george.burgess.iv added inline comments.
================
Comment at: include/clang/Basic/Attr.td:753
@@ +752,3 @@
+ let Args = [IntArgument<"ElemSizeParam">, IntArgument<"NumElemsParam", 1>];
+ let TemplateDependent = 1;
+ let Documentation = [AllocSizeDocs];
----------------
aaron.ballman wrote:
> I don't see any C++ tests involving templates; can you add some?
Good catch
================
Comment at: test/SemaCXX/constant-expression-cxx11.cpp:1171
@@ -1170,3 +1170,3 @@
int l : n3; // expected-error {{constant expression}} expected-note {{read
of non-const variable}}
- int m : t.n; // expected-error {{constant expression}} expected-note {{read
of non-constexpr variable}}
+ int m : t.n; // expected-warning{{width of bit-field 'm' (42 bits)}}
};
----------------
aaron.ballman wrote:
> This change seems out of place for a test that doesn't use alloc_size
> anywhere. Can you explain why this test has changed?
Yup!
Clang's constexpr evaluator is conservative about `const` variables. If it kept
this attitude, `alloc_size` evaluation can't happen in non-constexpr contexts
in clang, even in cases like:
```
int foo() {
void *const p = malloc(10);
return __builtin_object_size(p, 0);
}
```
The change I made at ExprConstant.cpp:2789 (which Richard okayed when I talked
with him offline) makes the constexpr evaluator more willing to look at const
variables. With that, we can fold calls to `__builtin_object_size` like above
in clang.
It also means that there are a few cases outside of `alloc_size` where the
constexpr evaluator can be more aggressive. As it turns out, this is one of
them (as is the change in test/CodeGenCXX/global-init.cpp, IIRC)
http://reviews.llvm.org/D14274
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