Question about memory allocation in ifcvt.c

[thorsten]

Hello all,

this might be a noob Question but perhaps someone is so kind as to shed 
some light...

using gcc-4.5.4 to build large files (as in wireshark or qemu) with 
Optimizations enabled (in my case -O2 -pipe -march=core2 
-fomit-frame-pointer) I get segmentation faults due to Stack limits, 
when using the standard stacksize on linux.

I figured out that ifcvt.c uses alloca to reserve mem on the stack. this 
is the point where the segmentation fault occurs.

So beeing curious, I changed alloca to xmalloc to use the heap instead 
of the stack, thinking this is likely to cause a huge penalty in 
compile-speed. But comparing both the gcc-alloca and gcc-xmalloc the 
compiletimes do not differ significantly. And the gcc-xmalloc does not 
crash anymore due to limited stackspace.

So here is my question: What is the reason for using alloca (Stack) 
instead of xmalloc (heap) in ifcvt.c? I have seen, that also gcc-4.7.2 
still uses alloca.

Thanks!

Thorsten