libassert

Table of Contents:

• 30-Second Overview
  • CMake FetchContent Usage
• Philosophy
• Features
  • Custom Failure Handlers
  • Smart literal formatting
  • Integrations with Catch2 and GoogleTest
• Methodology
• Considerations
• In-Depth Library Documentation
  • Assertion Macros
    • Parameters
    • Return value
  • General Utilities
  • Terminal Utilities
  • Configuration
  • Assertion information
    • Anatomy of Assertion Information
  • Stringification of Custom Objects
  • Custom Failure Handlers
  • Breakpoints
  • Other Configurations
• Integration with Test Libraries
  • Catch2
  • GoogleTest
• Usage
  • CMake FetchContent
  • System-Wide Installation
  • Local User Installation
  • Use Without CMake
  • Package Managers
    • Conan
    • Vcpkg
• Platform Logistics
• Replacing <cassert>
• FAQ
• Cool projects using libassert
• Comparison With Other Languages

30-Second Overview

Library philosophy: Provide as much helpful diagnostic info as possible.

Some of the awesome things the library does:

void zoog(const std::map<std::string, int>& map) {
    DEBUG_ASSERT(map.contains("foo"), "expected key not found", map);
}

ASSERT(vec.size() > min_items(), "vector doesn't have enough items", vec);

std::optional<float> get_param();
float f = *ASSERT_VAL(get_param());

Types of assertions:

Conditional assertions:

• DEBUG_ASSERT: Checked in debug but but does nothing in release (analogous to the standard library's assert)
• ASSERT: Checked in both debug and release
• ASSUME: Checked in debug and serves as an optimization hint in release

Unconditional assertions:

• PANIC: Triggers in both debug and release
• UNREACHABLE: Triggers in debug, marked as unreachable in release

Prefer lowecase assert?

You can enable the lowercase debug_assert and assert aliases with -DLIBASSERT_LOWERCASE.

Summary of features:

• Automatic decomposition of assertion expressions without macros such as ASSERT_EQ etc.
• Assertion messages
• Arbitrary extra diagnostics
• Syntax highlighting
• Stack traces
• DEBUG_ASSERT_VAL and ASSERT_VAL variants that return a value so they can be integrated seamlessly into code, e.g. FILE* f = ASSERT_VAL(fopen(path, "r") != nullptr)
• Smart literal formatting
• Stringification of user-defined types
• Custom failure handlers
• Catch2/Gtest integrations
• {fmt} support
• Programatic breakpoints on assertion failures for more debugger-friendly assertions, more info below

CMake FetchContent Usage

include(FetchContent)
FetchContent_Declare(
  libassert
  GIT_REPOSITORY https://github.com/jeremy-rifkin/libassert.git
  GIT_TAG        v2.1.2 # <HASH or TAG>
)
FetchContent_MakeAvailable(libassert)
target_link_libraries(your_target libassert::assert)

# On windows copy libassert.dll to the same directory as the executable for your_target
if(WIN32)
  add_custom_command(
    TARGET your_target POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E copy_if_different
    $<TARGET_FILE:libassert::assert>
    $<TARGET_FILE_DIR:your_target>
  )
endif()

Be sure to configure with -DCMAKE_BUILD_TYPE=Debug or -DDCMAKE_BUILD_TYPE=RelWithDebInfo for symbols and line information.

On macOS it is recommended to generate a .dSYM file, see Platform Logistics below.

For other ways to use the library, such as through package managers or a system-wide installation, see Usage below.

Philosophy

Fundamentally the role of assertions is to verify assumptions made in software and identify violations close to their sources. Assertion tooling should prioritize providing as much information and context to the developer as possible to allow for speedy triage. Unfortunately, existing language and library tooling provides very limited triage information.

For example with stdlib assertions an assertion such as assert(n <= 12); provides no information upon failure about why it failed or what lead to its failure. Providing a stack trace and the value of n greatley improves triage and debugging. Ideally an assertion failure should provide enough diagnostic information that the programmmer doesn't have to rerun in a debugger to pinpoint the problem.

Version 1 of this library was an exploration looking at how much helpful information and functionality could be packed into assertions while also providing a quick and easy interface for the developer.

