Re: [autoconf] Problems Configuring (C Compiler cannot produce executables)

[Mike Frysinger]

On Wednesday 22 August 2012 18:28:52 Russ Allbery wrote:
> special exceptions.  Being able to turn of executable stack as at least
> another easily-accessible option is an interesting idea, and I may raise
> that on debian-devel.  (Although it can be a little hard to predict which
> packages need that.

it's trivial to locate:
        readelf -lW /bin/bash | grep GNU_STACK
if it's set as RWE, that's bad.  if the ELF lacks a GNU_STACK, that's bad.

or use scanelf to quickly find all ELFs on the system:
        scanelf /{,usr/}{,s}bin -qry -F '%e %F'

very few packages in Gentoo have these (69 out of ~15k), and almost all of 
those are either binary-only packages or games.

> Hm, and I seem to recall that GCC does some stuff with executable stack
> automatically.)

yes, trampolines can trigger executable stacks, but usually that only happens 
with nested functions, which is usually pretty easy to rewrite to avoid.  i 
think i've seen maybe two packages where this came up (one of which was grub).

> > Autoconf could use ac_cflags as it being used now(?) and save
> > ac_warnings for later use (by Automake?) when real source files are
> > compiled.
> 
> It would be nice to have some additional support directly in standard
> Autoconf macros for handling compiler warning flags, although I suspect
> there is stuff in both the macro archive and in gnulib.

yes, the autoconf-archive has a bunch already written
-mike

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