mehdi_amini added a comment.
> I'd like to also see a testcase for the situation where we trigger the
> emission of a declaration with an available_externally definition and then
> find we need to promote it to a "full" definition:
Added!
================
Comment at: clang/lib/CodeGen/CodeGenModule.cpp:2448-2451
+ if (InitExpr) {
+ GV->setLinkage(llvm::GlobalValue::AvailableExternallyLinkage);
+ GV->setInitializer(EmitConstantInit(*InitDecl));
+ }
----------------
rsmith wrote:
> mehdi_amini wrote:
> > rsmith wrote:
> > > In order for this transformation to be correct, you need to know that the
> > > variable has static initialization, which means that it needs to formally
> > > have a constant initializer. You can use `D->isInitKnownICE()` to check
> > > this.
> > Done! But couldn't find how to express it as a test-case though.
> You'd need to use an initializer that we can constant-fold, such as:
>
> ```
> struct A {
> static const int n;
> };
> bool check() {
> assert(A::n == 0 && "already initialized!");
> return true;
> }
> const int A::n = (check() || true) ? 1 : 2;
> ```
But this wouldn't be an "available_externally". We need the initializer in the
class definition.
I tried multiple variant but couldn't get one that compile:
```
struct B {
static bool check() {
if (B::n == 0) return false;
return true;
}
// error: in-class initializer for static data member is not a constant
expression
static const int n = (B::check() || true) ? 1 : 2;
};
```
```
struct B {
static constexpr bool check() {
// "error: constexpr function never produces a constant expression"
return (B::n == 0 || true) ? false : true;
}
//"note: initializer of 'n' is not a constant expression"
static constexpr int n = (B::check() || true) ? 1 : 2;
};
```
================
Comment at: clang/lib/CodeGen/CodeGenModule.cpp:2445
+ !D->hasDefinition() && D->hasInit() &&
+ /* C++17 static constexpr are inlined */ !D->isInline() &&
+ !D->hasAttr<DLLImportAttr>() && D->isInitKnownICE()) {
----------------
rsmith wrote:
> Do we need to special-case this? Such declarations are definitions.
We don't! Simplified after rebasing and adapting after John's changes.
Repository:
rL LLVM
https://reviews.llvm.org/D34992
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