Re: hey, who took away nested functions?
Re: hey, who took away nested functions?
- Subject: Re: hey, who took away nested functions?
- From: Dirk Stegemann <email@hidden>
- Date: Thu, 5 Jan 2006 21:09:00 +0200
Hi,
Am 05.01.2006 um 19:30 schrieb Matt Neuburg:
My code uses nested functions:
<http://developer.apple.com/documentation/DeveloperTools/gcc-4.0.1/
gcc/Neste
d-Functions.html>
It used to compile, but now it won't:
"nested functions are not supported on MacOSX"
What happened? Thx.
This topic has been discussed recently on Apple's "Xcode-users"
mailing list; from an Apple engineer:
-----snip-----
Re: gcc-4.0.1 = nested functions are not supported on MacOSX?
On Nov 10, 2005, at 10:24 PM, Daryn wrote:
The new xcode 2.2's gcc 4.0.1 compiler update has apparently
dropped support for nested functions. Apple's release notes for
gcc do not even mention this change... :(
Before I downgrade to gcc 4.0, is there a command line option to
re-enable nested functions?
Why were they disabled? Are they going to be re-enabled?
gcc's implementation of nested functions involves placing code on
the stack and then executing it. Stack execution is a common
operation in malicious code, particularly as a side effect of
buffer overflows. While the proper fix is of course to not make
buffer overflows possible in the first place, disabling stack
execution decreases the likelihood that a buffer overflow or other
stack-smashing attack will be exploitable.
In future releases of Mac OS X, we may disable stack execution.
(Obviously we'll have to keep binary compatibility in mind when or
if we do that.) Nested functions were disabled to help prepare for
that change.
As for whether nested functions will be re-enabled, if someone
contributes a patch to GCC to change the nested function
implementation to not rely on stack execution, presumably there'd
be a chance they'd be re-enabled.
Hope this helps,
Eric
-----snip-----
Regards,
Dirk Stegemann
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