Fix linker-defined symbols possibly not being defined when -wrap is used

[thomasanderson]

Summary

Fixes https://bugs.llvm.org/show_bug.cgi?id=40134

addWrappedSymbols() must be called before addReservedSymbols() because the
latter only defines reserved symbols when they are undefined in the symbol
table. If addWrappedSymbols() is called after, then addUndefined() is called
which may lazily pull in more object files that could reference reserved
symbols.

[thakis]

Can you add a test to lld/test/ELF?

[thomasanderson]

Can you add a test to lld/test/ELF?

Done. Added test fails without change; all tests pass with change

[ruiu]

There's no test file named after a bug number in lld test suite, so you should avoid doing that for consistency.

[thomasanderson]

There's no test file named after a bug number in lld test suite, so you should avoid doing that for consistency.

Done! (There are a few that managed to sneak in: ELF/pr34660.s ELF/pr34872.s ELF/pr36475.s ELF/pr37735.s)

[thomasanderson]

Ping. Is this good to land now?

[ruiu]

LGTM. Please submit.

lld/trunk/ELF/Driver.cpp

template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
   if (Args.hasArg(OPT_exclude_libs))
     excludeLibs<ELFT>(Args);
 
   // Create ElfHeader early. We need a dummy section in
   // addReservedSymbols to mark the created symbols as not absolute.
   Out::ElfHeader = make<OutputSection>("", 0, SHF_ALLOC);
   Out::ElfHeader->Size = sizeof(typename ELFT::Ehdr);
 
+  // Create wrapped symbols for -wrap option.
+  std::vector<WrappedSymbol> Wrapped = addWrappedSymbols<ELFT>(Args);
+
   // We need to create some reserved symbols such as _end. Create them.
   if (!Config->Relocatable)
     addReservedSymbols();
 
   // Apply version scripts.
   //
   // For a relocatable output, version scripts don't make sense, and
   // parsing a symbol version string (e.g. dropping "@ver1" from a symbol
   // name "foo@ver1") rather do harm, so we don't call this if -r is given.
   if (!Config->Relocatable)
     Symtab->scanVersionScript();
 
-  // Create wrapped symbols for -wrap option.
-  std::vector<WrappedSymbol> Wrapped = addWrappedSymbols<ELFT>(Args);
-
   // Do link-time optimization if given files are LLVM bitcode files.
   // This compiles bitcode files into real object files.
   //
   // With this the symbol table should be complete. After this, no new names
   // except a few linker-synthesized ones will be added to the symbol table.
   Symtab->addCombinedLTOObject<ELFT>();
   if (errorCount())
     return;

lld/trunk/test/ELF/Inputs/wrap-with-archive.s

+.global __executable_start
+.global __wrap_get_executable_start
+
+__wrap_get_executable_start:  
+  movabs $__executable_start,%rdx

lld/trunk/test/ELF/wrap-with-archive.s

+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/wrap-with-archive.s -o %t2
+// RUN: llvm-ar rcs %t3 %t2
+// RUN: ld.lld -o %t4 %t %t3 -wrap get_executable_start
+
+// Regression test for https://bugs.llvm.org/show_bug.cgi?id=40134
+  
+.global get_executable_start
+.global _start
+
+_start:
+  jmp get_executable_start