, 255}) {
       for (auto dst : DstBuffer.spans()) {
-        ASSERT_TRUE(CheckMemset<MemsetAdaptor<Impl>>(dst, value, kSize));
+        ASSERT_TRUE(CheckMemset<BlockImpl>(dst, value, kSize));
       }
     }
   }
   { // Test head tail operations from kSize to 2 * kSize.
+    static constexpr auto HeadTailImpl = SetAdaptor<Impl::head_tail>;
     Buffer DstBuffer(2 * kSize);
     for (size_t size = kSize; size < 2 * kSize; ++size) {
       const char value = size % 10;
       auto dst = DstBuffer.span().subspan(0, size);
-      ASSERT_TRUE(CheckMemset<Impl::head_tail>(dst, value, size));
+      ASSERT_TRUE(CheckMemset<HeadTailImpl>(dst, value, size));
     }
   }
   { // Test loop operations from kSize to 3 * kSize.
     if constexpr (kSize > 1) {
+      static constexpr auto LoopImpl = SetAdaptor<Impl::loop_and_tail>;
       Buffer DstBuffer(3 * kSize);
       for (size_t size = kSize; size < 3 * kSize; ++size) {
         const char value = size % 10;
         auto dst = DstBuffer.span().subspan(0, size);
-        ASSERT_TRUE((CheckMemset<Impl::loop_and_tail>(dst, value, size)));
+        ASSERT_TRUE((CheckMemset<LoopImpl>(dst, value, size)));
       }
     }
   }
 }
 
 using BcmpImplementations = testing::TypeList<
 #ifdef __SSE2__
     x86::sse2::Bcmp<16>,  //
#endif
     generic::Bcmp<1>,  //
     generic::Bcmp<2>,  //
     generic::Bcmp<4>,  //
     generic::Bcmp<16>, //
     generic::Bcmp<32>, //
     generic::Bcmp<64>  //
     >;
 
+// Adapt CheckBcmp signature to op implementation signatures.
 template <auto FnImpl>
-bool CheckBcmp(cpp::span<char> span1, cpp::span<char> span2, size_t size) {
-  assert(span1.size() == span2.size());
-  Copy(span2, span1);
-  // Compare equal
-  if (int cmp = (int)FnImpl(as_byte(span1), as_byte(span2), size); cmp != 0)
-    return false;
-  // Compare not equal if any byte differs
-  for (size_t i = 0; i < size; ++i) {
-    ++span2[i];
-    if (int cmp = (int)FnImpl(as_byte(span1), as_byte(span2), size); cmp == 0)
-      return false;
-    if (int cmp = (int)FnImpl(as_byte(span2), as_byte(span1), size); cmp == 0)
-      return false;
-    --span2[i];
-  }
-  return true;
-}
-
-template <typename T>
-static BcmpReturnType BcmpAdaptor(CPtr p1, CPtr p2, size_t size) {
-  assert(size == T::SIZE);
-  return T::block(p1, p2);
+int CmpAdaptor(cpp::span<char> p1, cpp::span<char> p2, size_t size) {
+  return (int)FnImpl(as_byte(p1), as_byte(p2), size);
+}
+template <size_t Size, auto FnImpl>
+int CmpBlockAdaptor(cpp::span<char> p1, cpp::span<char> p2, size_t size) {
+  assert(size == Size);
+  return (int)FnImpl(as_byte(p1), as_byte(p2));
 }
 
