{"id":14006,"date":"2022-10-06T05:31:10","date_gmt":"2022-10-06T00:01:10","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-in-c-program-why-free-memory-of-string-which-copy-from-strcpy-in-osx-is-not-woking-duplicate\/"},"modified":"2022-10-06T05:31:10","modified_gmt":"2022-10-06T00:01:10","slug":"solved-in-c-program-why-free-memory-of-string-which-copy-from-strcpy-in-osx-is-not-woking-duplicate","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-in-c-program-why-free-memory-of-string-which-copy-from-strcpy-in-osx-is-not-woking-duplicate\/","title":{"rendered":"[Solved] In c program, why free memory of string (which copy from strcpy) in osx is not woking? [duplicate]"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-43861633\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"43861633\" data-parentid=\"43861554\" data-score=\"2\" data-position-on-page=\"1\" data-highest-scored=\"1\" data-question-has-accepted-highest-score=\"1\" itemprop=\"acceptedAnswer\" itemscope itemtype=\"https:\/\/schema.org\/Answer\">\n<div class=\"post-layout\">\n<div class=\"votecell post-layout--left\"><\/div>\n<div class=\"answercell post-layout--right\">\n<div class=\"s-prose js-post-body\" itemprop=\"text\">\n<p>Your problem is your placement of <code>free(copy)<\/code>, move it <strong>after<\/strong> you make use of <code>copy<\/code>, otherwise you are attempting to read from a variable that has already been <code>freed<\/code> (an uninitialized value &#8211; invoking <strong>Undefined Behavior<\/strong>), (as @Pras correctly notes you <code>free (copy)<\/code>, not <code>free (origin)<\/code>, e.g.<\/p>\n<pre><code>#include &lt;string.h&gt;\n#include &lt;stdlib.h&gt;\n#include &lt;stdio.h&gt;\n\nint main(){\n    char *copy;\n    char *origin = \"tutorialspoint\";\n    copy = malloc (strlen (origin) + 1);\n    strcpy(copy, origin);\n\n    printf(\"string = %s,  Address = %p\\n\", copy, (void *)copy);\n    printf(\"origin = %s,  Address = %p\\n\", origin, (void *)origin);\n    free(copy);  \/* works find here *\/\n    return(0);\n}\n<\/code><\/pre>\n<p><strong>note:<\/strong> use of <code>%p<\/code> for the pointer address.<\/p>\n<p>You should also <strong>validate ALL memory allocations<\/strong>, e.g.<\/p>\n<pre><code>    if (!(copy = malloc (strlen (origin) + 1))) {\n        fprintf (stderr, \"error: virtual memory exhausted.\\n\");\n        return 1;\n    }\n<\/code><\/pre>\n<p><strong>Example Use\/Output<\/strong><\/p>\n<pre><code>$ .\/bin\/origin\nstring = tutorialspoint,  Address = 0xbe3010\norigin = tutorialspoint,  Address = 0x400710\n<\/code><\/pre>\n<hr>\n<p><strong>copy is freed<\/strong><\/p>\n<p>Continuing from your comment, <code>copy<\/code> is in fact freed. How can you tell? You run you code through a memory\/error checking program like <code>valgrind<\/code>, e.g.<\/p>\n<pre><code>$ valgrind .\/bin\/origin\n==10564== Memcheck, a memory error detector\n==10564== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.\n==10564== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info\n==10564== Command: .\/bin\/origin\n==10564==\nstring = tutorialspoint,  Address = 0x51d8040\norigin = tutorialspoint,  Address = 0x400710\n==10564==\n==10564== HEAP SUMMARY:\n==10564==     in use at exit: 0 bytes in 0 blocks\n==10564==   total heap usage: 1 allocs, 1 frees, 15 bytes allocated\n==10564==\n==10564== All heap blocks were freed -- no leaks are possible\n==10564==\n==10564== For counts of detected and suppressed errors, rerun with: -v\n==10564== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)\n<\/code><\/pre>\n<p>As you can see, all memory allocated had in fact been freed and &#8212; no leaks are possible and there were 0 errors from 0 contexts.<\/p>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\">6<\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved In c program, why free memory of string (which copy from strcpy) in osx is not woking? [duplicate] <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] Your problem is your placement of free(copy), move it after you make use of copy, otherwise you are attempting to read from a variable that has already been freed (an uninitialized value &#8211; invoking Undefined Behavior), (as @Pras correctly notes you free (copy), not free (origin), e.g. #include &lt;string.h&gt; #include &lt;stdlib.h&gt; #include &lt;stdio.h&gt; int &#8230; <a title=\"[Solved] In c program, why free memory of string (which copy from strcpy) in osx is not woking? [duplicate]\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-in-c-program-why-free-memory-of-string-which-copy-from-strcpy-in-osx-is-not-woking-duplicate\/\" aria-label=\"More on [Solved] In c program, why free memory of string (which copy from strcpy) in osx is not woking? [duplicate]\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[324,876,535],"class_list":["post-14006","post","type-post","status-publish","format-standard","hentry","category-solved","tag-c","tag-macos","tag-memory"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] In c program, why free memory of string (which copy from strcpy) in osx is not woking? 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