Version 2 of this library takes lessons learned from version 1 to create a tool that I personally have found indispensable in development.

Features

Automatic Expression Decomposition

The most important feature this library supports is automatic expression decomposition. No need for ASSERT_LT or other such hassle, assert(vec.size() > 10); is automatically understood, as showcased above.

Expression Diagnostics

Values involved in assert expressions are displayed. Redundant diagnostics like 2 => 2 are avoided.

DEBUG_ASSERT(map.count(1) == 2);

Only the full assert expression is able to be extracted from a macro call. Showing which parts of the expression correspond to what values requires some basic expression parsing. C++ grammar is ambiguous but most expressions can be disambiguated.

Extra Diagnostics

All assertions in this library support optional diagnostic messages as well as arbitrary other diagnostic messages.

FILE* f = ASSERT_VAL(fopen(path, "r") != nullptr, "Internal error with foobars", errno, path);

Special handling is provided for errno, and strerror is automatically called.

Note: Extra diagnostics are only evaluated in the failure path of an assertion.

Stack Traces

A lot of work has been put into generating pretty stack traces and formatting them as nicely as possible. Cpptrace is used as a portable and self-contained solution for stacktraces pre-C++23. Optional configurations can be found in the library's documentation.

One feature worth noting is that instead of always printing full paths, only the minimum number of directories needed to differentiate paths are printed.

Another feature worth pointing out is that the stack traces will fold traces with deep recursion:

Syntax Highlighting

The assertion handler applies syntax highlighting wherever appropriate, as seen in all the screenshots above. This is to help enhance readability.

Custom Failure Handlers

Libassert supports custom assertion failure handlers:

void handler(assert_type type, const assertion_info& assertion) {
    throw std::runtime_error("Assertion failed:\n" + assertion.to_string());
}

int main() {
    libassert::set_failure_handler(handler);
}

Debug Stringification

A lot of care is given to producing debug stringifications of values as effectively as possible: Strings, characters, numbers, should all be printed as you'd expect. Additionally containers, tuples, std::optional, smart pointers, etc. are all stringified to show as much information as possible. If a user defined type overloads operator<<(std::ostream& o, const S& s), that overload will be called. Otherwise it a default message will be printed. Additionally, a stringification customiztaion point is provided:

template<> struct libassert::stringifier<MyObject> {
    std::string stringify(const MyObject& type) {
        return ...;
    }
};

Smart literal formatting

Assertion values are printed in hex or binary as well as decimal if hex/binary are used on either side of an assertion expression:

ASSERT(get_mask() == 0b00001101);

Safe Comparisons

Because expressions are already being automatically decomposed, you can opt into having signed-unsigned comparisons done automatically done with sign safety with -DLIBASSERT_SAFE_COMPARISONS:

ASSERT(18446744073709551606ULL == -10);

Integrations with Catch2 and GoogleTest

Libassert provides two headers <libassert/assert-catch2.hpp> and <libassert/assert-gtest.hpp> for use with catch2 and GoogleTest.

Example output from gtest:

More information below.

Methodology

Libassert provides three types of assertions, each varying slightly depending on when it should be checked and how it should be interpreted:

Name	Effect
DEBUG_ASSERT	Checked in debug, no codegen in release
ASSERT	Checked in both debug and release builds
ASSUME	Checked in debug, if(!(expr)) { __builtin_unreachable(); } in release

Unconditional assertions

Name	Effect
PANIC	Triggers in both debug and release
UNREACHABLE	Triggered in debug, marked as unreachable in release.

One benefit to PANIC and UNREACHABLE over ASSERT(false, ...) is that the compiler gets [[noreturn]] information.

ASSUME marks the fail path as unreachable in release, potentially providing helpful information to the optimizer. This isn't the default behavior for all assertions because the immediate consequence of this is that assertion failure in -DNDEBUG can lead to UB and it's better to make this very explicit.

