[PATCH] D86909: [lld-macho] Initial support for common symbols

[Jez Ng via Phabricator via llvm-commits]

int3 added inline comments.


================
Comment at: lld/MachO/SymbolTable.cpp:85
+    if (auto *common = dyn_cast<CommonSymbol>(s)) {
+      if (size >= common->size) {
+        common->file = file;
----------------
int3 wrote:
> MaskRay wrote:
> > int3 wrote:
> > > int3 wrote:
> > > > int3 wrote:
> > > > > MaskRay wrote:
> > > > > > This is strange. Is it `>`?
> > > > > This is intentional. The `same-size.s` test verifies this behavior, and can be used to check that ld64 does the same thing.
> > > > actually, I may have messed up the test...
> > > okay fixed. ld64 actually takes the smaller alignment if the sizes are equal. still different from lld-ELF's behavior though...
> > This rule is hard to believe...
> > 
> > A larger alignment imposes a larger requirement. Shouldn't the larger alignment be used?
> > 
> > In ELF, size and align are separately considered.
> I dunno... ld64 really does seem to behave like this. I haven't found the corresponding part of its code that handles common symbol resolution though
> 
> ld64 does take a `-max_default_common_align` option, and I double-checked to make sure that the max was high enough that it wouldn't interfere with our test
My bad... my initial test was wrong in two places, but the `>=` was actually correct. I've fixed the test and reverted the behavior to the original. I'm fairly confident that it is correctly replicating ld64's behavior now, though I do agree it's a little weird


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D86909/new/

https://reviews.llvm.org/D86909