libc/test/src/stdio/snprintf_test.cpp

//===-- Unittests for snprintf --------------------------------------------===//
//
// 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/stdio/snprintf.h"

#include "test/UnitTest/ErrnoCheckingTest.h"
#include "test/UnitTest/ErrnoSetterMatcher.h"
#include "test/UnitTest/Test.h"

using LlvmLibcSNPrintfTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;

// The sprintf test cases cover testing the shared printf functionality, so
// these tests will focus on snprintf exclusive features.

TEST(LlvmLibcSNPrintfTest, CutOff) {
  char buff[100];
  int written;

  written = LIBC_NAMESPACE::snprintf(buff, 16,
                                     "A simple string with no conversions.");
  EXPECT_EQ(written, 36);
  ASSERT_STREQ(buff, "A simple string");

  written = LIBC_NAMESPACE::snprintf(buff, 5, "%s", "1234567890");
  EXPECT_EQ(written, 10);
  ASSERT_STREQ(buff, "1234");

  written = LIBC_NAMESPACE::snprintf(buff, 67, "%-101c", 'a');
  EXPECT_EQ(written, 101);
  ASSERT_STREQ(buff, "a "
                     "        " // Each of these is 8 spaces, and there are 8.
                     "        " // In total there are 65 spaces
                     "        " // 'a' + 65 spaces + '\0' = 67
                     "        "
                     "        "
                     "        "
                     "        "
                     "        ");

  // passing null as the output pointer is allowed as long as buffsz is 0.
  written = LIBC_NAMESPACE::snprintf(nullptr, 0, "%s and more", "1234567890");
  EXPECT_EQ(written, 19);

  written = LIBC_NAMESPACE::snprintf(nullptr, 0, "%*s", INT_MIN, "nothing");
  EXPECT_EQ(written, INT_MAX);
}

TEST(LlvmLibcSNPrintfTest, NoCutOff) {
  char buff[64];
  int written;

  written = LIBC_NAMESPACE::snprintf(buff, 37,
                                     "A simple string with no conversions.");
  EXPECT_EQ(written, 36);
  ASSERT_STREQ(buff, "A simple string with no conversions.");

  written = LIBC_NAMESPACE::snprintf(buff, 20, "%s", "1234567890");
  EXPECT_EQ(written, 10);
  ASSERT_STREQ(buff, "1234567890");
}

TEST(LlvmLibcSNPrintfTest, CharsWrittenOverflow) {
  char buff[0];

  // Trigger an overflow in the return value of snprintf by writing more than
  // INT_MAX bytes.
  int int_max = LIBC_NAMESPACE::cpp::numeric_limits<int>::max();
  int written = LIBC_NAMESPACE::snprintf(buff, 0, "%*stest", int_max, "");
  EXPECT_LT(written, 0);
  ASSERT_ERRNO_FAILURE();
}