Assertion variants that can be used in-line in an expression, such as FILE* file = ASSERT_VAL(fopen(path, "r"), "Failed to open file");, are also available:

Name	Effect
DEBUG_ASSERT_VAL	Checked in debug, must be evaluated in both debug and release
ASSERT_VAl	Checked in both debug and release builds
ASSUME_VAL	Checked in debug, if(!(expr)) { __builtin_unreachable(); } in release

Note: Even in release builds the expression for DEBUG_ASSERT_VAL must still be evaluated, unlike DEBUG_ASSERT. Of course, if the result is unused and produces no side effects it will be optimized away.

Considerations

Performance: As far as runtime performance goes, the impact at callsites is very minimal under -Og or higher. The fast-path in the code (i.e., where the assertion does not fail), will be fast. A lot of work is required to process assertion failures once they happen. However, since failures should be rare, this should not matter.

Compile speeds:, there is a compile-time cost associated with all the template instantiations required for this library's magic.

Other:

[!NOTE] Because of expression decomposition, ASSERT(1 = 2); compiles.

In-Depth Library Documentation

Assertion Macros

All assertion functions are macros. Here are some pseudo-declarations for interfacing with them:

void DEBUG_ASSERT              (expression, [optional message], [optional extra diagnostics, ...]);
void ASSERT                    (expression, [optional message], [optional extra diagnostics, ...]);
void ASSUME                    (expression, [optional message], [optional extra diagnostics, ...]);
decltype(auto) DEBUG_ASSERT_VAL(expression, [optional message], [optional extra diagnostics, ...]);
decltype(auto) ASSERT_VAL      (expression, [optional message], [optional extra diagnostics, ...]);
decltype(auto) ASSUME_VAL      (expression, [optional message], [optional extra diagnostics, ...]);

void PANIC      ([optional message], [optional extra diagnostics, ...]);
void UNREACHABLE([optional message], [optional extra diagnostics, ...]);

-DLIBASSERT_PREFIX_ASSERTIONS can be used to prefix these macros with LIBASSERT_. This is useful for wrapping libassert assertions.

-DLIBASSERT_LOWERCASE can be used to enable the debug_assert and assert aliases for DEBUG_ASSERT and ASSERT. See: Replacing <cassert>.

Parameters

expression

The expression is automatically decomposed so diagnostic information can be provided. The resultant type must be convertible to boolean.

The operation between left and right hand sides of the top-level operation in the expression tree is evaluated by a function object.

Note: Boolean logical operators (&& and ||) are not decomposed by default due to short circuiting.

assertion message

An optional assertion message may be provided. If the first argument following the assertion expression, or the first argument in PANIC/UNREACHABLE, is any string type it will be used as the message (if you want the first parameter, which happens to be a string, to be an extra diagnostic value instead simply pass an empty string first, i.e. ASSERT(foo, "", str);).

Note: The assertion message expression is only evaluated in the failure path of the assertion.

extra diagnostics

An arbitrary number of extra diagnostic values may be provided. These are displayed below the expression diagnostics if a check fails.

Note: Extra diagnostics are only evaluated in the failure path of the assertion.

There is special handling when errno is provided: The value of strerror is displayed automatically.

Return value

To facilitate ease of integration into code _VAL variants are provided which return a value from the assert expression. The returned value is determined as follows:

• If there is no top-level binary operation (e.g. as in ASSERT_VAL(foo()); or ASSERT_VAL(false);) in the assertion expression, the value of the expression is simply returned.
• Otherwise if the top-level binary operation is ==, !=, <, <=, >, >=, &&, ||, or or any assignment or compound assignment then the value of the left-hand operand is returned.
• Otherwise if the top-level binary operation is &, |, ^, <<, >>, or any binary operator with precedence above bitshift then value of the whole expression is returned.

I.e., ASSERT_VAL(foo() > 2); returns the computed result from foo() and ASSERT_VAL(x & y); returns the computed result of x & y;

If the value from the assertion expression selected to be returned is an lvalue, the type of the assertion call will be an lvalue reference. If the value from the assertion expression is an rvalue then the type of the call will be an rvalue.

