Basic Definitions 
#include "co/def.h"

#Integer Type Aliases

typedef int8_t  int8;
typedef int16_t int16;
typedef int32_t int32;
typedef int64_t int64;
typedef uint8_t  uint8;
typedef uint16_t uint16;
typedef uint32_t uint32;
typedef uint64_t uint64;
  • Defined in the global namespace.

#Integer Extreme Value Constants

namespace co {

constexpr uint8  max_uint8  = (uint8)  ~((uint8) 0);
constexpr uint16 max_uint16 = (uint16) ~((uint16)0);
constexpr uint32 max_uint32 = (uint32) ~((uint32)0);
constexpr uint64 max_uint64 = (uint64) ~((uint64)0);
constexpr int8  max_int8  = (int8)  (max_uint8  >> 1);
constexpr int16 max_int16 = (int16) (max_uint16 >> 1);
constexpr int32 max_int32 = (int32) (max_uint32 >> 1);
constexpr int64 max_int64 = (int64) (max_uint64 >> 1);
constexpr int8  min_int8  = (int8)  ~max_int8;
constexpr int16 min_int16 = (int16) ~max_int16;
constexpr int32 min_int32 = (int32) ~max_int32;
constexpr int64 min_int64 = (int64) ~max_int64;

} // co
  • Defined in the co namespace; all are constexpr.

Example:

#include "co/def.h"
#include "co/print.h"

int main() {
    co::println("max_uint32 = ", co::max_uint32);
    co::println("max_int32  = ", co::max_int32);
    co::println("min_int32  = ", co::min_int32);
    return 0;
}

#Cache Line Size

Provides the compile-time constant co::cache_line_size, commonly used for memory alignment and avoiding false sharing. Values for each architecture are as follows:

Architecture co::cache_line_size
S390X 256
PowerPC64 128
ARM64 128
Others (x86, x64, etc.) 64
co::cache_line_size may be larger than the actual cache line size. When aligning or padding, it will occupy a small amount of extra memory, which usually has little impact.

Example:

// Allocate cache-line-aligned memory
co::alloc(n, co::cache_line_size);

#Macros

#Architecture

#if SIZE_MAX == UINT64_MAX
#define __arch64 1
#elif SIZE_MAX == UINT32_MAX
#define __arch32 1
#else
#error "platform not supported"
#endif
  • On 64-bit platforms, the __arch64 macro is defined with a value of 1;
  • On 32-bit platforms, the __arch32 macro is defined with a value of 1;

#Cache Line Alignment

#ifndef __cacheline_aligned
#define __cacheline_aligned alignas(co::cache_line_size)
#endif
  • The __cacheline_aligned macro aligns a variable or struct to a cache line.

Example:

struct __cacheline_aligned Foo {
    int x;
};

#Thread-Local Storage

#ifdef _MSC_VER
#ifndef __thread
#define __thread __declspec(thread)
#endif
#endif
  • __thread is used to define thread-local variables;
  • gcc/clang already have built-in __thread; on Windows (using MSVC), it is defined as __declspec(thread).

Example:

__thread int g_v;
__thread void* g_p;

#__unlikely

  • Hints to the compiler that a condition is more likely to be false.
  • In older versions it was named unlikey; to avoid conflict with C++20 [[unlikely]], it was changed to __unlikely.

Example:

fs::file f("xx.log", 'r');
if (__unlikely(!f)) co::println("open file failed");