How Can I Retrieve Available System Memory in C Across Different Platforms?

Retrieving Available Memory in C /g

In scenarios where memory allocation must adapt to available system resources, there is a need to determine the amount of memory available to an application at runtime. This article explores methods for platform-independent retrieval of available memory on Windows, macOS, Linux, and AIX.

UNIX-Like Systems (Linux, macOS, AIX)

The sysconf function provides a standardized way to obtain system configuration parameters, including memory information. The code below uses sysconf to query the total physical memory:

#include <unistd.h>

unsigned long long getTotalSystemMemory()
{
    long pages = sysconf(_SC_PHYS_PAGES);
    long page_size = sysconf(_SC_PAGE_SIZE);
    return pages * page_size;
}

Windows

On Windows, the GlobalMemoryStatusEx function provides detailed information about memory usage, including total physical memory:

#include <windows.h>

unsigned long long getTotalSystemMemory()
{
    MEMORYSTATUSEX status;
    status.dwLength = sizeof(status);
    GlobalMemoryStatusEx(&status);
    return status.ullTotalPhys;
}

Usage

To use this information in your application, you can define a cross-platform function that returns the available memory:

#ifdef WIN32
unsigned long long getTotalSystemMemory()
{
    return GlobalMemoryStatusEx();
}
#else
unsigned long long getTotalSystemMemory()
{
    return sysconf(_SC_PHYS_PAGES) * sysconf(_SC_PAGE_SIZE);
}
#endif

Then, you can allocate buffers based on the available memory:

void allocateBuffers()
{
    unsigned long long availableMemory = getTotalSystemMemory();
    // Allocate buffers according to `availableMemory`
}

Note that the concept of virtual versus physical memory may vary between platforms and operating systems, so it is essential to use the correct functions for each target system.

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