labath added inline comments.
================
Comment at: lldb/source/Plugins/Process/Utility/InferiorCallPOSIX.cpp:54
+ if (sc_list.GetContextAtIndex(i, sc) &&
+ (sc.symbol->IsExternal() || sc.symbol->IsWeak())) {
const uint32_t range_scope =
----------------
aadsm wrote:
> labath wrote:
> > clayborg wrote:
> > > aadsm wrote:
> > > > clayborg wrote:
> > > > > Why are we checking "IsWeak()" here?
> > > > A weak symbol is also an external symbol, but it's weak in the sense
> > > > that another external symbol with the same name will take precedence
> > > > over it (as far as I understood).
> > > I think we only need to check for external here. Any weak symbol will
> > > also need to be external, but if it isn't we don't want that symbol.
> > Your understanding is correct, at least at the object file level -- I'm not
> > sure whether `IsWeak()` implies `IsExternal()` inside lldb. However, I
> > would actually argue for removal of IsWeak() for a different reason -- any
> > weak definition of mmap is not going to be used by the process since libc
> > already has a strong definition of that symbol.
> >
> > If we really end up in a situation where we only have a weak mmap symbol
> > around, then this is probably a sufficiently strange setup that we don't
> > want to be randomly calling that function.
> All (with the exception of the one overriden by the leak sanitizer) mmap
> symbols in the symbol table are Weak bound but none are External bound, this
> was the main reason that lead me to investigate the difference between the
> two.
>
> Not sure how to check how lldb interprets the Weak overall, but I think it
> kind of does, because that's what I saw when I dumped the symbol table:
> ```
> (lldb) target modules dump symtab libc.so.6
> Debug symbol
> |Synthetic symbol
> ||Externally Visible
> |||
> Index UserID DSX Type File Address/Value Load Address Size
> Flags Name
> ------- ------ --- --------------- ------------------ ------------------
> ------------------ ---------- ----------------------------------
> ...
> [ 6945] 6947 X Code 0x000000000010b5e0 0x00007ffff69db5e0
> 0x00000000000000f9 0x00000012 __mmap
> ...
> ```
>
> Another solution I thought was to add a IsLocal to the Symbol (and use
> !IsLocal) but then not really sure how to implement this for all Symbols not
> ELFSymbol.
Interesting. I guess I should have verified my assumptions. With that in mind,
I think checking for both weak and external (strong) symbols is fine.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D87868/new/
https://reviews.llvm.org/D87868
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