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amount of available space increases as the break value increases. The available space is initialized to a value of zero, unless the break is lowered and then increased, as it may reuse the same pages in some unspecified way. The break value can be automatically rounded up to a size appropriate for the
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the amount of space allocated for the heap segment of the calling process. The change is made by resetting the program break of the process, which determines the maximum space that can be allocated. The program break is the address of the first location beyond the current end of the data region. The
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subroutine returns the prior value of the program break (if the available space is increased then this prior value also points to the start of the new area). If either subroutine is unsuccessful, a value of
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is an emulation and has a maximum allocation of 4 megabytes. On first call an area exactly this large is allocated to hold the simulated segment. When this limit is reached, −1 is returned and the
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were the only ways in which applications could acquire additional heap space; later versions allowed this to also be done using the
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Not every Unix-like system entertains the concept of having the user control the data segment. The
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is set and the allocated space remains unchanged if one or more of the following are true:
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operating systems to control the amount of memory allocated to the heap segment of the
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The requested change allocates more space than is allowed by a system-imposed maximum.
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is used to adjust the program break value by adding a possibly negative size, while
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parameter to zero to fetch the current value of the program break.
400:(2 ed.). X/Open Company Ltd., U.K. September 1994. p. 64
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Memory address § Address space in application programming
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is used to set the break value to the value of a pointer. Set
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v2 or POSIX.1-1998). They were removed in POSIX.1-2001.
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X/Open CAE Specification, System
Interfaces and Headers
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The requested change sets the break value to a value
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16:Basic memory management system calls used in Unix
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143:were considered legacy even by 1997 standards (
423:"brk, sbrk - change space allocation (LEGACY)"
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427:The Single UNIX ® Specification, Version 2
225:subroutine returns a value of 0, and the
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49:may contain suggestions.
34:may need to be rewritten
124:The brk and sbrk calls
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82:system calls
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43:You can help
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433:30 November
270:Error codes
120:Description
487:Categories
315:References
274:The error
258:is set to
77:are basic
404:9 October
335:9 October
216:increment
199:increment
90:Unix-like
47:talk page
298:See also
293:segment.
248:Mac OS X
196:intptr_t
157:#include
84:used in
473:"BRK.c"
359:13 June
94:process
460:Manual
450:brk(2)
429:. 1997
276:ENOMEM
260:ENOMEM
116:call.
99:malloc
45:. The
456:Linux
398:(PDF)
354:(PDF)
256:errno
237:errno
435:2019
406:2015
361:2018
337:2015
252:sbrk
227:sbrk
208:sbrk
190:sbrk
184:void
172:void
139:and
137:sbrk
113:mmap
108:sbrk
106:and
88:and
86:Unix
74:sbrk
71:and
264:brk
223:brk
212:brk
166:brk
163:int
141:brk
104:brk
68:brk
489::
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414:^
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232:−1
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
