[chbot] gcc experts: Is there a flag/symbol available to see current optimisations?

[Simeon Pilgrim]

Given the request was related to being able to print in the code the
optimization level, this SO question seems better suited:
https://stackoverflow.com/questions/31718637/determine-optimization-level-in-preprocessor

On Sun, 28 Jun 2020 at 19:35, Helmut Walle <helmut.walle at gmail.com> wrote:

> Assuming you only have the binary executable, the question, while
> conceptually simple, actually
> is complex in practice. You could disassemble the binary and look for
> signs of optimisation (or
> the absence of the respective signs) there... but the obvious problem with
> that is that if you
> "optimise" something with a certain switch, and the input doesn't yield
> anything in that regard,
> the output will be exactly the same as without that switch... So you would
> expect to get more
> mileage out of this approach for more complex programs, as the probability
> of something actually
> being achieved by optimisation is greater than for something that is so
> quick and simple that
> optimisation doesn't make a difference to the output.
>
> Now this is all very nice in theory, but in practice it would still mean
> that you would have to
> create the analytics tooling yourself (unless someone has already done it).
>
> All of that being said, the question is not exactly new - see here for
> some quick discussions of
> some of the relevant points:
>
>
> https://stackoverflow.com/questions/189350/detect-gcc-compile-time-flags-of-a-binary/340828
>
> https://stackoverflow.com/questions/9307960/find-out-compilation-optimization-flag-from-executable
>
> Why does it even matter?
>
> Kind regards,
>
> Helmut.
>
>
> On 28/06/2020 18:47, Charles Manning wrote:
> > Hi All
> >
> > I want to be able to tell in some logs what optimisation level was used
> to compile some code.
> >
> > eg.
> >   printf("This code was optimised with %s\n", omptimisation_string());
> >
> > And this would print:
> > "This code was optimised with -Os\n" or whatever.
> >
> > Does anyone know of such a thing in gcc?
> >
> > Thanks.
> >
> >
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