Implementation:ClickHouse ClickHouse Defines

Knowledge Sources	ClickHouse
Domains	Build_System, Portability
Last Updated	2026-02-08 00:00 GMT

Overview

Core compiler macros and definitions used throughout ClickHouse for portability and optimization.

Description

Defines platform checks, compiler hints (likely/unlikely), inlining directives, assertion macros (chassert), and Thread Safety Analysis annotations.

Usage

Use for writing portable code, adding compiler hints, implementing assertions, or annotating code for TSA.

Code Reference

Source Location

• Repository: ClickHouse
• File: base/base/defines.h
• Lines: 1-91

Signature

// Branch prediction hints
#define likely(x)   (__builtin_expect(!!(x), 1))
#define unlikely(x) (__builtin_expect(!!(x), 0))

// Inlining control
#define ALWAYS_INLINE __attribute__((__always_inline__))
#define NO_INLINE __attribute__((__noinline__))

// Assertions
#define chassert(x) /* ... */
#define UNREACHABLE() /* ... */

// Thread Safety Analysis
#define TSA_GUARDED_BY(...)
#define TSA_REQUIRES(...)
#define TSA_NO_THREAD_SAFETY_ANALYSIS

Import

#include <base/defines.h>

Usage Examples

#include <base/defines.h>

// Branch hints
if (likely(common_case)) {
    // Compiler optimizes for this path
}

if (unlikely(error_condition)) {
    // Rare path
}

// Force inlining
ALWAYS_INLINE void hot_function() { }

// Assertions
chassert(ptr != nullptr);
chassert(size > 0, "Size must be positive");

// Thread safety annotations
int counter TSA_GUARDED_BY(mutex);

Related Pages

• Principle:ClickHouse_ClickHouse_Core_Compiler_Macros