[PATCH] D69607: Add a feature to explain why some file gets included to the linker's output

[Peter Smith via Phabricator via llvm-commits]

peter.smith added a comment.

Thanks for the update, I'm happy with the explain output format.

One anomaly that I'm not sure is worth dealing with is the linkerscript GROUP command as used in libc.so

  GROUP ( /lib/libc.so.6 /usr/lib/libc_nonshared.a  AS_NEEDED ( /lib/ld-linux-armhf.so.3 ) )

I think that these will just end up as input files on the command line. Although they are non-obvious and implicitly included due to the linker script.



================
Comment at: lld/ELF/Explain.cpp:168
+
+  if (auto *sym = dyn_cast_or_null<Defined>(symtab->find(name))) {
+    outs() << "Explain: Symbol '" << name << "' is defined in file '"
----------------
Global symbols defined by a comdat group may cause some confusion as there will be multiple object files that define the symbol, but only one group that is selected that will match here. Not a lot that we can do here.  Perhaps if we knew that a symbol was defined in a group then we could print that out. "Explain: Symbol foo is defined in COMDAT group g, selected from from file foo.o". Perhaps wait and see if anyone does get confused.


================
Comment at: lld/ELF/Options.td:47
+    Eq<"explain", "Explain why a given file gets linked to the final binary">,
+    MetaVarName<"<path>">;
+
----------------
A suggestion:

```
Explain why a given object file gets linked in to the final binary. Objects can be specified by full path, or by a global symbol that they define. Objects defined in archives are specified by full/path/to/library(object) such as library.a(object.o).
```


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D69607/new/

https://reviews.llvm.org/D69607