Properly controlling CFLAGS/CXXFLAGS

[Joseph J. Damato]

> Garrett Cooper wrote:
> 
> With '-O2' and better, '-fstrict-aliasing' is the default in newer 
> versions of GCC, AFAIK, but people tend to switch it off because it 
> apparently breaks too many software packages.  Or at least those whose 
> code base dates back to times where '-fno-strict-aliasing' was the default
> and people got away with certain nasty coding hacks that no longer work
> with '-fstrict-aliasing'.
> 

Well, -fno-strict-aliasing is pretty useful, especially if you want to do things with floating point. Not all code which requires -fno-strict-aliasing has "nasty coding hacks." 

As GCC says, the results are undefined when the flag is not passed. I have personally seen code that "looks" right but which results in very odd behavior with -O2, but works fine with any other optimization level. 

In situations like this, the flag is useful.

Joe Damato