SMART_ASSERT

A lightweight, multi-expression assertion macro for C and C++, with optional debug-only usage.

Why use this?

A simple and powerful assertion macro that improves debug visibility with minimal code by allowing multiple conditions in a single statement — while keeping production builds fast and clean.

Standard assert() is a "fail-fast" gate: it stops at the first failure. If your logic requires three pointers and a state flag to be valid, standard assert only tells you about the first one that failed.

SMART_ASSERT() macro evaluates every condition passed to it before halting. This provides a complete "State Snapshot" of the failure, allowing you to see exactly which invariants were violated in a single crash report.

Features

• Supports multiple conditions in one assert call
• Prints exactly which condition(s) failed
• Includes file, line, and function name
• Works in C99 and C++20 (or newer)
• Fully header-only, zero dependencies
• Compatible with both C and C++
• Offers optional debug-only behavior via DEBUG_SMART_ASSERT(...)

Usage

Include the header:

#include "smart_assert.h"

To enable debug-only assertions, define DEBUG_MODE before including the header:

#define DEBUG_MODE
#include "smart_assert.h"

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Macro Overview

SMART_ASSERT(...)

Evaluates one or more conditions and prints a detailed failure message for each failed condition.
Always enabled, regardless of build configuration.

SMART_ASSERT(x > 0, y == 5, is_valid());

DEBUG_SMART_ASSERT(...)

A wrapper macro for SMART_ASSERT(...) that is:

• Enabled only when DEBUG_MODE is defined
• Disabled otherwise — but still evaluates the expressions (side effects are preserved)

Example:

DEBUG_SMART_ASSERT(x++ < 10); // x++ still happens in release

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Example

#define DEBUG_MODE
#include "smart_assert.h"

int main(void) {
    int a = 1, b = 2, c = 0;

    // This will print failures for b == 3 and c++ == 1
    DEBUG_SMART_ASSERT(a == 1, b == 3, c++ == 1);

    return 0;
}

Output:

main.c:8: main: SMART_ASSERT(): Condition #2: `b == 3` failed.
main.c:8: main: SMART_ASSERT(): Condition #3: `c++ == 1` failed.

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Behavior When DEBUG_MODE Is Not Defined

• DEBUG_SMART_ASSERT(...) becomes:

  (void)(__VA_ARGS__); // All expressions are still evaluated

• No assertions, no messages, no aborts
• Useful for maintaining debug logic without performance cost in production

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!Note

MASSERT correctly handles nested parentheses and braces but may be confused by commas inside string literals (e.g., MASSERT(s == "a,b")) as it does not implement a full C lexer.

Integration Steps

1. Copy smart_assert.h to your project (e.g. include/ folder)
2. Optionally define DEBUG_MODE in debug builds
3. Use SMART_ASSERT(...) for always-on checks
4. Use DEBUG_SMART_ASSERT(...) for debug-only assertions

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Requirements

Feature	Requirement
C Standard	C99 or newer (_Bool, _Static_assert, variadic macros)
C++ Standard	C++20 or newer (__VA_OPT__)
Compiler	GCC, Clang, or compatible

License

MIT License © 2024 Georgios Evangelinos

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