tahonermann added inline comments.
================
Comment at: clang/lib/AST/Interp/ByteCodeExprGen.cpp:1098-1099
+
+ unsigned N = SL->getLength();
+ for (size_t I = 0; I != NumElems; ++I) {
+ uint32_t CodePoint = I < N ? SL->getCodeUnit(I) : 0;
----------------
tahonermann wrote:
> Aren't `N` and `NumElems` guaranteed to have the same value here? Both are
> derived from `SL`. The code seems to be written with the expectation that
> `NumElems` corresponds to the number of elements to be iniitialized in the
> target array.
I see the change to now use the minimum of `SL->getLength()` and
`CAT->getSize().getZExtValue()`. Based on https://godbolt.org/z/5sTWExTac this
looks to be unnecessary. When a string literal is used as an array initializer,
it appears that the type of the string literal is adjusted to match the size of
the array being initialized. I suggest using only
`CAT->getSize().getZExtValue()` and adding a comment that this code depends on
that adjustment.
================
Comment at: clang/test/AST/Interp/literals.cpp:354-359
+ constexpr char foo[12] = "abc";
+ static_assert(foo[0] == 'a', "");
+ static_assert(foo[1] == 'b', "");
+ static_assert(foo[2] == 'c', "");
+ static_assert(foo[3] == 0, "");
+ static_assert(foo[11] == 0, "");
----------------
tahonermann wrote:
> aaron.ballman wrote:
> > I'd like to see some tests for the other encodings, as well as a test with
> > embedded null characters in the literal.
> >
> > Testing a string literal that's longer than the array is something we
> > should think about. That code is ill-formed in C++, so I don't think we can
> > add a test for it yet, but it's only a warning in C.
> I agree with Aaron's requests. Please also extend the test to include a
> `char` element that would be negative for a `signed` 8-bit `char`. Something
> like:
> constexpr char foo[12] = "abc\xff";
> ...
> #if defined(__CHAR_UNSIGNED__) || __CHAR_BIT__ > 8
> static_assert(foo[3] == 255, "");
> #else
> static_assert(foo[3] == -1, "");
> #endif
>
> A couple of more tests to add:
> - One where the string literal has the same length (including the implicit
> terminator) as the array; to ensure that the implicit terminator is properly
> accounted for.
> - One where the target array size is deduced from the string literal; to
> ensure there are no dependencies on an explicit array size.
These cases all look to have been added now. Thank you!
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D137488/new/
https://reviews.llvm.org/D137488
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