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| author | Michael Kerrisk <mtk.manpages@gmail.com> | 2006-11-25 04:13:11 +0000 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2006-11-25 04:13:11 +0000 |
| commit | be352a313b3be10f1800e26769b09023560c0c56 (patch) | |
| tree | d2ce8a21fd673c84e58a31c86d5033ad87e315bf | |
| parent | 266a5e9172c6d8c61545bacf445ecf2434e157df (diff) | |
| download | man-pages-be352a313b3be10f1800e26769b09023560c0c56.tar.gz | |
Add text describoing behaviour of the Linux brk() system call
and point out that the glibc brk() wrapper provides different behaviour.
Note that sbrk() is implemented as a library function in glibc that
calls the brk() system call.
| -rw-r--r-- | man2/brk.2 | 37 |
1 files changed, 34 insertions, 3 deletions
diff --git a/man2/brk.2 b/man2/brk.2 index 3d744fd2d1..08448a20bd 100644 --- a/man2/brk.2 +++ b/man2/brk.2 @@ -57,10 +57,17 @@ location of the program break. .SH "RETURN VALUE" On success, .BR brk () -returns zero, and +returns zero. +On error, \-1 is returned, and +.I errno +is set to +.BR ENOMEM . +(But see LINUX NOTES below.) + +On success, .BR sbrk () -returns a pointer to the start of the new area. On error, \-1 is returned, -and +returns a pointer to the start of the new area. +On error, \-1 is returned, and .I errno is set to .BR ENOMEM . @@ -82,6 +89,30 @@ Common are \fIint\fP, \fIssize_t\fP, \fIptrdiff_t\fP, \fIintptr_t\fP. .\" \fIptrdiff_t\fP (libc4, libc5, ulibc, glibc2.0, 2.1), .\" \fIintptr_t\fP (e.g. XPGv5, AIX, SunOS 5.8, 5.9, FreeBSD 4.7, NetBSD 1.6, .\" Tru64 5.1, glibc2.2). +.SH LINUX NOTES +The return value described above for +.BR brk () +is the behaviour provided by the glibc wrapper function for the Linux +.BR brk () +system call. +(On most other implementations, the return value from +.BR brk () +is the same.) +However, +the actual Linux system call returns the new program break on success. +On failure, the system call returns the current break +(thus for example, the call +.I brk(0) +can be used to obtain the current break). +The glibc wrapper function does some work to provide the 0 +and \-1 return values described above. + +On Linux, +.BR sbrk () +is implemented as a library function that uses the +.BR brk () +system call, and does some internal bookkeeping so that it can +return the old break value. .SH "SEE ALSO" .BR execve (2), .BR getrlimit (2), |