clayborg added inline comments.
================
Comment at: lldb/source/Commands/CommandObjectThread.cpp:66
+ case 'c':
+ if (option_arg.getAsInteger(0, m_count) || (m_count < 0)) {
m_count = UINT32_MAX;
----------------
hawkinsw wrote:
> fixathon wrote:
> > If getAsInteger() fails we trigger the error path.
> > If getAsInteger() succeeds, but the fetched value (side-effect) is negative
> > we trigger the error path.
> >
> > I'm not 100% happy with my own code here..
> > getAsInteger() somewhat counter-intuitively returns *true* on failure, and
> > there's reliance on the short-circuit evaluation sequence-points for
> > correct evaluation when the 1st part is setting value via side-effect, and
> > the second validates it. This makes the expression somewhat hard to reason
> > about.
> >
> > Also mutating **m_count** directly may result in a non-atomic transition to
> > its new valid state in case when getAsInteger() fetches negative input,
> > which is less than perfect.
> >
> > That said, this code is just parsing command options, in a single-threaded
> > manner, so that shouldn't matter.
> I am not sure if this helps or not, but ...
>
> `getAsInteger` is the exact interface that the LLVM command-line parsing
> library uses for parsing numeric options. I looked through the codebase for
> other places that do the same type of operation to see if they use a
> different technique and could not find anything.
>
> To address your non-atomic comment, we could introduce a temporary? Given
> your description of how this code will be used (single-threaded), that seems
> like overkill?
>
> I am no expert and I hope that being part of the discussion is helpful.
Can we rely on ordering here? Or do we need to have two if statements, first
one for getAsInteger and a second nested on for "m_count < 0"? I would be safe
if we don't know the right answer
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D131983/new/
https://reviews.llvm.org/D131983
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