General Utilities

namespace libassert {
    [[nodiscard]] std::string stacktrace(
        int width = 0,
        const color_scheme& scheme = get_color_scheme(),
        std::size_t skip = 0
    );
    template<typename T> [[nodiscard]] std::string_view type_name() noexcept;
    template<typename T> [[nodiscard]] std::string pretty_type_name() noexcept;
    template<typename T> [[nodiscard]] std::string stringify(const T& value);
}

• stacktrace: Generates a stack trace, formats to the given width (0 for no width formatting)
• type_name: Returns the type name of T
• pretty_type_name: Returns the prettified type name for T
• stringify: Produces a debug stringification of a value

Terminal Utilities

namespace libassert {
    void enable_virtual_terminal_processing_if_needed();
    inline constexpr int stdin_fileno = 0;
    inline constexpr int stdout_fileno = 1;
    inline constexpr int stderr_fileno = 2;
    bool isatty(int fd);
    [[nodiscard]] int terminal_width(int fd);
}

• enable_virtual_terminal_processing_if_needed: Enable ANSI escape sequences for terminals on windows, needed for color output.
• isatty: Returns true if the file descriptor corresponds to a terminal
• terminal_width: Returns the width of the terminal represented by fd or 0 on error

Configuration

Color Scheme:

namespace libassert {
    // NOTE: string view underlying data should have static storage duration, or otherwise live as
    // long as the scheme is in use
    struct color_scheme {
        std::string_view string, escape, keyword, named_literal, number, punctuation, operator_token,
                    call_identifier, scope_resolution_identifier, identifier, accent, unknown, reset;
        static const color_scheme ansi_basic;
        static const color_scheme ansi_rgb;
        static const color_scheme blank;
    };
    void set_color_scheme(const color_scheme&);
    const color_scheme& get_color_scheme();
}

By default color_scheme::ansi_rgb is used. To disable colors, use color_scheme::blank.

• set_color_scheme: Sets the color scheme for the default assertion handler when stderr is a terminal

Separator:

namespace libassert {
    void set_separator(std::string_view separator);
}

• set_separator: Sets the separator between expression and value in assertion diagnostic output. Default: =>. NOTE: Not thread-safe.

Literal formatting mode:

namespace libassert {
    enum class literal_format_mode {
        infer, // infer literal formats based on the assertion condition
        no_variations, // don't do any literal format variations, just default
        fixed_variations // always use a fixed set of formats (in addition to the default format)
    };
    void set_literal_format_mode(literal_format_mode);

    enum class literal_format : unsigned {
        // integers and floats are decimal by default, chars are of course chars, and everything
        // else only has one format that makes sense
        default_format = 0,
        integer_hex = 1,
        integer_octal = 2,
        integer_binary = 4,
        integer_character = 8, // format integers as characters and characters as integers
        float_hex = 16,
    };
    [[nodiscard]] constexpr literal_format operator|(literal_format a, literal_format b);
    void set_fixed_literal_format(literal_format);
}

• set_literal_format_mode: Sets whether the library should show literal variations or infer them
• set_fixed_literal_format: Set a fixed literal format configuration, automatically changes the literal_format_mode; note that the default format will always be used along with others

Path mode:

namespace libassert {
    enum class path_mode {
        full, // full path is used
        disambiguated, // only enough folders needed to disambiguate are provided
        basename, // only the file name is used
    };
    LIBASSERT_EXPORT void set_path_mode(path_mode mode);
}

• set_path_mode: Sets the path shortening mode for assertion output. Default: path_mode::disambiguated.

Assertion information

namespace libassert {
    enum class assert_type {
        debug_assertion,
        assertion,
        assumption,
        panic,
        unreachable
    };

    struct LIBASSERT_EXPORT binary_diagnostics_descriptor {
        std::string left_expression;
        std::string right_expression;
        std::string left_stringification;
        std::string right_stringification;
    };

    struct extra_diagnostic {
        std::string_view expression;
        std::string stringification;
    };

    struct LIBASSERT_EXPORT assertion_info {
        std::string_view macro_name;
        assert_type type;
        std::string_view expression_string;
        std::string_view file_name;
        std::uint32_t line;
        std::string_view function;
        std::optional<std::string> message;
        std::optional<binary_diagnostics_descriptor> binary_diagnostics;
        std::vector<extra_diagnostic> extra_diagnostics;
        size_t n_args;

        std::string_view action() const;

        const cpptrace::raw_trace& get_raw_trace() const;
        const cpptrace::stacktrace& get_stacktrace() const;

