hoy added inline comments.
================
Comment at: clang/test/CodeGen/unique-internal-linkage-names-dwarf.c:34-39
+static int go(a) int a;
+{
+ return glob + a;
+}
+
+
----------------
dblaikie wrote:
> hoy wrote:
> > dblaikie wrote:
> > > hoy wrote:
> > > > dblaikie wrote:
> > > > > hoy wrote:
> > > > > > dblaikie wrote:
> > > > > > > Does this need to be down here? Or would the code be a well
> > > > > > > exercised if it was up next to the go declaration above?
> > > > > > Yes, it needs to be here. Otherwise it will just like the function
> > > > > > `bar` above that doesn't get a uniquefied name. I think moving the
> > > > > > definition up to right after the declaration hides the declaration.
> > > > > Not sure I follow - do you mean that if the go declaration and go
> > > > > definition were next to each other, this test would (mechanically
> > > > > speaking) not validate what the patch? Or that it would be less
> > > > > legible, but still mechanically correct?
> > > > >
> > > > > I think it would be (assuming it's still mechanically correct) more
> > > > > legible to put the declaration next to the definition - the comment
> > > > > describes why the declaration is significant/why the definition is
> > > > > weird, and seeing all that together would be clearer to me than
> > > > > spreading it out/having to look further away to see what's going on.
> > > > When the `go` declaration and `go` definition were next to each other,
> > > > the go function won't get a uniqufied name at all. The declaration will
> > > > be overwritten by the definition. Only when the declaration is seen by
> > > > others, such the callsite in `baz`, the declaration makes a difference
> > > > by having the callsite use a uniqufied name.
> > > >
> > > >
> > > Ah! Interesting, good to know.
> > >
> > > Is that worth supporting, I wonder? I guess it falls out for free/without
> > > significant additional complexity. I worry about the subtlety of the
> > > additional declaration changing the behavior here... might be a bit
> > > surprising/subtle. But maybe no nice way to avoid it either.
> > It would be ideal if user never writes code like that. Unfortunately it
> > exists with legacy code (such as mysql). I think it's worth supporting it
> > from AutoFDO point of view to avoid a silent mismatch between debug linkage
> > name and real linkage name.
> Oh, I agree that we shouldn't mismatch debug info and the actual symbol name
> - what I meant was whether code like this should get mangled or not when
> using unique-internal-linkage names.
>
> I'm now more curious about this:
>
> > When the `go` declaration and `go` definition were next to each other, the
> > go function won't get a uniqufied name at all.
>
> This doesn't seem to happen with the `__attribute__((overloadable))`
> attribute, for instance - so any idea what's different about uniquification
> that's working differently than overloadable?
>
> ```
> $ cat test.c
> __attribute__((overloadable)) static int go(a) int a; {
> return 3 + a;
> }
> void baz() {
> go(2);
> }
> $ clang-tot test.c -emit-llvm -S -o - | grep go
> %call = call i32 @_ZL2goi(i32 2)
> define internal i32 @_ZL2goi(i32 %a) #0 {
> ```
Good question. I'm not sure what's exactly going on but it looks like with the
overloadable attribute, the old-style definition is treated as having
prototype. But if you do this:
```
__attribute__((overloadable))
void baz() {}
```
then there's the error:
```
error: 'overloadable' function 'baz' must have a prototype
void baz() {
```
`void baz() {` does not come with a prototype. That's for sure. Sounds like
`int go(a) int a {;` can have a prototype when it is loadable. I'm wondering
why it's not always treated as having prototype, since the parameter type is
there.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D98799/new/
https://reviews.llvm.org/D98799
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