[PATCH] D43658: Make undefined symbol in DSO to pull out object files from archive files.

[Rui Ueyama via llvm-commits]

Oh sorry, maybe I should have put .so before .a in the test case. I'll fix
that.

On Thu, Feb 22, 2018 at 5:05 PM, Rafael Avila de Espindola <
rafael.espindola at gmail.com> wrote:

> I get errors from both gold and bfd if I try to link the included
> testcase. Maybe it has been reduced a bit too much?
>
> Cheers,
> Rafael
>
> Rui Ueyama via Phabricator <reviews at reviews.llvm.org> writes:
>
> > ruiu created this revision.
> > ruiu added a reviewer: rafael.
> > Herald added subscribers: arichardson, emaste.
> >
> > We have an internal program that does't link without this patch. I don't
> > know of any open-source program that needs this, but there might be.
> > Since this patch improves compatibility with GNU linkers with a few lines
> > of code, I think it's worth to be committed.
> >
> > The problem is about undefined symbols in DSOs. Some programs depend on
> > the GNU linkers' behavior that they pull out object files from archive
> > files to resolve undefined symbols in DSOs. We already allow that kind of
> > "reverse" dependency (from DSOs to the main executable) for regular
> > symbols, in particular, for "__progname" symbol, but that didn't work
> > if the symbol is in an archive file. This patch is to make it work.
> >
> >
> > https://reviews.llvm.org/D43658
> >
> > Files:
> >   lld/ELF/SymbolTable.cpp
> >   lld/test/ELF/shlib-undefined-archive.s
> >
> >
> > Index: lld/test/ELF/shlib-undefined-archive.s
> > ===================================================================
> > --- /dev/null
> > +++ lld/test/ELF/shlib-undefined-archive.s
> > @@ -0,0 +1,18 @@
> > +# REQUIRES: x86
> > +
> > +# Undefined symbols in a DSO should pull out object files from archives
> > +# to resolve them.
> > +
> > +# RUN: echo '.globl foo' | llvm-mc -filetype=obj
> -triple=x86_64-linux-gnu -o %t1.o -
> > +# RUN: ld.lld -shared -o %t.so %t1.o
> > +
> > +# RUN: llvm-mc -filetype=obj -triple=x86_64-linux-gnu -o %t2.o %s
> > +# RUN: llvm-ar cru %t.a %t2.o
> > +# RUN: ld.lld -o %t.exe %t.a %t.so
> > +# RUN: llvm-nm -D %t.exe | FileCheck %s
> > +
> > +# CHECK: T foo
> > +
> > +.globl foo
> > +foo:
> > +  ret
> > Index: lld/ELF/SymbolTable.cpp
> > ===================================================================
> > --- lld/ELF/SymbolTable.cpp
> > +++ lld/ELF/SymbolTable.cpp
> > @@ -599,9 +599,14 @@
> >    for (InputFile *F : SharedFiles) {
> >      for (StringRef U : cast<SharedFile<ELFT>>(F)->getUndefinedSymbols())
> {
> >        Symbol *Sym = find(U);
> > -      if (!Sym || !Sym->isDefined())
> > +      if (!Sym)
> >          continue;
> > -      Sym->ExportDynamic = true;
> > +      if (auto *L = dyn_cast<Lazy>(Sym))
> > +        if (InputFile *File = L->fetch())
> > +          addFile<ELFT>(File);
> > +
> > +      if (Sym->isDefined())
> > +        Sym->ExportDynamic = true;
> >      }
> >    }
> >  }
> >
> >
> > Index: lld/test/ELF/shlib-undefined-archive.s
> > ===================================================================
> > --- /dev/null
> > +++ lld/test/ELF/shlib-undefined-archive.s
> > @@ -0,0 +1,18 @@
> > +# REQUIRES: x86
> > +
> > +# Undefined symbols in a DSO should pull out object files from archives
> > +# to resolve them.
> > +
> > +# RUN: echo '.globl foo' | llvm-mc -filetype=obj
> -triple=x86_64-linux-gnu -o %t1.o -
> > +# RUN: ld.lld -shared -o %t.so %t1.o
> > +
> > +# RUN: llvm-mc -filetype=obj -triple=x86_64-linux-gnu -o %t2.o %s
> > +# RUN: llvm-ar cru %t.a %t2.o
> > +# RUN: ld.lld -o %t.exe %t.a %t.so
> > +# RUN: llvm-nm -D %t.exe | FileCheck %s
> > +
> > +# CHECK: T foo
> > +
> > +.globl foo
> > +foo:
> > +  ret
> > Index: lld/ELF/SymbolTable.cpp
> > ===================================================================
> > --- lld/ELF/SymbolTable.cpp
> > +++ lld/ELF/SymbolTable.cpp
> > @@ -599,9 +599,14 @@
> >    for (InputFile *F : SharedFiles) {
> >      for (StringRef U : cast<SharedFile<ELFT>>(F)->getUndefinedSymbols())
> {
> >        Symbol *Sym = find(U);
> > -      if (!Sym || !Sym->isDefined())
> > +      if (!Sym)
> >          continue;
> > -      Sym->ExportDynamic = true;
> > +      if (auto *L = dyn_cast<Lazy>(Sym))
> > +        if (InputFile *File = L->fetch())
> > +          addFile<ELFT>(File);
> > +
> > +      if (Sym->isDefined())
> > +        Sym->ExportDynamic = true;
> >      }
> >    }
> >  }
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180222/03958ca2/attachment-0001.html>