        [[nodiscard]] std::string header(int width = 0, const color_scheme& scheme = get_color_scheme()) const;
        [[nodiscard]] std::string tagline(const color_scheme& scheme = get_color_scheme()) const;
        [[nodiscard]] std::string location() const;
        [[nodiscard]] std::string statement(const color_scheme& scheme = get_color_scheme()) const;
        [[nodiscard]] std::string print_binary_diagnostics(int width = 0, const color_scheme& scheme = get_color_scheme()) const;
        [[nodiscard]] std::string print_extra_diagnostics(int width = 0, const color_scheme& scheme = get_color_scheme()) const;
        [[nodiscard]] std::string print_stacktrace(int width = 0, const color_scheme& scheme = get_color_scheme()) const;

        [[nodiscard]] std::string to_string(int width = 0, const color_scheme& scheme = get_color_scheme()) const;
    };
}

Anatomy of Assertion Information

Debug Assertion failed at demo.cpp:194: void foo::baz(): Internal error with foobars
    debug_assert(open(path, 0) >= 0, ...);
    Where:
        open(path, 0) => -1
    Extra diagnostics:
        errno =>  2 "No such file or directory"
        path  => "/home/foobar/baz"

Stack trace:
#1 demo.cpp:194 foo::baz()
#2 demo.cpp:172 void foo::bar<int>(std::pair<int, int>)
#3 demo.cpp:396 main

• Debug Assertion failed: assertion_info.action()
• demo.cpp:194: assertion_info.file_name and assertion_info.line
• void foo::baz(): assertion_info.pretty_function
• Internal error with foobars: assertion_info.message
• debug_assert: assertion_info.macro_name
• open(path, 0) >= 0: assertion_info.expression_string
• ...: determined by assertion_info.n_args which has the total number of arguments passed to the assertion macro
• Where clause
  • open(path, 0): assertion_info.binary_diagnostics.left_expression
  • -1: assertion_info.binary_diagnostics.left_stringification
  • Same for the right side (omitted in this case because 0 => 0 isn't useful)
• Extra diagnostics
  • errno: assertion_info.extra_diagnostics[0].expression
  • 2 "No such file or directory": assertion_info.extra_diagnostics[0].stringification
  • ... etc.
• Stack trace
  • assertion_info.get_stacktrace(), or assertion_info.get_raw_trace() to get the trace without resolving it

Helpers:

assertion_info.header():

Debug Assertion failed at demo.cpp:194: void foo::baz(): Internal error with foobars
    debug_assert(open(path, 0) >= 0, ...);
    Where:
        open(path, 0) => -1
    Extra diagnostics:
        errno =>  2 "No such file or directory"
        path  => "/home/foobar/baz"

assertion_info.tagline():

Debug Assertion failed at demo.cpp:194: void foo::baz(): Internal error with foobars

assertion_info.location():

[!NOTE] Path processing will be performed according to the path mode

demo.cpp:194

assertion_info.statement():

    debug_assert(open(path, 0) >= 0, ...);

assertion_info.print_binary_diagnostics():

    Where:
        open(path, 0) => -1

assertion_info.print_extra_diagnostics():

    Extra diagnostics:
        errno =>  2 "No such file or directory"
        path  => "/home/foobar/baz"

assertion_info.print_stacktrace():

Stack trace:
#1 demo.cpp:194 foo::baz()
#2 demo.cpp:172 void foo::bar<int>(std::pair<int, int>)
#3 demo.cpp:396 main

Stringification of Custom Objects

Libassert provides a customization point for user-defined types:

template<> struct libassert::stringifier<MyObject> {
    std::string stringify(const MyObject& type) {
        return ...;
    }
};

By default any container-like user-defined types will be automatically stringifiable.

Additionally, LIBASSERT_USE_FMT can be used to allow libassert to use fmt::formatters.

Lastly, any types with an ostream operator<< overload can be stringified.

