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    <p>First, your code is neither valid C nor valid C++.</p> <p>Perhaps you mean:</p> <pre><code> char str* = new char[512]; delete[] str; </code></pre> <p>which is valid C++ (not C, because <code>new</code> and <code>delete</code> are C++ keywords, not C ones) and works on Linux as it does on Windows or any standard C++ implementation.</p> <p>Then, the <code>str</code> is allocated in the <a href="http://en.wikipedia.org/wiki/Memory_management" rel="nofollow">heap</a> (and the same program is allocating in the heap both on Windows and on Linux).</p> <p>There is no need for <a href="http://man7.org/linux/man-pages/man3/posix_memalign.3.html" rel="nofollow">posix_memalign(3)</a> (please look at the man page I just linked) in your case.</p> <p>You could want to use <code>posix_memalign</code> if for some particular reason you wanted the pointer to be aligned, e.g. be a multiple of 1024. </p> <p><sup>This example is silly on purpose, because it asks an alignment of 1024 bytes for a memory zone of 512 bytes.</sup></p> <p>Then please have</p> <pre><code> #define _GNU_SOURCE #include &lt;new&gt; #include &lt;stdlib.h&gt; </code></pre> <p>and later in the same C++ source file:</p> <pre><code> char* str = NULL; void* ad = NULL; if (posix_memalign(&amp;ad, 1024, 512)) { perror("posix_memalign failed"); exit (EXIT_FAILURE); } str = new(ad) char[512]; </code></pre> <p>but you should have some particular reason to want an aligned pointer (here, a multiple of 1Kbyte). Usually you don't want pointer to be aligned more than the default. (You may require a large alignment, e.g. if doing arithmetic on <code>(intptr_t)</code> casts of your pointers; but this is very unusual). Notice the <a href="http://en.wikipedia.org/wiki/Placement_new" rel="nofollow">placement new</a> (provided by the <code>&lt;new&gt;</code> standard header).</p> <p>I recommend reading <a href="http://advancedlinuxprogramming.com/" rel="nofollow">Advanced Linux Programming</a> (which is more focused on C than on C++). And always compile on Linux with all warnings requested by the compiler and debugging info (e.g. <code>g++ -Wall -g</code>). Learn to use the <code>gdb</code> debugger and the <code>valgrind</code> memory leak detector. Once your program has no bugs, consider asking the compiler to optimize its produced object code with <code>g++ -Wall -O2</code> instead of <code>g++ -Wall -g</code>.</p> <p>actually, the real <a href="http://en.wikipedia.org/wiki/Syscall" rel="nofollow">syscalls</a> done by your application to the <a href="http://en.wikipedia.org/wiki/Linux_kernel" rel="nofollow">Linux kernel</a> (whose list is on <a href="http://man7.org/linux/man-pages/man2/syscalls.2.html" rel="nofollow">syscalls(2)</a>) for memory management are <a href="http://man7.org/linux/man-pages/man2/mmap.2.html" rel="nofollow">mmap(2)</a> and <code>munmap(2)</code> (and perhaps <code>sbrk(2)</code> which is nearly obsolete). You should use the <code>strace</code> command to find out the many syscalls done by a process.</p>
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    1. COAhh, I am trying to build a scanner for my compiler(a homework in fact ^^). My professor said we should use posix_memalign for our buffer. I thought that is because it is linux standard.
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    2. CODo as you teacher requires. `posix_memalign` is not Linux specific, it is defined in the POSIX standard. But there are few good reasons to require a largely aligned buffer....
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