[ELF] - Implement --push-state/--pop-state.

[grimar]

Summary

This is PR34567 ("Bug 34567 - lld: unknown argument: --push-state, --pop-state on ubuntu when using asan")

Documentation (https://sourceware.org/binutils/docs/ld/Options.html) specifies these options as:

--push-state
The --push-state allows to preserve the current state of the flags which govern the input file handling so that they can all be restored with one corresponding --pop-state option.
The option which are covered are: -Bdynamic, -Bstatic, -dn, -dy, -call_shared, -non_shared, -static, -N, -n, --whole-archive, --no-whole-archive, -r, -Ur, --copy-dt-needed-entries, --no-copy-dt-needed-entries, --as-needed, --no-as-needed, and -a.
--pop-state
Undoes the effect of –push-state, restores the previous values of the flags governing input file handling.

gold implementation was: https://sourceware.org/bugzilla/show_bug.cgi?id=18989.

Unlike said in specification, gold preserves only position-dependent options. And that behavior looks correct for me,
I do not see any reasons to preserve/restore position-independent options. Also gold implements real stack with nesting to any depth.
I do not think we really need to do that, at least until bfd does not supports the same.
This patch implements probably simplest way I can imagine.

[ruiu]

I think I don't really like this option. This seems too hairy feature to me. I believe it shouldn't have been added to the linker in the first place.

[grimar]

In D37733#868245, @ruiu wrote:

I think I don't really like this option. This seems too hairy feature to me. I believe it shouldn't have been added to the linker in the first place.

Its wierd feature indeed. It was reported (https://stackoverflow.com/questions/37603238/fsanitize-not-using-gold-linker-in-gcc-6-1) that -fuse-ld=gold
could be a workaround previously for use of gcc -fsanitize. But now gold also supports it and I wonder what would be the correct behavior for LLD.
If we don't support it them most likely will fail, though feature itself and its description looks not worked out well for me.
I think we can put this on hold for now and watch.

[predelnik]

Well making a link to lld as ld.gold doesn't work as a workaround anyway. Looks like the only "workaround" is to use clang instead of gcc since these options are added by gcc on ubuntu for some obscure reason.

[grimar]

Abandoning until will be decided LLD wants to support it.

ELF/Driver.cpp

static bool getBinaryOption(StringRef S) {
   if (S == "elf" || S == "default")
     return false;
   error("unknown -format value: " + S +
         " (supported formats: elf, default, binary)");
   return false;
 }
 
 void LinkerDriver::createFiles(opt::InputArgList &Args) {
+  std::vector<std::pair<bool *, bool>> State = {
+      {&Config->AsNeeded, Config->AsNeeded},
+      {&Config->Static, Config->Static},
+      {&InBinary, InBinary},
+      {&InWholeArchive, InWholeArchive}};
+
   for (auto *Arg : Args) {
     switch (Arg->getOption().getUnaliasedOption().getID()) {
     case OPT_library:
       addLibrary(Arg->getValue());
       break;
     case OPT_INPUT:
       addFile(Arg->getValue(), /*WithLOption=*/false);
       break;
case OPT_no_whole_archive:
       InWholeArchive = false;
       break;
     case OPT_start_lib:
       InLib = true;
       break;
     case OPT_end_lib:
       InLib = false;
       break;
+    case OPT_pop_state:
+      for (std::pair<bool *, bool> &P : State)
+        *P.first = P.second;
+      break;
+    case OPT_push_state:
+      for (std::pair<bool *, bool> &P : State)
+        P.second = *P.first;
+      break;
     }
   }
 
   if (Files.empty() && ErrorCount == 0)
     error("no input files");
 }
 
 // If -m <machine_type> was not given, infer it from object files.

ELF/Options.td

 def oformat: Separate<["--"], "oformat">, MetaVarName<"<format>">,
   HelpText<"Specify the binary format for the output object file">;
 
 def omagic: Flag<["--"], "omagic">, MetaVarName<"<magic>">,
   HelpText<"Set the text and data sections to be readable and writable">;
 
 def pie: F<"pie">, HelpText<"Create a position independent executable">;
 
+def pop_state: Flag<["--"], "pop-state">,
+  HelpText<"Restore position dependent options">;
+
 def print_gc_sections: F<"print-gc-sections">,
   HelpText<"List removed unused sections">;
 
 def print_map: F<"print-map">,
   HelpText<"Print a link map to the standard output">;
 
+def push_state: Flag<["--"], "push-state">,
+  HelpText<"Preserve position dependent options">;
+
 defm reproduce: Eq<"reproduce">,
   HelpText<"Dump linker invocation and input files for debugging">;
 
 defm rpath: Eq<"rpath">, HelpText<"Add a DT_RUNPATH to the output">;
 
 def relocatable: F<"relocatable">, HelpText<"Create relocatable object file">;
 
 defm retain_symbols_file: Eq<"retain-symbols-file">,

test/ELF/as-needed.s

 // RUN: llvm-readobj -dynamic-table %t2 | FileCheck %s
 
 // RUN: ld.lld --as-needed %t.o %t2.so %t3.so %t4.so -o %t2
 // RUN: llvm-readobj -dynamic-table %t2 | FileCheck -check-prefix=CHECK2 %s
 