Custom Failure Handlers

namespace libassert {
    void set_failure_handler(void (*handler)(const assertion_info&));
}

• set_failure_handler: Sets the assertion handler for the program.

An example assertion handler similar to the default handler:

void libassert_default_failure_handler(const assertion_info& info) {
    libassert::enable_virtual_terminal_processing_if_needed(); // for terminal colors on windows
    std::string message = info.to_string(
        libassert::terminal_width(libassert::stderr_fileno),
        libassert::isatty(libassert::stderr_fileno)
            ? libassert::get_color_scheme()
            : libassert::color_scheme::blank
    );
    std::cerr << message << std::endl;
    switch(info.type) {
        case libassert::assert_type::assertion:
        case libassert::assert_type::debug_assertion:
        case libassert::assert_type::assumption:
        case libassert::assert_type::panic:
        case libassert::assert_type::unreachable:
            (void)fflush(stderr);
            std::abort();
            // Breaking here as debug CRT allows aborts to be ignored, if someone wants to make a
            // debug build of this library
            break;
        default:
            std::cerr << "Critical error: Unknown libassert::assert_type" << std::endl;
            std::abort(1);
    }
}

By default libassert aborts from all assertion types. However, it may be desirable to throw an exception from some or all assertion types instead of aborting.

[!IMPORTANT] Failure handlers must not return for assert_type::panic and assert_type::unreachable.

Breakpoints

Libassert supports programatic breakpoints on assertion failure to make assertions more debugger-friendly by breaking on the assertion line as opposed to several layers deep in a callstack:

This functionality is currently opt-in and it can be enabled by defining LIBASSERT_BREAK_ON_FAIL. This is best done as a compiler flag: -DLIBASSERT_BREAK_ON_FAIL or /DLIBASSERT_BREAK_ON_FAIL.

Internally the library checks for the presense of a debugger before executing an instruction to breakpoint the debugger. By default the check is only performed once on the first assertion failure. In some scenarios it may be desirable to configure this check to always be performed, e.g. if you're using a custom assertion handler that throws an exception instead of aborting and you may be able to recover from an assertion failure allowing additional failures later and you only attach a debugger part-way through the run of your program. You can use libassert::set_debugger_check_mode to control how this check is performed:

namespace libassert {
    enum class debugger_check_mode {
        check_once,
        check_every_time,
    };
    void set_debugger_check_mode(debugger_check_mode mode) noexcept;
}

The library also exposes its internal utilities for setting breakpoints and checking if the program is being debugged:

namespace libassert {
    bool is_debugger_present() noexcept;
}
#define LIBASSERT_BREAKPOINT() <...internals...>
#define LIBASSERT_BREAKPOINT_IF_DEBUGGING() <...internals...>

This API mimics the API of P2514, which has been accepted to C++26.

A note about constexpr: For clang and msvc libassert can use compiler intrinsics, however, for gcc inline assembly is required. Inline assembly isn't allowed in constexpr functions pre-C++20, however, gcc supports it with a warning after gcc 10 and the library can surpress that warning for gcc 12.

Other Configurations

Defines:

• LIBASSERT_USE_MAGIC_ENUM: Use magic enum for stringifying enum values
• LIBASSERT_DECOMPOSE_BINARY_LOGICAL: Decompose && and ||
• LIBASSERT_SAFE_COMPARISONS: Enable safe signed-unsigned comparisons for decomposed expressions
• LIBASSERT_PREFIX_ASSERTIONS: Prefixes all assertion macros with LIBASSERT_
• LIBASSERT_USE_FMT: Enables libfmt integration
• LIBASSERT_NO_STRINGIFY_SMART_POINTER_OBJECTS: Disables stringification of smart pointer contents

CMake:

• LIBASSERT_USE_EXTERNAL_CPPTRACE: Use an externam cpptrace instead of aquiring the library with FetchContent
• LIBASSERT_USE_EXTERNAL_MAGIC_ENUM: Use an externam magic enum instead of aquiring the library with FetchContent

Integration with Test Libraries

[!NOTE] Because of MSVC's non-conformant preprocessor there is no easy way to provide assertion wrappers. In order to use test library integrations /Zc:preprocessor is required.