 TYPED_TEST(LlvmLibcOpTest, Bcmp, BcmpImplementations) {
   using Impl = ParamType;
   constexpr size_t kSize = Impl::SIZE;
   { // Test block operation
+    static constexpr auto BlockImpl = CmpBlockAdaptor<kSize, Impl::block>;
     Buffers Buffer1(kSize);
     Buffers Buffer2(kSize);
     for (auto span1 : Buffer1.spans()) {
       Randomize(span1);
       for (auto span2 : Buffer2.spans())
-        ASSERT_TRUE((CheckBcmp<BcmpAdaptor<Impl>>(span1, span2, kSize)));
+        ASSERT_TRUE((CheckBcmp<BlockImpl>(span1, span2, kSize)));
     }
   }
   { // Test head tail operations from kSize to 2 * kSize.
+    static constexpr auto HeadTailImpl = CmpAdaptor<Impl::head_tail>;
     Buffer Buffer1(2 * kSize);
     Buffer Buffer2(2 * kSize);
     Randomize(Buffer1.span());
     for (size_t size = kSize; size < 2 * kSize; ++size) {
       auto span1 = Buffer1.span().subspan(0, size);
       auto span2 = Buffer2.span().subspan(0, size);
-      ASSERT_TRUE((CheckBcmp<Impl::head_tail>(span1, span2, size)));
+      ASSERT_TRUE((CheckBcmp<HeadTailImpl>(span1, span2, size)));
     }
   }
   { // Test loop operations from kSize to 3 * kSize.
     if constexpr (kSize > 1) {
+      static constexpr auto LoopImpl = CmpAdaptor<Impl::loop_and_tail>;
       Buffer Buffer1(3 * kSize);
       Buffer Buffer2(3 * kSize);
       Randomize(Buffer1.span());
       for (size_t size = kSize; size < 3 * kSize; ++size) {
         auto span1 = Buffer1.span().subspan(0, size);
         auto span2 = Buffer2.span().subspan(0, size);
-        ASSERT_TRUE((CheckBcmp<Impl::loop_and_tail>(span1, span2, size)));
+        ASSERT_TRUE((CheckBcmp<LoopImpl>(span1, span2, size)));
       }
     }
   }
 }
 
 using MemcmpImplementations = testing::TypeList<
 #ifdef __SSE2__
     x86::sse2::Memcmp<16>,  //
#endif
     generic::Memcmp<2>,  //
     generic::Memcmp<3>,  //
     generic::Memcmp<4>,  //
     generic::Memcmp<16>, //
     generic::Memcmp<32>, //
     generic::Memcmp<64>  //
     >;
 
-template <auto FnImpl>
-bool CheckMemcmp(cpp::span<char> span1, cpp::span<char> span2, size_t size) {
-  assert(span1.size() == span2.size());
-  Copy(span2, span1);
-  // Compare equal
-  if (int cmp = (int)FnImpl(as_byte(span1), as_byte(span2), size); cmp != 0)
-    return false;
-  // Compare not equal if any byte differs
-  for (size_t i = 0; i < size; ++i) {
-    ++span2[i];
-    int ground_truth = __builtin_memcmp(span1.data(), span2.data(), size);
-    if (ground_truth > 0) {
-      if (int cmp = (int)FnImpl(as_byte(span1), as_byte(span2), size); cmp <= 0)
-        return false;
-      if (int cmp = (int)FnImpl(as_byte(span2), as_byte(span1), size); cmp >= 0)
-        return false;
-    } else {
-      if (int cmp = (int)FnImpl(as_byte(span1), as_byte(span2), size); cmp >= 0)
-        return false;
-      if (int cmp = (int)FnImpl(as_byte(span2), as_byte(span1), size); cmp <= 0)
-        return false;
-    }
-    --span2[i];
-  }
-  return true;
-}
-
-template <typename T>
-static MemcmpReturnType MemcmpAdaptor(CPtr p1, CPtr p2, size_t size) {
-  assert(size == T::SIZE);
-  return T::block(p1, p2);
-}
-
 TYPED_TEST(LlvmLibcOpTest, Memcmp, MemcmpImplementations) {
   using Impl = ParamType;
   constexpr size_t kSize = Impl::SIZE;
   { // Test block operation
+    static constexpr auto BlockImpl = CmpBlockAdaptor<kSize, Impl::block>;
     Buffers Buffer1(kSize);
     Buffers Buffer2(kSize);
     for (auto span1 : Buffer1.spans()) {
       Randomize(span1);
       for (auto span2 : Buffer2.spans())
-        ASSERT_TRUE((CheckMemcmp<MemcmpAdaptor<Impl>>(span1, span2, kSize)));
+        ASSERT_TRUE((CheckMemcmp<BlockImpl>(span1, span2, kSize)));
     }
   }
   { // Test head tail operations from kSize to 2 * kSize.
+    static constexpr auto HeadTailImpl = CmpAdaptor<Impl::head_tail>;
     Buffer Buffer1(2 * kSize);
     Buffer Buffer2(2 * kSize);
     Randomize(Buffer1.span());
     for (size_t size = kSize; size < 2 * kSize; ++size) {
       auto span1 = Buffer1.span().subspan(0, size);
       auto span2 = Buffer2.span().subspan(0, size);
-      ASSERT_TRUE((CheckMemcmp<Impl::head_tail>(span1, span2, size)));
+      ASSERT_TRUE((CheckMemcmp<HeadTailImpl>(span1, span2, size)));
     }
   }
   { // Test loop operations from kSize to 3 * kSize.
     if constexpr (kSize > 1) {
+      static constexpr auto LoopImpl = CmpAdaptor<Impl::loop_and_tail>;
       Buffer Buffer1(3 * kSize);
       Buffer Buffer2(3 * kSize);
       Randomize(Buffer1.span());
       for (size_t size = kSize; size < 3 * kSize; ++size) {
         auto span1 = Buffer1.span().subspan(0, size);
         auto span2 = Buffer2.span().subspan(0, size);
-        ASSERT_TRUE((CheckMemcmp<Impl::loop_and_tail>(span1, span2, size)));
+        ASSERT_TRUE((CheckMemcmp<LoopImpl>(span1, span2, size)));
       }
     }
   }
 }
 
