[Simh] Recent build crashes on OSX

[Paul Koning]

> On Feb 17, 2016, at 3:01 PM, Howard Bussey <howard.bussey at gmail.com> wrote:
> 
> Googling “Process PTE …” shows this occurred before:
> 
> http://mailman.trailing-edge.com/pipermail/simh/2010-May/010760.html
> 
> The suggestion was to try turning off optimization when compiling simh…

In that case, gcc is the compiler.  In the case Michael mentioned, it's LLVM.  So the conclusion is that it's a SimH bug, non-compliant code that gets caught by modern optimizing compilers.

Turning on GCC warnings may help; a lot of issues of this kind are reported as warnings if you build with -Wall.  I don't see anything interesting when I try that on OSX, but that's LLVM.  When I try it on Linux, I get a bunch of possible uninitialized variables -- those are sometimes false warnings but worth looking at.  More interesting is a bunch of "does break strict-aliasing rules".  Those indicate incorrect (not ANSI compliant) code that you used to be able to get away with, but can't any longer when optimization is enabled.  The correct way to handle those errors is to fix the code, not to disable the warning or the optimization (as is done by some other software teams).

More info can be found here: https://homes.cs.washington.edu/~akcheung/papers/apsys12.pdf -- a very good article that all C programmers should read.

	paul