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alloca() cannot check if the allocation is valid; mention the consequences.

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Obtained from:	OpenBSD
This commit is contained in:
Ruslan Ermilov 2006-09-05 16:30:11 +00:00
parent 3c03c7095e
commit 4d6ff03d50
1 changed files with 13 additions and 4 deletions
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17
lib/libc/stdlib/alloca.3
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@ -32,7 +32,7 @@
.\" @(#)alloca.3 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd June 4, 1993
.Dd September 5, 2006
.Dt ALLOCA 3
.Os
.Sh NAME
@ -57,9 +57,6 @@ return.
The
.Fn alloca
function returns a pointer to the beginning of the allocated space.
If the allocation failed, a
.Dv NULL
pointer is returned.
.Sh SEE ALSO
.Xr brk 2 ,
.Xr calloc 3 ,
@ -81,3 +78,15 @@ The
function
is machine and compiler dependent;
its use is discouraged.
.Pp
The
.Fn alloca
function is slightly unsafe because it cannot ensure that the pointer
returned points to a valid and usable block of memory.
The allocation made may exceed the bounds of the stack, or even go
further into other objects in memory, and
.Fn alloca
cannot determine such an error.
Avoid
.Fn alloca
with large unbounded allocations.