[PATCH] D99456: [C++2b] Support size_t literals

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith added inline comments.


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Comment at: clang/include/clang/Basic/DiagnosticCommonKinds.td:198-200
+def err_size_t_literal_too_large: Error<
+  "%select{signed |}0'size_t' literal is out of range of possible "
+  "%select{signed |}0'size_t' values">;
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I wonder if it'd be better to say `'ssize_t'` instead of `signed 'size_t'` here? The latter sounds self-contradictory since `size_t` is an unsigned type.


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Comment at: clang/lib/Sema/SemaExpr.cpp:3895
       // be an unsigned int.
       bool AllowUnsigned = Literal.isUnsigned || Literal.getRadix() != 10;
 
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AntonBikineev wrote:
> I now begin to think that we should probably also prohibit things like 0x1234z to be implicitly interpreted as unsigned. Wdyt?
Table 8 says that a `z`-suffixed literal has type `ssize_t` (if the value fits) or `size_t` (otherwise), so I think taking `AllowUnsigned` into account is correct (although perhaps surprising).


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Comment at: clang/lib/Sema/SemaExpr.cpp:3997
       // does not fit in a signed long long, but has no U suffix.
       if (Ty.isNull()) {
         Diag(Tok.getLocation(), diag::ext_integer_literal_too_large_for_signed);
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AntonBikineev wrote:
> I think this branch should also be covered, since we probably don't want promotion from size_t to ULL but instead have a separate diagnostic that size_t is out-of-range. I've added another diagnostic and branch here.
Thanks, that makes sense to me. I agree that a `z`-suffixed literal should never have any type other than `size_t` or `ssize_t`; we don't want to fall back to `unsigned long long` as an extension.


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Comment at: clang/test/SemaCXX/size_t-literal.cpp:78
+
+  (void)0x80000000z; //cxx2b-32-error {{signed 'size_t' literal is out of range of possible signed 'size_t' values}}
+  (void)0x80000000uz;
----------------
This case looks valid to me.


Repository:
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  https://reviews.llvm.org/D99456/new/

https://reviews.llvm.org/D99456