 } // namespace __llvm_libc

libc/test/src/string/memset_test.cpp

 //===-- Unittests for memset ----------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-#include "src/__support/CPP/span.h"
+#include "memory_utils/memory_check_utils.h"
 #include "src/string/memset.h"
 #include "utils/UnitTest/Test.h"
 
-using __llvm_libc::cpp::array;
-using __llvm_libc::cpp::span;
-using Data = array<char, 2048>;
+namespace __llvm_libc {
 
-static const span<const char> k_deadcode("DEADC0DE", 8);
-
-// Returns a Data object filled with a repetition of `filler`.
-Data get_data(span<const char> filler) {
-  Data out;
-  for (size_t i = 0; i < out.size(); ++i)
-    out[i] = filler[i % filler.size()];
-  return out;
+// Adapt CheckMemset signature to op implementation signatures.
+template <auto FnImpl>
+void SetAdaptor(cpp::span<char> p1, uint8_t value, size_t size) {
+  FnImpl(p1.begin(), value, size);
 }
 
 TEST(LlvmLibcMemsetTest, Thorough) {
-  const Data dirty = get_data(k_deadcode);
-  for (int value = -1; value <= 1; ++value) {
-    for (size_t count = 0; count < 1024; ++count) {
-      for (size_t align = 0; align < 64; ++align) {
-        auto buffer = dirty;
-        void *const dst = &buffer[align];
-        void *const ret = __llvm_libc::memset(dst, value, count);
-        // Return value is `dst`.
-        ASSERT_EQ(ret, dst);
-        // Everything before copy is untouched.
-        for (size_t i = 0; i < align; ++i)
-          ASSERT_EQ(buffer[i], dirty[i]);
-        // Everything in between is copied.
-        for (size_t i = 0; i < count; ++i)
-          ASSERT_EQ(buffer[align + i], (char)value);
-        // Everything after copy is untouched.
-        for (size_t i = align + count; i < dirty.size(); ++i)
-          ASSERT_EQ(buffer[i], dirty[i]);
-      }
-    }
+  static constexpr size_t kSize = 1024;
+  static constexpr auto Impl = SetAdaptor<__llvm_libc::memset>;
+  Buffer DstBuffer(kSize);
+  for (size_t size = 0; size < kSize; ++size) {
+    const char value = size % 10;
+    auto dst = DstBuffer.span().subspan(0, size);
+    ASSERT_TRUE((CheckMemset<Impl>(dst, value, size)));
   }
 }
 
-// FIXME: Add tests with reads and writes on the boundary of a read/write
-// protected page to check we're not reading nor writing prior/past the allowed
-// regions.
+} // namespace __llvm_libc