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1 | .\" Copyright (c) 2012 by Michael Kerrisk <mtk.manpages@gmail.com> |
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4 | .\" Permission is granted to make and distribute verbatim copies of this |
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24 | .\" |
| 25 | .TH MALLOC_USABLE_SIZE 3 2012-03-29 "GNU" "Linux Programmer's Manual" | |
| 26 | .SH NAME | |
| 27 | malloc_usable_size \- obtain size of block of memory allocated from heap | |
| 28 | .SH SYNOPSIS | |
| 29 | .B #include <malloc.h> | |
| 30 | ||
| 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. | |
| 48 | .SH CONFORMING TO | |
| 49 | This function is a GNU extension. | |
| 50 | .SH NOTES | |
| 51 | The value returned by | |
| 52 | .BR malloc_usable_size () | |
| 53 | may be greater than the requested size of the allocation because | |
| 54 | of alignment and minimum size constraints. | |
| 55 | Although the excess bytes can be overwritten by the application | |
| 56 | without ill effects, | |
| 57 | this is not good programming practice: | |
| 58 | the number of excess bytes in an allocation depends on | |
| 59 | the underlying implementation. | |
| 60 | ||
| 61 | The main use of this function is for debugging and introspection. | |
| 62 | .SH SEE ALSO | |
| 63 | .BR malloc (3) |