Disable all optimization options in GCC

[Jonathan Wakely]

On 22 October 2015 at 15:46, Mohamed Boussaa <mohamedboussaa3@gmail.com> wrote:
> To answer my question, I have made some conclusions and assumptions:
>
> So let me say that compiling with O0 does not mean that no
> optimizations will be applied.

Wrong.

> Options that reduce compilation time
> and make debugging better will be turned on.

Wrong. At -O0 options that would _increase_ compilation time are _not_
turned on.


> In other words, O0 is optimizing in the level of compilation. Produced
> binaries are not optimized in order to ease debugging process.

I don't know what this means.

> I give an example: This option is enabled at O0 level
>
> -faggressive-loop-optimizations

No it isn't.

> In GCC documentation:
>
> This option tells the loop optimizer to use language constraints to
> derive bounds for the number of iterations of a loop. This assumes
> that loop code does not invoke undefined behavior by for example
> causing signed integer overflows or out-of-bound array accesses. The
> bounds for the number of iterations of a loop are used to guide loop
> unrolling and peeling and loop exit test optimizations. This option is
> enabled by default.
>
> So for GCC 4.8.x, there are almost 50 options turned on by default.

Wrong.

> Can someone confirm that?

No, because you're wrong, as Andrew has said twice.