Catch2

Libassert provides a catch2 integration in libassert/assert-catch2.hpp:

#include <libassert/assert-catch2.hpp>

TEST_CASE("1 + 1 is 2") {
    ASSERT(1 + 1 == 3);
}

Currently the only macro provided is ASSERT, which will perform a REQUIRE internally.

Note: Before v3.6.0 ansi color codes interfere with Catch2's line wrapping so color is disabled on older versions.

GoogleTest

Libassert provides a gtest integration in libassert/assert-gtest.hpp:

#include <libassert/assert-gtest.hpp>

TEST(Addition, Arithmetic) {
    ASSERT(1 + 1 == 3);
}

Currently libassert provides ASSERT and EXPECT macros for gtest.

This isn't as pretty as I would like, however, it gets the job done.

Usage

This library targets >=C++17 and supports all major compilers and all major platforms (linux, macos, windows, and mingw).

Note: The library does rely on some compiler extensions and compiler specific features so it is not compatible with -pedantic.

CMake FetchContent

With CMake FetchContent:

include(FetchContent)
FetchContent_Declare(
  libassert
  GIT_REPOSITORY https://github.com/jeremy-rifkin/libassert.git
  GIT_TAG        v2.1.2 # <HASH or TAG>
)
FetchContent_MakeAvailable(libassert)
target_link_libraries(your_target libassert::assert)

Note: On windows and macos some extra work is recommended, see Platform Logistics below.

Be sure to configure with -DCMAKE_BUILD_TYPE=Debug or -DDCMAKE_BUILD_TYPE=RelWithDebInfo for symbols and line information.

System-Wide Installation

git clone https://github.com/jeremy-rifkin/libassert.git
git checkout v2.1.2
mkdir libassert/build
cd libassert/build
cmake .. -DCMAKE_BUILD_TYPE=Release
make -j
sudo make install

Using through cmake:

find_package(libassert REQUIRED)
target_link_libraries(<your target> libassert::assert)

Be sure to configure with -DCMAKE_BUILD_TYPE=Debug or -DDCMAKE_BUILD_TYPE=RelWithDebInfo for symbols and line information.

Or compile with -lassert:

g++ main.cpp -o main -g -Wall -lassert
./main

If you get an error along the lines of

error while loading shared libraries: libassert.so: cannot open shared object file: No such file or directory

You may have to run sudo /sbin/ldconfig to create any necessary links and update caches so the system can find libcpptrace.so (I had to do this on Ubuntu). Only when installing system-wide. Usually your package manger does this for you when installing new libraries.

git clone https://github.com/jeremy-rifkin/libassert.git
git checkout v2.1.2
mkdir libassert/build
cd libassert/build
cmake .. -DCMAKE_BUILD_TYPE=Release
msbuild libassert.sln
msbuild INSTALL.vcxproj

Note: You'll need to run as an administrator in a developer powershell, or use vcvarsall.bat distributed with visual studio to get the correct environment variables set.

Local User Installation

To install just for the local user (or any custom prefix):

git clone https://github.com/jeremy-rifkin/libassert.git
git checkout v2.1.2
mkdir libassert/build
cd libassert/build
cmake .. -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=$HOME/wherever
make -j
sudo make install

Using through cmake:

find_package(libassert REQUIRED PATHS $ENV{HOME}/wherever)
target_link_libraries(<your target> libassert::assert)

Using manually:

g++ main.cpp -o main -g -Wall -I$HOME/wherever/include -L$HOME/wherever/lib -lassert

Use Without CMake

To use the library without cmake first follow the installation instructions at System-Wide Installation, Local User Installation, or Package Managers.

Use the following arguments to compile with libassert:

Compiler	Platform	Dependencies
gcc, clang, intel, etc.	Linux/macos/unix	-libassert -I[path] [cpptrace args]
mingw	Windows	-libassert -I[path] [cpptrace args]
msvc	Windows	assert.lib /I[path] [cpptrace args]
clang	Windows	-libassert -I[path] [cpptrace args]

For the [path] placeholder in -I[path] and /I[path], specify the path to the include folder containing libassert/assert.hpp.

