aaron.ballman added inline comments.
================
Comment at: clang/test/Analysis/cfg.cpp:570
}
+// CHECK-LABEL: void vla_simple(int x)
----------------
NoQ wrote:
> balazske wrote:
> > balazske wrote:
> > > aaron.ballman wrote:
> > > > Can you also add tests for:
> > > > ```
> > > > int vla_unevaluated(int x) {
> > > > // Evaluates the ++x
> > > > sizeof(int[++x]);
> > > > // Does not evaluate the ++x
> > > > _Alignof(int[++x]);
> > > > _Generic((int(*)[++x])0, default : 0);
> > > >
> > > > return x;
> > > > }
> > > > ```
> > > >
> > > > Also, it's a bit strange to find these VLA tests in a .cpp file. VLAs
> > > > are a C++ extension and we should have some testing for them for
> > > > constructs that are C++-specific, but I would have expected many of
> > > > these tests to be in a C file instead.
> > > Could be there platforms (on buildbot?) where the VLA code (in cpp file)
> > > does not compile? Is it worth to have a test with VLA type alias then?
> > I have this output for the test above (without the new code), is it correct?
> > (The `++` seems to be evaluated for the `alignof` statement too.)
> > ```
> > int vla_unevaluated(int x)
> > [B2 (ENTRY)]
> > Succs (1): B1
> >
> > [B1]
> > 1: x
> > 2: ++[B1.1]
> > 3: [B1.2] (ImplicitCastExpr, LValueToRValue, int)
> > 4: sizeof(int [++x])
> > 5: x
> > 6: ++[B1.5]
> > 7: [B1.6] (ImplicitCastExpr, LValueToRValue, int)
> > 8: alignof(int [++x])
> > 9: 0
> > 10: x
> > 11: [B1.10] (ImplicitCastExpr, LValueToRValue, int)
> > 12: return [B1.11];
> > Preds (1): B2
> > Succs (1): B0
> >
> > [B0 (EXIT)]
> > Preds (1): B1
> >
> > ```
> > Could be there platforms (on buildbot?) where the VLA code (in cpp file)
> > does not compile? Is it worth to have a test with VLA type alias then?
>
> That's unlikely; the problems with VLAs in C++ are IIRC about the bureaucracy
> of the Standard (i.e., they couldn't solve enough cornercases, like whether
> `T<int[x]>` and `T<int[y]>` the same template when `x == y` at run-time?),
> not about platform support.
> Could be there platforms (on buildbot?) where the VLA code (in cpp file) does
> not compile? Is it worth to have a test with VLA type alias then?
I think the type alias test is a good idea (as are any other C++-specific
tests) because we support VLAs in C++ mode as an extension, my concern was more
that this is a C feature and so if I was hunting for tests for VLAs, I'd look
in a .c file first. It's not a huge concern, more like a style nit.
> (The ++ seems to be evaluated for the alignof statement too.)
That seems wrong per C17 6.5.3.4p3. It also doesn't seem to match the behavior
I'm seeing: https://godbolt.org/z/rVaGnb
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D77809/new/
https://reviews.llvm.org/D77809
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