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1 | .\" Copyright (c) 2012 by Michael Kerrisk <mtk.manpages@gmail.com> |
| 2 | .\" | |
| 93015253 | 3 | .\" %%%LICENSE_START(VERBATIM) |
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4 | .\" Permission is granted to make and distribute verbatim copies of this |
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| 6978778c | 24 | .\" |
| 4b8c67d9 | 25 | .TH MALLOC_USABLE_SIZE 3 2017-09-15 "GNU" "Linux Programmer's Manual" |
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26 | .SH NAME |
| 27 | malloc_usable_size \- obtain size of block of memory allocated from heap | |
| 28 | .SH SYNOPSIS | |
| 29 | .B #include <malloc.h> | |
| dbfe9c70 | 30 | .PP |
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31 | .BI "size_t malloc_usable_size (void *" ptr ); |
| 32 | .SH DESCRIPTION | |
| 33 | The | |
| 34 | .BR malloc_usable_size () | |
| 35 | function returns the number of usable bytes in the block pointed to by | |
| 36 | .IR ptr , | |
| 37 | a pointer to a block of memory allocated by | |
| 38 | .BR malloc (3) | |
| 39 | or a related function. | |
| 40 | .SH RETURN VALUE | |
| 41 | .BR malloc_usable_size () | |
| 42 | returns the number of usable bytes in | |
| 43 | the block of allocated memory pointed to by | |
| 44 | .IR ptr . | |
| 45 | If | |
| 46 | .I ptr | |
| 47 | is NULL, 0 is returned. | |
| 4b5ef086 | 48 | .SH ATTRIBUTES |
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49 | For an explanation of the terms used in this section, see |
| 50 | .BR attributes (7). | |
| 51 | .TS | |
| 52 | allbox; | |
| 53 | lbw20 lb lb | |
| 54 | l l l. | |
| 55 | Interface Attribute Value | |
| 56 | T{ | |
| 4b5ef086 | 57 | .BR malloc_usable_size () |
| bb374f15 PH |
58 | T} Thread safety MT-Safe |
| 59 | .TE | |
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60 | .SH CONFORMING TO |
| 61 | This function is a GNU extension. | |
| 62 | .SH NOTES | |
| 63 | The value returned by | |
| 64 | .BR malloc_usable_size () | |
| 65 | may be greater than the requested size of the allocation because | |
| 66 | of alignment and minimum size constraints. | |
| 67 | Although the excess bytes can be overwritten by the application | |
| 68 | without ill effects, | |
| 69 | this is not good programming practice: | |
| 70 | the number of excess bytes in an allocation depends on | |
| 71 | the underlying implementation. | |
| 847e0d88 | 72 | .PP |
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73 | The main use of this function is for debugging and introspection. |
| 74 | .SH SEE ALSO | |
| 75 | .BR malloc (3) |