If you are linking statically, you will additionally need to specify -DLIBASSERT_STATIC_DEFINE.

For the [cpptrace args] placeholder refer to the cpptrace documentation.

Package Managers

Conan

Libassert is available through conan at https://conan.io/center/recipes/libassert.

[requires]
libassert/2.1.2
[generators]
CMakeDeps
CMakeToolchain
[layout]
cmake_layout

# ...
find_package(libassert REQUIRED)
# ...
target_link_libraries(YOUR_TARGET libassert::assert)

Vcpkg

vcpkg install libassert

find_package(libassert CONFIG REQUIRED)
target_link_libraries(YOUR_TARGET PRIVATE libassert::assert)

Platform Logistics

Windows and macos require a little extra work to get everything in the right place

Copying the library .dll on windows:

# Copy the assert.dll on windows to the same directory as the executable for your_target.
# Not required if static linking.
if(WIN32)
  add_custom_command(
    TARGET your_target POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E copy_if_different
    $<TARGET_FILE:libassert::assert>
    $<TARGET_FILE_DIR:your_target>
  )
endif()

On macOS it's recommended to generate a dSYM file containing debug information for your program:

In xcode cmake this can be done with

set_target_properties(your_target PROPERTIES XCODE_ATTRIBUTE_DEBUG_INFORMATION_FORMAT "dwarf-with-dsym")

And outside xcode this can be done with dsymutil yourbinary:

# Create a .dSYM file on macos. Currently required, but hopefully not for long
if(APPLE)
  add_custom_command(
    TARGET your_target
    POST_BUILD
    COMMAND dsymutil $<TARGET_FILE:your_target>
  )
endif()

Replacing <cassert>

This library is not a drop-in replacement for <cassert>. -DLIBASSERT_LOWERCASE can be used to create lowercase aliases for the assertion macros but be aware that libassert's ASSERT is still checked in release. To replace <cassert> use with libassert, replace assert with DEBUG_ASSERT or create an alias along the following lines:

#define assert(...) DEBUG_ASSERT(__VA_ARGS__)

One thing to be aware: Overriding cassert's assert is technically not allowed by the standard, but this should not be an issue for any sane compiler.

FAQ

Does it have spell-check?

No, not yet.

Cool projects using libassert

• Morwenn's cpp-sort

Comparison With Other Languages

Even with constructs like assert_eq, assertion diagnostics are often lacking. For example, in rust the left and right values are displayed but not the expressions themselves:

fn main() {
    let count = 4;
    assert_eq!(count, 2);
}

thread 'main' panicked at 'assertion failed: `(left == right)`
  left: `4`,
 right: `2`', /app/example.rs:3:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

This is not as helpful as it could be.

Functionality other languages / their standard libraries provide:

	C/C++	Rust	C#	Java	Python	JavaScript	Libassert
Expression string	✔️	❌	❌	❌	❌	❌	✔️
Location	✔️	✔️	✔️	✔️	✔️	✔️	✔️
Stack trace	❌	✔️	✔️	✔️	✔️	✔️	✔️
Assertion message	❌**	✔️	✔️	✔️	✔️	✔️	✔️
Extra diagnostics	❌	❌*	❌*	❌	❌*	❌*	✔️
Binary specializations	❌	✔️	❌	❌	❌	✔️	✔️
Automatic expression decomposition	❌	❌	❌	❌	❌	❌	✔️
Sub-expression strings	❌	❌	❌	❌	❌	❌	✔️

*: Possible through string formatting but that is sub-ideal. **: assert(expression && "message") is commonly used but this is sub-ideal and only allows string literal messages.

Extras:

	C/C++	Rust	C#	Java	Python	JavaScript	Libassert
Syntax highlighting	❌	❌	❌	❌	🟡	❌	✔️
Literal formatting consistency	❌	❌	❌	❌	❌	❌	✔️
Expression strings and expression values everywhere	❌	❌	❌	❌	❌	❌	✔️
Return values from the assert to allow asserts to be integrated into expressions inline	❌	❌	❌	❌	❌	❌	✔️