Messages in this thread Patch in this message | | | From | john.hubbard@gmail ... | Subject | [PATCH] mmap.2: MAP_FIXED is no longer discouraged | Date | Fri, 1 Dec 2017 18:16:26 -0800 |
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From: John Hubbard <jhubbard@nvidia.com>
MAP_FIXED has been widely used for a very long time, yet the man page still claims that "the use of this option is discouraged".
The documentation assumes that "less portable" == "must be discouraged".
Instead of discouraging something that is so useful and widely used, change the documentation to explain its limitations better.
Signed-off-by: John Hubbard <jhubbard@nvidia.com> --- While reviewing Michal Hocko's man page update for MAP_FIXED_SAFE, I noticed that MAP_FIXED was no longer reflecting the current situation, so here is a patch to bring it into the year 2017.
man2/mmap.2 | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/man2/mmap.2 b/man2/mmap.2 index 385f3bfd5..a5a8eb47a 100644 --- a/man2/mmap.2 +++ b/man2/mmap.2 @@ -222,8 +222,10 @@ part of the existing mapping(s) will be discarded. If the specified address cannot be used, .BR mmap () will fail. -Because requiring a fixed address for a mapping is less portable, -the use of this option is discouraged. +Software that aspires to be portable should use this option with care, keeping +in mind that the exact layout of a process' memory map is allowed to change +significantly between kernel versions, C library versions, and operating system +releases. .TP .B MAP_GROWSDOWN This flag is used for stacks. -- 2.15.1
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