 // RUN: ld.lld --as-needed %t.o %t2.so --no-as-needed %t3.so %t4.so -o %t2
 // RUN: llvm-readobj -dynamic-table %t2 | FileCheck %s
 
+// RUN: ld.lld --push-state --as-needed %t.o %t2.so --pop-state %t3.so %t4.so -o %t2
+// RUN: llvm-readobj -dynamic-table %t2 | FileCheck %s
+
 /// GROUP directive is the same as --as-needed.
 
 // RUN: echo "GROUP(\"%t2.so\" \"%t3.so\" \"%t4.so\")" > %t.script
 // RUN: ld.lld %t.o %t.script -o %t2
 // RUN: llvm-readobj -dynamic-table %t2 | FileCheck %s
 
 // RUN: echo "GROUP(AS_NEEDED(\"%t2.so\" \"%t3.so\" \"%t4.so\"))" > %t.script
 // RUN: ld.lld %t.o %t.script -o %t2

test/ELF/format-binary.test

 # REQUIRES: x86
 
 # RUN: echo -n "Fluffle Puff" > %t.binary
 # RUN: ld.lld -m elf_x86_64 -r -b binary %t.binary -o %t.out
 # RUN: llvm-readobj %t.out -sections -section-data -symbols | FileCheck %s
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 # RUN: ld.lld %t.o -b binary %t.binary -b default %t.o -shared -o %t.out
 
+## Check --push-state/--pop-state works with -b.
+# RUN: ld.lld %t.o --push-state -b binary %t.binary --pop-state %t.o -shared -o %t.out
+
 # RUN: not ld.lld -b foo > %t.log 2>&1
 # RUN: FileCheck -check-prefix=ERR %s < %t.log
 # ERR: error: unknown -format value: foo (supported formats: elf, default, binary)
 
 # CHECK:          Name: .data
 # CHECK-NEXT:     Type: SHT_PROGBITS
 # CHECK-NEXT:     Flags [
 # CHECK-NEXT:       SHF_ALLOC

test/ELF/libsearch.s

 
 // Should not search for dynamic libraries if -Bstatic is specified
 // RUN: ld.lld -o %t3 %t.o -L%t.dir -Bstatic -lls
 // RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=STATIC %s
 // RUN: not ld.lld -o %t3 %t.o -L%t.dir -Bstatic -lls2 2>&1 \
 // RUN:   | FileCheck --check-prefix=NOLIB2 %s
 // NOLIB2: unable to find library -lls2
 
+// Check --pop-state/--push-state work for -Bstatic/-Bdynamic.
+// RUN: ld.lld -Bstatic --push-state -Bdynamic -o %t3 %t.o -L%t.dir --pop-state -lls
+// RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=STATIC %s
+// RUN: not ld.lld -o %t3 %t.o -L%t.dir -Bstatic -lls2 2>&1 \
+// RUN:   | FileCheck --check-prefix=NOLIB2 %s
+
 // -Bdynamic should restore default behaviour
 // RUN: ld.lld -o %t3 %t.o -L%t.dir -Bstatic -Bdynamic -lls
 // RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=DYNAMIC %s
 
 // -Bstatic and -Bdynamic should affect only libraries which follow them
 // RUN: ld.lld -o %t3 %t.o -L%t.dir -lls -Bstatic -Bdynamic
 // RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=DYNAMIC %s
 // RUN: ld.lld -o %t3 %t.o -L%t.dir -Bstatic -lls -Bdynamic

test/ELF/whole-archive.s

 // ADDED: Symbols [
 // ADDED: Name: _bar
 // ADDED: ]
 
 // --no-whole-archive should restore default behaviour
 // RUN: ld.lld -o %t3 %t.o --whole-archive --no-whole-archive %t.a
 // RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=NOTADDED %s
 
+// Check --push-state/--pop-state works for --whole-archive.
+// RUN: ld.lld -o %t3 %t.o --push-state --whole-archive --pop-state %t.a
+// RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=NOTADDED %s
+
 // --whole-archive and --no-whole-archive should affect only archives which follow them
 // RUN: ld.lld -o %t3 %t.o %t.a --whole-archive --no-whole-archive
 // RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=NOTADDED %s
 // RUN: ld.lld -o %t3 %t.o --whole-archive %t.a --no-whole-archive
 // RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=ADDED %s
 
 // --whole-archive should also work with thin archives
 // RUN: rm -f %tthin.a
 // RUN: llvm-ar --format=gnu rcsT %tthin.a %ta.o
 // RUN: ld.lld -o %t3 %t.o --whole-archive %tthin.a
 // RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=ADDED %s
 
 .globl _start
 _start: