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diff --git a/devdocs/c/types%2Fptrdiff_t.html b/devdocs/c/types%2Fptrdiff_t.html new file mode 100644 index 00000000..a576a926 --- /dev/null +++ b/devdocs/c/types%2Fptrdiff_t.html @@ -0,0 +1,56 @@ + <h1 id="firstHeading" class="firstHeading">ptrdiff_t</h1> <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code><stddef.h></code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl"> <td class="t-dcl-nopad"> <pre data-language="c">typedef /*implementation-defined*/ ptrdiff_t;</pre> +</td> <td class="t-dcl-nopad"> </td> <td class="t-dcl-nopad"> </td> </tr> </table> <p><code>ptrdiff_t</code> is the signed integer type of the result of <a href="../language/operator_arithmetic#Pointer_arithmetic" title="c/language/operator arithmetic">subtracting two pointers</a>.</p> +<table class="t-rev-begin"> <tr class="t-rev t-since-c99 t-until-c23"> +<td> <p>The bit width of <code>ptrdiff_t</code> is not less than 17.</p> +</td> <td> +<span class="t-mark-rev t-since-c99">(since C99)</span><br><span class="t-mark-rev t-until-c23">(until C23)</span> +</td> +</tr> <tr class="t-rev t-since-c23"> +<td> <p>The bit width of <code>ptrdiff_t</code> is not less than 16.</p> +</td> <td><span class="t-mark-rev t-since-c23">(since C23)</span></td> +</tr> </table> <h3 id="Notes"> Notes</h3> <p><code>ptrdiff_t</code> is used for pointer arithmetic and array indexing, if negative values are possible. Programs that use other types, such as <code>int</code>, may fail on, e.g. 64-bit systems when the index exceeds <code><a href="limits" title="c/types/limits">INT_MAX</a></code> or if it relies on 32-bit modular arithmetic.</p> +<p>Only pointers to elements of the same array (including the pointer one past the end of the array) may be subtracted from each other.</p> +<p>If an array is so large (greater than <code><a href="limits" title="c/types/limits">PTRDIFF_MAX</a></code> elements, but equal to or less than <code><a href="limits" title="c/types/limits">SIZE_MAX</a></code> bytes), that the difference between two pointers may not be representable as <code>ptrdiff_t</code>, the result of subtracting two such pointers is undefined.</p> +<p>For char arrays shorter than <code><a href="limits" title="c/types/limits">PTRDIFF_MAX</a></code>, <code>ptrdiff_t</code> acts as the signed counterpart of <code><a href="size_t" title="c/types/size t">size_t</a></code>: it can store the size of the array of any type and is, on most platforms, synonymous with <code>intptr_t</code>).</p> +<h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#include <stddef.h> +#include <stdint.h> +#include <stdio.h> + +int main(void) +{ + const size_t N = 100; + int numbers[N]; + + printf("PTRDIFF_MAX = %ld\n", PTRDIFF_MAX); + int *p1 = &numbers[18], *p2 = &numbers[23]; + ptrdiff_t diff = p2 - p1; + printf("p2-p1 = %td\n", diff); +}</pre></div> <p>Possible output:</p> +<div class="text source-text"><pre data-language="c">PTRDIFF_MAX = 9223372036854775807 +p2-p1 = 5</pre></div> </div> <h3 id="References"> References</h3> <ul> +<li> C17 standard (ISO/IEC 9899:2018): </li> +<ul> +<li> 7.19 Common definitions <stddef.h> (p: 211) </li> +<li> 7.20.3 Limits of other integer types (p: 215) </li> +</ul> +<li> C11 standard (ISO/IEC 9899:2011): </li> +<ul> +<li> 7.19 Common definitions <stddef.h> (p: 288) </li> +<li> 7.20.3 Limits of other integer types (p: 293) </li> +</ul> +<li> C99 standard (ISO/IEC 9899:1999): </li> +<ul> +<li> 7.17 Common definitions <stddef.h> (p: 253) </li> +<li> 7.18.3 Limits of other integer types (p: 258) </li> +</ul> +<li> C89/C90 standard (ISO/IEC 9899:1990): </li> +<ul><li> 4.1.6 Common definitions <stddef.h> </li></ul> +</ul> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="size_t" title="c/types/size t"> <span class="t-lines"><span>size_t</span></span></a></div> </td> <td> unsigned integer type returned by the <a href="../language/sizeof" title="c/language/sizeof"><code>sizeof</code></a> operator <br> <span class="t-mark">(typedef)</span> </td> +</tr> <tr class="t-dsc"> <td> <div><a href="offsetof" title="c/types/offsetof"> <span class="t-lines"><span>offsetof</span></span></a></div> </td> <td> byte offset from the beginning of a struct type to specified member <br> <span class="t-mark">(function macro)</span> </td> +</tr> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/types/ptrdiff_t" title="cpp/types/ptrdiff t">C++ documentation</a></span> for <code>ptrdiff_t</code> </td> +</tr> </table> <div class="_attribution"> + <p class="_attribution-p"> + © cppreference.com<br>Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.<br> + <a href="https://en.cppreference.com/w/c/types/ptrdiff_t" class="_attribution-link">https://en.cppreference.com/w/c/types/ptrdiff_t</a> + </p> +</div> |