[libc-commits] [libc] [libc] added cos function fuzzing test (PR #101556)

[via libc-commits]

https://github.com/RoseZhang03 created https://github.com/llvm/llvm-project/pull/101556

None

>From 9798abe445b750be9617a03ac7da180f78546105 Mon Sep 17 00:00:00 2001
From: Rose Zhang <rosezhang at google.com>
Date: Thu, 1 Aug 2024 20:26:34 +0000
Subject: [PATCH] [libc] added cos function fuzzing test

---
 libc/fuzzing/math/CMakeLists.txt |  9 +++++++
 libc/fuzzing/math/cos_fuzz.cpp   | 40 ++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)
 create mode 100644 libc/fuzzing/math/cos_fuzz.cpp

diff --git a/libc/fuzzing/math/CMakeLists.txt b/libc/fuzzing/math/CMakeLists.txt
index ad163cc53eae3..7faf8fd53c849 100644
--- a/libc/fuzzing/math/CMakeLists.txt
+++ b/libc/fuzzing/math/CMakeLists.txt
@@ -70,3 +70,12 @@ add_libc_fuzzer(
   DEPENDS
     libc.src.math.sin
 )
+
+add_libc_fuzzer(
+  cos_fuzz
+  NEED_MPFR
+  SRCS
+    cos_fuzz.cpp
+  DEPENDS
+    libc.src.math.cos
+)
diff --git a/libc/fuzzing/math/cos_fuzz.cpp b/libc/fuzzing/math/cos_fuzz.cpp
new file mode 100644
index 0000000000000..f961a17e7f203
--- /dev/null
+++ b/libc/fuzzing/math/cos_fuzz.cpp
@@ -0,0 +1,40 @@
+//===-- cos_fuzz.cpp ----------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// Fuzzing test for llvm-libc cos implementation.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/math/cos.h"
+#include <cmath>
+#include <mpfr.h>
+
+extern "C" int LLVMFuzzerTestOneInput(const double x) {
+  // remove NaN and inf as preconditions
+  if (std::isnan(x))
+    return 0;
+  if (std::isinf(x))
+    return 0;
+  // signed zeros already tested in unit tests
+  if (std::signbit(x) && x == 0.0)
+    return 0;
+  mpfr_t input;
+  mpfr_init2(input, 53);
+  mpfr_set_d(input, x, MPFR_RNDN);
+  int output = mpfr_cos(input, input, MPFR_RNDN);
+  mpfr_subnormalize(input, output, MPFR_RNDN);
+  double to_compare = mpfr_get_d(input, MPFR_RNDN);
+
+  double result = LIBC_NAMESPACE::cos(x);
+
+  if (result != to_compare)
+    __builtin_trap();
+
+  mpfr_clear(input);
+  return 0;
+}