On 24/06/06 11:31AM, Patrick Steinhardt wrote:

We have recently noticed that our CI does not always notice variables
that may be used uninitialized. While it is expected that compiler
warnings aren't perfect, this one was a but puzzling because it was

s/but/bit/

rather obvious that the variable can be uninitialized.

Many compiler warnings unfortunately depend on the optimization level
used by the compiler. While `-O0` for example will disable a lot of
warnings altogether because optimization passes go away, `-O2`, which is
our default optimization level used in CI, may optimize specific code
away or even double down on undefined behaviour. Interestingly, this
specific instance that triggered the investigation does get noted by GCC
when using `-Og`.

While we could adapt all jobs to compile with `-Og` now, that would
potentially mask other warnings that only get diagnosed with `-O2`.
Instead, adapt the "linux-gcc-default" job to compile with `-Og`. This
job is chosen because it uses the "ubuntu:latest" image and should thus
have a comparatively recent compiler toolchain, and because we have
other jobs that use "ubuntu:latest" so that we do not loose coverage for

s/loose/lose/

warnings diagnosed only on `-O2` level.

To make it easier to set up the optimization level in our CI, add
support in our Makefile to specify the level via an environment
variable.

Signed-off-by: Patrick Steinhardt <redacted>
---

I was a little torn whether we really want to name the variable `O`
here because it feels so easy to set it by accident. We could rename
this to `OPTIMIZATION` or `OPTIMIZATION_LEVEL`, but that's quite a
mouthful.

Alternatively, if we don't want to have this variable in the first
place, then I'm also happy to adapt the script itself to pass the
optimization level via an argument.

I think the variable itself is fine, but for a name I think that either 
`OPTIMIZATION` or `OPTIMIZATION_LEVEL` would be a better pick. We have 
some other lengthy environment varible names so I don't think its too 
bad.

Otherwise, this looks good to me :)

-Justin