projects / thirdparty / man-pages.git / blame
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1 | .\" Copyright (c) 2012 by Michael Kerrisk <mtk.manpages@gmail.com> |
| 2 | .\" | |
| 5fbde956 | 3 | .\" SPDX-License-Identifier: Linux-man-pages-copyleft |
| 6978778c | 4 | .\" |
| 1d767b55 | 5 | .TH MALLOC_USABLE_SIZE 3 2021-03-22 "GNU" "Linux Programmer's Manual" |
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6 | .SH NAME |
| 7 | malloc_usable_size \- obtain size of block of memory allocated from heap | |
| ce9ba99d AC |
8 | .SH LIBRARY |
| 9 | Standard C library | |
| 10 | .RI ( libc ", " -lc ) | |
| 6978778c | 11 | .SH SYNOPSIS |
| c7db92b9 | 12 | .nf |
| 6978778c | 13 | .B #include <malloc.h> |
| dbfe9c70 | 14 | .PP |
| 27398f1b | 15 | .BI "size_t malloc_usable_size(void *" ptr ); |
| c7db92b9 | 16 | .fi |
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17 | .SH DESCRIPTION |
| 18 | The | |
| 19 | .BR malloc_usable_size () | |
| 20 | function returns the number of usable bytes in the block pointed to by | |
| 21 | .IR ptr , | |
| 22 | a pointer to a block of memory allocated by | |
| 23 | .BR malloc (3) | |
| 24 | or a related function. | |
| 25 | .SH RETURN VALUE | |
| 26 | .BR malloc_usable_size () | |
| 27 | returns the number of usable bytes in | |
| 28 | the block of allocated memory pointed to by | |
| 29 | .IR ptr . | |
| 30 | If | |
| 31 | .I ptr | |
| 32 | is NULL, 0 is returned. | |
| 4b5ef086 | 33 | .SH ATTRIBUTES |
| bb374f15 PH |
34 | For an explanation of the terms used in this section, see |
| 35 | .BR attributes (7). | |
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36 | .ad l |
| 37 | .nh | |
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38 | .TS |
| 39 | allbox; | |
| c466875e | 40 | lbx lb lb |
| bb374f15 PH |
41 | l l l. |
| 42 | Interface Attribute Value | |
| 43 | T{ | |
| 4b5ef086 | 44 | .BR malloc_usable_size () |
| bb374f15 PH |
45 | T} Thread safety MT-Safe |
| 46 | .TE | |
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47 | .hy |
| 48 | .ad | |
| 49 | .sp 1 | |
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50 | .SH CONFORMING TO |
| 51 | This function is a GNU extension. | |
| 52 | .SH NOTES | |
| 53 | The value returned by | |
| 54 | .BR malloc_usable_size () | |
| 55 | may be greater than the requested size of the allocation because | |
| 56 | of alignment and minimum size constraints. | |
| 57 | Although the excess bytes can be overwritten by the application | |
| 58 | without ill effects, | |
| 59 | this is not good programming practice: | |
| 60 | the number of excess bytes in an allocation depends on | |
| 61 | the underlying implementation. | |
| 847e0d88 | 62 | .PP |
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63 | The main use of this function is for debugging and introspection. |
| 64 | .SH SEE ALSO | |
| 65 | .BR malloc (3) |