[libc-commits] [libc] [libc] sincos fuzz test (PR #147855)

[via libc-commits]

https://github.com/sribee8 created https://github.com/llvm/llvm-project/pull/147855

Created fuzz test for sincos

>From b72d9bb1eb65ecf993fcef2052bec15b336363d8 Mon Sep 17 00:00:00 2001
From: Sriya Pratipati <sriyap at google.com>
Date: Wed, 9 Jul 2025 23:45:32 +0000
Subject: [PATCH 1/2] sincos fuzz test

---
 libc/fuzzing/math/CMakeLists.txt  |  9 ++++++
 libc/fuzzing/math/sincos_fuzz.cpp | 49 +++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 libc/fuzzing/math/sincos_fuzz.cpp

diff --git a/libc/fuzzing/math/CMakeLists.txt b/libc/fuzzing/math/CMakeLists.txt
index 31336fa3e49f3..d8df31e87a648 100644
--- a/libc/fuzzing/math/CMakeLists.txt
+++ b/libc/fuzzing/math/CMakeLists.txt
@@ -88,3 +88,12 @@ add_libc_fuzzer(
   DEPENDS
     libc.src.math.tan
 )
+
+add_libc_fuzzer(
+  sincos_fuzz
+  NEED_MPFR
+  SRCS
+    sincos_fuzz.cpp
+  DEPENDS
+    libc.src.math.sincos
+)
diff --git a/libc/fuzzing/math/sincos_fuzz.cpp b/libc/fuzzing/math/sincos_fuzz.cpp
new file mode 100644
index 0000000000000..d6cc6612b60d8
--- /dev/null
+++ b/libc/fuzzing/math/sincos_fuzz.cpp
@@ -0,0 +1,49 @@
+//===-- sincos_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/sincos.h"
+#include "utils/MPFRWrapper/mpfr_inc.h"
+#include <math.h>
+
+extern "C" int LLVMFuzzerTestOneInput(double x) {
+  // remove NaN and inf as preconditions
+  if (isnan(x) || isinf(x))
+    return 0;
+  // signed zeros already tested in unit tests
+  if (signbit(x) && x == 0.0)
+    return 0;
+  mpfr_t input;
+  mpfr_t sin_x;
+  mpfr_t cos_x;
+
+  mpfr_init2(input, 53);
+  mpfr_init2(sin_x, 53);
+  mpfr_init2(cos_x, 53);
+
+  mpfr_set_d(input, x, MPFR_RNDN);
+
+  int output = mpfr_sin_cos(sin_x, cos_x, input, MPFR_RNDN);
+  mpfr_subnormalize(sin_x, output, MPFR_RNDN);
+  mpfr_subnormalize(cos_x, output, MPFR_RNDN);
+
+  double to_compare_sin = mpfr_get_d(sin_x, MPFR_RNDN);
+  double to_compare_cos = mpfr_get_d(cos_x, MPFR_RNDN);
+
+  double sin_res, cos_res;
+  LIBC_NAMESPACE::sincos(x, &sin_res, &cos_res);
+
+  if (sin_res != to_compare_sin || cos_res != to_compare_cos)
+    __builtin_trap();
+
+  mpfr_clear(input);
+  return 0;
+}

>From 9b3ea90fd443b8ddc6f41c82a5b2ee942797e595 Mon Sep 17 00:00:00 2001
From: Sriya Pratipati <sriyap at google.com>
Date: Wed, 9 Jul 2025 23:52:27 +0000
Subject: [PATCH 2/2] fixed memory issues

---
 libc/fuzzing/math/sincos_fuzz.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libc/fuzzing/math/sincos_fuzz.cpp b/libc/fuzzing/math/sincos_fuzz.cpp
index d6cc6612b60d8..8cc6f7291a3df 100644
--- a/libc/fuzzing/math/sincos_fuzz.cpp
+++ b/libc/fuzzing/math/sincos_fuzz.cpp
@@ -45,5 +45,7 @@ extern "C" int LLVMFuzzerTestOneInput(double x) {
     __builtin_trap();
 
   mpfr_clear(input);
+  mpfr_clear(sin_x);
+  mpfr_clear(cos_x);
   return 0;
 }