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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head> <meta name="generator" content= "HTML Tidy for Linux/x86 (vers 1 September 2005), see www.w3.org"> <title>Standard C Memory</title> <link href="../cppreference.css" rel="stylesheet" type="text/css"></head><body><table> <tr> <td> <div class="body-content"> <div class="header-box"> <a href="../index.html">cppreference.com</a> > <a href= "index.html">Standard C Memory</a> </div> <div class="name-format"> calloc </div> <div class="syntax-name-format"> Syntax: </div> <pre class="syntax-box"> #include <stdlib.h> void* calloc( size_t num, size_t size );</pre> <p>The calloc() function returns a pointer to space for an array of <em>num</em> objects, each of size <em>size</em>. The newly allocated memory is initialized to zero.</p> <p>calloc() returns <strong>NULL</strong> if there is an error.</p> <div class="related-name-format"> Related topics: </div> <div class="related-content"> <a href="free.html">free</a><br> <a href="malloc.html">malloc</a><br> <a href="realloc.html">realloc</a> </div> </div> </td> </tr> </table></body></html><hr> <div class="name-format"> free </div> <div class="syntax-name-format"> Syntax: </div> <pre class="syntax-box"> #include <stdlib.h> void free( void* ptr );</pre> <p>The free() function deallocates the space pointed to by <em>ptr</em>, freeing it up for future use. <em>ptr</em> must have been used in a previous call to <a href="malloc.html">malloc</a>(), <a href="calloc.html">calloc</a>(), or <a href= "realloc.html">realloc</a>(). An example:</p> <pre class="example-code"> typedef struct data_type { int age; char name[20]; } data; data *willy; willy = (data*) malloc( sizeof(*willy) ); ... free( willy ); </pre> <div class="related-name-format"> Related topics: </div> <div class="related-content"> <a href="calloc.html">calloc</a><br> (C/C++ Keywords) <a href="../keywords/delete.html">delete</a><br> <a href="malloc.html">malloc</a><br> (C/C++ Keywords) <a href="../keywords/new.html">new</a><br> <a href="realloc.html">realloc</a> </div> </div> </td> </tr> </table></body></html><hr> <div class="name-format"> malloc </div> <div class="syntax-name-format"> Syntax: </div> <pre class="syntax-box"> #include <stdlib.h> void *malloc( size_t size );</pre> <p>The function malloc() returns a pointer to a chunk of memory of size <em>size</em>, or <strong>NULL</strong> if there is an error. The memory pointed to will be on the heap, not the stack, so make sure to free it when you are done with it. An example:</p> <pre class="example-code"> typedef struct data_type { int age; char name[20]; } data; data *bob; bob = (data*) malloc( sizeof(data) ); if( bob != <strong>NULL</strong> ) { bob->age = 22; strcpy( bob->name, "Robert" ); printf( "%s is %d years old\n", bob->name, bob->age ); } free( bob ); </pre> <div class="related-name-format"> Related topics: </div> <div class="related-content"> <a href="calloc.html">calloc</a><br> (C/C++ Keywords) <a href="../keywords/delete.html">delete</a><br> <a href="free.html">free</a><br> (C/C++ Keywords) <a href="../keywords/new.html">new</a><br> <a href="realloc.html">realloc</a> </div> </div> </td> </tr> </table></body></html><hr> <div class="name-format"> realloc </div> <div class="syntax-name-format"> Syntax: </div> <pre class="syntax-box"> #include <stdlib.h> void *realloc( void *ptr, size_t size );</pre> <p>The realloc() function changes the size of the object pointed to by ptr to the given size. size can be any size, larger or smaller than the original. The return value is a pointer to the new space, or <strong>NULL</strong> if there is an error.</p> <div class="related-name-format"> Related topics: </div> <div class="related-content"> <a href="calloc.html">calloc</a><br> <a href="free.html">free</a><br> <a href="malloc.html">malloc</a> </div> </div> </td> </tr> </table></body></html><hr></body></html>⌨️ 快捷键说明
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