[libc-commits] [libc] [libc] created fuzz test for sin function (PR #101411)

[via libc-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: None (RoseZhang03)

<details>
<summary>Changes</summary>

Verifies that sin function output is correct by comparing with MPFR
output. NaN and inf are not tested (as our output will vary compared to
MPFR), and signed zeroes are already tested in unit tests.


---
Full diff: https://github.com/llvm/llvm-project/pull/101411.diff


3 Files Affected:

- (modified) libc/fuzzing/CMakeLists.txt (+1-1) 
- (modified) libc/fuzzing/math/CMakeLists.txt (+9) 
- (added) libc/fuzzing/math/sin_fuzz.cpp (+40) 


``````````diff
diff --git a/libc/fuzzing/CMakeLists.txt b/libc/fuzzing/CMakeLists.txt
index 816691b4bd440..e2dcecca7f7df 100644
--- a/libc/fuzzing/CMakeLists.txt
+++ b/libc/fuzzing/CMakeLists.txt
@@ -3,7 +3,7 @@ add_custom_target(libc-fuzzer)
 
 add_subdirectory(__support)
 # TODO(#85680): Re-enable math fuzzing after headers are sorted out
-# add_subdirectory(math)
+add_subdirectory(math)
 add_subdirectory(stdlib)
 add_subdirectory(stdio)
 add_subdirectory(string)
diff --git a/libc/fuzzing/math/CMakeLists.txt b/libc/fuzzing/math/CMakeLists.txt
index 6990a04922a5c..ad163cc53eae3 100644
--- a/libc/fuzzing/math/CMakeLists.txt
+++ b/libc/fuzzing/math/CMakeLists.txt
@@ -61,3 +61,12 @@ add_libc_fuzzer(
     libc.src.math.nextafterf
     libc.src.math.nextafterl
 )
+
+add_libc_fuzzer(
+  sin_fuzz
+  NEED_MPFR
+  SRCS
+    sin_fuzz.cpp
+  DEPENDS
+    libc.src.math.sin
+)
diff --git a/libc/fuzzing/math/sin_fuzz.cpp b/libc/fuzzing/math/sin_fuzz.cpp
new file mode 100644
index 0000000000000..ee9eee5ae5bff
--- /dev/null
+++ b/libc/fuzzing/math/sin_fuzz.cpp
@@ -0,0 +1,40 @@
+//===-- sin_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 sin implementation.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/math/sin.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, 64);
+  mpfr_set_d(input, x, MPFR_RNDN);
+  int output = mpfr_sin(input, input, MPFR_RNDN);
+  mpfr_subnormalize(input, output, MPFR_RNDN);
+  double to_compare = mpfr_get_d(input, MPFR_RNDN);
+
+  double result = LIBC_NAMESPACE::sin(x);
+
+  if (result != to_compare)
+    __builtin_trap();
+
+  mpfr_clear(input);
+  return 0;
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/101411