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Re: [avr-libc-dev] making malloc() and free() reentrant safe

From: Russell Shaw
Subject: Re: [avr-libc-dev] making malloc() and free() reentrant safe
Date: Sun, 03 Jul 2005 18:57:09 +1000
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.8) Gecko/20050513 Debian/1.7.8-1

Joerg Wunsch wrote:
As Russell Shaw wrote:

What stdio functions call malloc?

Currently, fdevopen() ..., and the full-featured (...) versions of
vfscanf() and vfprintf(). ...

If the prolog stack-checking code gets done, then it could revert to
just using the stack.

Curious, what would happen if space on stack is tight then?

Then the normal behaviour of whatever happens now with short heap
space would happen. Atleast stack allocation is much faster and more
efficient than heap allocation. It is just idealogical unsound to use
the heap then throw it away in a short period of time;)

Right now, these functions simply skip any floating-point formatting
command if they cannot allocate the buffer, but continue to operate
normally for the remaining parts of the format string.  Also, the
buffer is *only* allocated when a floating-point command is
encountered first (during the current call to vfprintf()), so any
simple ``printf("Hi there, this is round %d\n", counter);'' would not
try to allocate the buffer at all.

Perhaps if the stack checking works, we could use alloca() instead?  I
think it's a builtin in GCC, so no additional code is needed, yet the
remaining behaviour would continue the way it is now.

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