When did 'pragma optimize' become available?

[Jeffrey Walton]

On Mon, Jul 13, 2015 at 3:14 AM, Markus Trippelsdorf
<markus@trippelsdorf.de> wrote:
> On 2015.07.12 at 20:32 -0400, Jeffrey Walton wrote:
>> I've got a crash under GCC 4.9/x86_64 when using -O3. (The crash is
>> related to an array that's 64-bit aligned, but GCC selects the vmovdqa
>> instruction, which has 128-bit alignment requirements.)
>>
>> It was easy enough to back-off optimizations:
>>
>>     #pragma GCC optimize push
>>     #pragma GCC optimize ("-O2")
>>
>>     void xorbuf(byte *buf, const byte *mask, size_t count)
>>     {
>>        ...
>>     }
>>     #pragma GCC optimize pop
>>
>
> This is a bad idea in general, because "pragma GCC optimize" is meant as
> a compiler debugging aid only. It should _not_ be used in production
> code.
> Please fix the underlying issue instead (, or open a bug for it).

We cleared the issue; thanks for the advice.

I have one more question related to the use of '#pragma GCC optimize'.
I have a zeroizer that must execute due to Certification and
Accreditation (C&A) requirements. When the zeroizer is removed as a
dead store, the compiler folks usually say, "but you asked for
optimizations...".

If we cannot use '#pragma GCC optimize' to turn off the optimizer for
a function, then how do we tell the compiler to *not* remove the code?