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Notes on C/C++

C++14 in CMakeLists.txt

Add after the project definition:

# C++14
set(CMAKE_CXX_STANDARD 14)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

AddressSanitizer for memory leak detection

Add these flags after the project definition:

# -fsanitize=address for AddressSanitizer memory leak reporting
# -g for debugging info
# -O1 for basic optimizations -- can help with more complicated asan reporting
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=address -g -O1")

Then when you run an app with a memory leak:

./myapp

Hello, world!

=================================================================
==22602==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 40 byte(s) in 1 object(s) allocated from:
    #0 0x7f59e8282608 in operator new[](unsigned long) (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xe0608)
    #1 0x55b5db085595 in SimpleContainer::SimpleContainer(int) /path/to/src/hw/hw.h:14
    #2 0x55b5db085595 in main /path/to/src/hw/main.cpp:17
    #3 0x55b5db0858a3 in _IO_stdin_used (/path/to/src/hw/build/hw+0x18a3)

SUMMARY: AddressSanitizer: 40 byte(s) leaked in 1 allocation(s).

Testing with Googletest

References:

Assertions

A subset:

  • EXPECT_TRUE(<expr>) - Test <expr> and report pass/fail.
  • ASSERT_TRUE(<expr>) - Test <expr> and report pass/fail, stopping the tests if it fails.
  • EXPECT_EQ(<expr1>, <expr2>) - Test whether <expr1> and <expr2> are equal.
  • EXPECT_NE(<expr1>, <expr2>) - Test whether <expr1> and <expr2> differ.
  • EXPECT_STREQ(s1, s2) - Test whether two C strings have the same content.
  • EXPECT_FLOAT_EQ(<expr1>, <expr2>) - Test whether <expr1> and <expr2> are equal using floating point comparison. ...

To provide a custom failure message, stream it into the macro:

EXPECT_EQ(x, y) << "x and y should be the same";

To use the comparison expects/assertions (EXPECT_EQ, ASSERT_EQ, etc) with a custom type, define the necessary comparison operator(s) (== or <).

Test Fixtures

A fixture class to test class Foo should be named FooTest and should inherit from ::testing::Test, with protected access. Use SetUp to initialize (use override to be sure it's not misspelled):

class FooTest : public ::testing::Test {
  protected:
    void SetUp() override {
      x = 123;
      y = 456;
    }

    int x;
    int y;
};

Setup the project:

mkdir example
cd example
git clone https://github.com/google/googletest.git

Edit CMakeLists.txt, example:

cmake_minimum_required (VERSION 3.10)
set(This example)
project ($(This) C CXX)
set(CMAKE_C_STANDARD 99)
set(CMAKE_CXX_STANDARD 14)
#set(CMAKE_CXX_STANDARD_REQUIRED ON)
#set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Wpedantic")
# Library
set(CMAKE_POSITION_INDEPENDENT_CODE ON)

enable_testing()
add_subdirectory(googletest)

set(Headers
  example.hpp
)

set(Sources
  example.cpp
)

add_library(${This} STATIC ${Sources} ${Headers})
add_subdirectory(test)

Add a test skeleton

Add a test dir and a blank test:

mkdir test
touch example_tests.cpp

Add a test/CMakeLists.txt file:

cmake_minimum_required (VERSION 3.10)
set(This example_tests)
project ($(This) C CXX)

set(Sources
  example_tests.cpp
)

add_executable(${This} ${Sources})
target_link_libraries(${This} PUBLIC
  gtest_main
  example
)

add_test(
  NAME ${This}
  COMMAND ${This}
)

Build

Build:

mkdir build
cd build
cmake ..

This may remove a warning -- edit CMakeCache.txt and set gtest_force_shared_crt to ON:

gtest_force_shared_crt:BOOL=ON

Then do a clean build:

make clean
make

Run tests

Run an empty test (from the build/ dir):

./test/example_tests

Running main() from /home/andy/src/example/googletest/googletest/src/gtest_main.cc
[==========] Running 0 tests from 0 test suites.
[==========] 0 tests from 0 test suites ran. (0 ms total)
[  PASSED  ] 0 tests.

Dummy test

Add a dummy test to test/example_tests.cpp:

#include <gtest/gtest.h>

TEST(example_tests, dummy_test) {
  EXPECT_TRUE(true);
}

Run tests

Run the tests again:

./test/example_tests

Running main() from /home/andy/src/example/googletest/googletest/src/gtest_main.cc
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from example_tests
[ RUN      ] example_tests.dummy_test
[       OK ] example_tests.dummy_test (0 ms)
[----------] 1 test from example_tests (0 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test suite ran. (0 ms total)
[  PASSED  ] 1 test.

Or:

make test

Running tests...
Test project /home/andy/src/example/build
    Start 1: example_tests
1/1 Test #1: example_tests ....................   Passed    0.00 sec

100% tests passed, 0 tests failed out of 1

Total Test time (real) =   0.00 sec

Run a specific test case

./tests/example_tests --gtest_filter=Example.SomeTest

String processing

Building up strings

std::to_string (reference is useful for building up strings from other data types:

int x = 4;
std::string s = "This is a string " + "made from " + std::to_string(x) + " parts.";