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Fixed bug #855 Ludwig Nussel 2009-10-18 06:31:52 PDT an mprotect call was added to fix bug 528. However that results in a buffer that allows writing and code execution. Ie the no-execute security features of modern operating systems are defeated this way. Two mprotect calls are needed. One to make the buffer executable but not writeable when done and another one to make the buffer writeable again if the content needs to be changed.
author Sam Lantinga <slouken@libsdl.org>
date Sun, 18 Oct 2009 17:31:37 +0000
parents 355632dca928
children
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<HTML
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>SDL_CreateSemaphore</TITLE
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><H1
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>SDL_CreateSemaphore</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN7936"
></A
><H2
>Name</H2
>SDL_CreateSemaphore&nbsp;--&nbsp;Creates a new semaphore and assigns an initial value to it.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN7939"
></A
><H2
>Synopsis</H2
><DIV
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><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"
#include "SDL_thread.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>SDL_sem *<B
CLASS="FSFUNC"
>SDL_CreateSemaphore</B
></CODE
>(Uint32 initial_value);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7946"
></A
><H2
>Description</H2
><P
><TT
CLASS="FUNCTION"
>SDL_CreateSemaphore()</TT
> creates a new semaphore and
initializes it with the value <TT
CLASS="PARAMETER"
><I
>initial_value</I
></TT
>.
Each locking operation on the semaphore by
<A
HREF="sdlsemwait.html"
>SDL_SemWait</A
>,
<A
HREF="sdlsemtrywait.html"
>SDL_SemTryWait</A
> or
<A
HREF="sdlsemwaittimeout.html"
>SDL_SemWaitTimeout</A
>
will atomically decrement the semaphore value. The locking operation will be blocked
if the semaphore value is not positive (greater than zero). Each unlock operation by
<A
HREF="sdlsempost.html"
>SDL_SemPost</A
>
will atomically increment the semaphore value.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7955"
></A
><H2
>Return Value</H2
><P
>Returns a pointer to an initialized semaphore or
<SPAN
CLASS="RETURNVALUE"
>NULL</SPAN
> if there was an error.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN7959"
></A
><H2
>Examples</H2
><P
><PRE
CLASS="PROGRAMLISTING"
>SDL_sem *my_sem;

my_sem = SDL_CreateSemaphore(INITIAL_SEM_VALUE);

if (my_sem == NULL) {
        return CREATE_SEM_FAILED;
}</PRE
></P
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><A
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></A
><H2
>See Also</H2
><P
><A
HREF="sdldestroysemaphore.html"
><TT
CLASS="FUNCTION"
>SDL_DestroySemaphore</TT
></A
>,
<A
HREF="sdlsemwait.html"
><TT
CLASS="FUNCTION"
>SDL_SemWait</TT
></A
>,
<A
HREF="sdlsemtrywait.html"
><TT
CLASS="FUNCTION"
>SDL_SemTryWait</TT
></A
>,
<A
HREF="sdlsemwaittimeout.html"
><TT
CLASS="FUNCTION"
>SDL_SemWaitTimeout</TT
></A
>,
<A
HREF="sdlsempost.html"
><TT
CLASS="FUNCTION"
>SDL_SemPost</TT
></A
>,
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><TT
CLASS="FUNCTION"
>SDL_SemValue</TT
></A
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