[Gstreamer-bugs] [Bug 135640] New - Usage of alloca is not portable, and breaks under NetBSD

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http://bugzilla.gnome.org/show_bug.cgi?id=135640

Changed by jmmv at menta.net.

--- shadow/135640	Fri Feb 27 17:27:40 2004
+++ shadow/135640.tmp.9078	Fri Feb 27 17:27:40 2004
@@ -0,0 +1,49 @@
+Bug#: 135640
+Product: GStreamer
+Version: HEAD CVS
+OS: NetBSD
+OS Details: 
+Status: NEW   
+Resolution: 
+Severity: normal
+Priority: Normal
+Component: gst-plugins
+AssignedTo: gstreamer-maint at bugzilla.gnome.org                            
+ReportedBy: jmmv at menta.net               
+QAContact: gstreamer-maint at bugzilla.gnome.org
+TargetMilestone: HEAD
+URL: 
+Summary: Usage of alloca is not portable, and breaks under NetBSD
+
+The file gst/interleave/interleave.c uses the alloca(3) function.  Even 
+though, the code assumes it's present, and also assumes the alloca.h 
+header file exists.  The later is the one causing problems in NetBSD, 
+because the header file to use is stdlib.h, not the missing alloca.h. 
+ 
+According to NetBSD's alloca(3) manpage: 
+ 
+     The alloca() function is machine dependent; its use is discouraged. 
+ 
+     The 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 alloca() cannot determine such an 
+     error.  Avoid alloca() with large unbounded allocations. 
+ 
+Therefore, I suggest using malloc instead of alloca, since the former is 
+standard and less problematic.  alloca is used in just one place, so 
+converting it to malloc should be easy (if I've understood alloca's 
+functionality properly).  The attached patch attempts to do this. 
+ 
+If you still want to use alloca, then a check in configure is required.  
+The right one to use is AC_FUNC_ALLOCA.  Using it implies doing several 
+other changes (and also implies having to provide a workaround in case 
+it's missing, so we are back to switching to malloc), so I've not done 
+this.  See autoconf's info manual for more information about this topic.  
+(Please note that the manual does not mention stdlib.h containing 
+alloca's prototype, so you should #include this file in the source 
+unconditionally to be sure it gets defined sometime, in case it's there 
+and not in alloca.h.)