[libc-commits] [PATCH] D151336: [libc] simplify test for getrandom

[Guillaume Chatelet via Phabricator via libc-commits]

gchatelet updated this revision to Diff 525180.
gchatelet marked an inline comment as done.
gchatelet added a comment.

- Remove redundant reset of libc_errno


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D151336/new/

https://reviews.llvm.org/D151336

Files:
  libc/test/src/sys/random/linux/getrandom_test.cpp


Index: libc/test/src/sys/random/linux/getrandom_test.cpp
===================================================================
--- libc/test/src/sys/random/linux/getrandom_test.cpp
+++ libc/test/src/sys/random/linux/getrandom_test.cpp
@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "src/__support/CPP/array.h"
 #include "src/errno/libc_errno.h"
 #include "src/math/fabs.h"
 #include "src/sys/random/getrandom.h"
@@ -13,53 +14,41 @@
 #include "test/UnitTest/Test.h"
 
 TEST(LlvmLibcGetRandomTest, InvalidFlag) {
-  using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
-  static constexpr size_t SIZE = 256;
-  char data[SIZE];
-  libc_errno = 0;
-  ASSERT_THAT(__llvm_libc::getrandom(data, SIZE, -1), Fails(EINVAL));
+  __llvm_libc::cpp::array<char, 10> buffer;
   libc_errno = 0;
+  ASSERT_THAT(__llvm_libc::getrandom(buffer.data(), buffer.size(), -1),
+              __llvm_libc::testing::ErrnoSetterMatcher::Fails(EINVAL));
 }
 
 TEST(LlvmLibcGetRandomTest, InvalidBuffer) {
-  using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
-
-  libc_errno = 0;
-  ASSERT_THAT(__llvm_libc::getrandom(nullptr, 65536, 0), Fails(EFAULT));
   libc_errno = 0;
+  ASSERT_THAT(__llvm_libc::getrandom(nullptr, 65536, 0),
+              __llvm_libc::testing::ErrnoSetterMatcher::Fails(EFAULT));
 }
 
 TEST(LlvmLibcGetRandomTest, ReturnsSize) {
-  static constexpr size_t SIZE = 8192;
-  uint8_t buf[SIZE];
-  for (size_t i = 0; i < SIZE; ++i) {
+  __llvm_libc::cpp::array<char, 10> buffer;
+  for (size_t i = 0; i < buffer.size(); ++i) {
     // Without GRND_RANDOM set this should never fail.
-    ASSERT_EQ(__llvm_libc::getrandom(buf, i, 0), static_cast<ssize_t>(i));
+    ASSERT_EQ(__llvm_libc::getrandom(buffer.data(), i, 0),
+              static_cast<ssize_t>(i));
   }
 }
 
-TEST(LlvmLibcGetRandomTest, PiEstimation) {
-  static constexpr size_t LIMIT = 10000000;
-  static constexpr double PI = 3.14159265358979;
+TEST(LlvmLibcGetRandomTest, CheckValue) {
+  // Probability of picking one particular value amongst 256 possibilities a
+  // hundred times in a row is (1/256)^100 = 1.49969681e-241.
+  __llvm_libc::cpp::array<char, 100> buffer;
 
-  auto generator = []() {
-    uint16_t data;
-    __llvm_libc::getrandom(&data, sizeof(data), 0);
-    return data;
-  };
+  for (char &c : buffer)
+    c = 0;
 
-  auto sample = [&]() {
-    auto x = static_cast<double>(generator()) / 65536.0;
-    auto y = static_cast<double>(generator()) / 65536.0;
-    return x * x + y * y < 1.0;
-  };
+  __llvm_libc::getrandom(buffer.data(), buffer.size(), 0);
 
-  double counter = 0;
-  for (size_t i = 0; i < LIMIT; ++i) {
-    if (sample()) {
-      counter += 1.0;
-    }
-  }
-  counter = counter / LIMIT * 4.0;
-  ASSERT_TRUE(__llvm_libc::fabs(counter - PI) < 0.1);
+  bool all_zeros = true;
+  for (char c : buffer)
+    if (c != 0)
+      all_zeros = false;
+
+  ASSERT_FALSE(all_zeros);
 }


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