[Driver][Fuchsia] Avoid "argument unused" warnings (llvm#118416)

There should not be an error or warning reported for using
redundant options to control what goes into the link.  For
example, -nolibc -nostdlib.

Author: frobtech

clang/lib/Driver/ToolChains/Fuchsia.cpp

@@ -156,15 +156,19 @@ void fuchsia::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   addLinkerCompressDebugSectionsOption(ToolChain, Args, CmdArgs);
   AddLinkerInputs(ToolChain, Inputs, Args, CmdArgs, JA);
 
+  // Sample these options first so they are claimed even under -nostdlib et al.
+  bool NoLibc = Args.hasArg(options::OPT_nolibc);
+  bool OnlyLibstdcxxStatic = Args.hasArg(options::OPT_static_libstdcxx) &&
+                             !Args.hasArg(options::OPT_static);
+  bool Pthreads = Args.hasArg(options::OPT_pthread, options::OPT_pthreads);
+  bool SplitStack = Args.hasArg(options::OPT_fsplit_stack);
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs,
                    options::OPT_r)) {
     if (Args.hasArg(options::OPT_static))
       CmdArgs.push_back("-Bdynamic");
 
     if (D.CCCIsCXX()) {
       if (ToolChain.ShouldLinkCXXStdlib(Args)) {
-        bool OnlyLibstdcxxStatic = Args.hasArg(options::OPT_static_libstdcxx) &&
-                                   !Args.hasArg(options::OPT_static);
         CmdArgs.push_back("--push-state");
         CmdArgs.push_back("--as-needed");
         if (OnlyLibstdcxxStatic)
@@ -188,14 +192,13 @@ void fuchsia::Linker::ConstructJob(Compilation &C, const JobAction &JA,
 
     AddRunTimeLibs(ToolChain, D, CmdArgs, Args);
 
-    if (Args.hasArg(options::OPT_pthread) ||
-        Args.hasArg(options::OPT_pthreads))
+    if (Pthreads)
       CmdArgs.push_back("-lpthread");
 
-    if (Args.hasArg(options::OPT_fsplit_stack))
+    if (SplitStack)
       CmdArgs.push_back("--wrap=pthread_create");
 
-    if (!Args.hasArg(options::OPT_nolibc))
+    if (!NoLibc)
       CmdArgs.push_back("-lc");
   }
 
@@ -229,7 +232,7 @@ void fuchsia::StaticLibTool::ConstructJob(Compilation &C, const JobAction &JA,
 
   for (const auto &II : Inputs) {
     if (II.isFilename()) {
-       CmdArgs.push_back(II.getFilename());
+      CmdArgs.push_back(II.getFilename());
     }
   }
 
@@ -343,16 +346,14 @@ std::string Fuchsia::ComputeEffectiveClangTriple(const ArgList &Args,
   return Triple.str();
 }
 
-Tool *Fuchsia::buildLinker() const {
-  return new tools::fuchsia::Linker(*this);
-}
+Tool *Fuchsia::buildLinker() const { return new tools::fuchsia::Linker(*this); }
 
 Tool *Fuchsia::buildStaticLibTool() const {
   return new tools::fuchsia::StaticLibTool(*this);
 }
 
-ToolChain::RuntimeLibType Fuchsia::GetRuntimeLibType(
-    const ArgList &Args) const {
+ToolChain::RuntimeLibType
+Fuchsia::GetRuntimeLibType(const ArgList &Args) const {
   if (Arg *A = Args.getLastArg(clang::driver::options::OPT_rtlib_EQ)) {
     StringRef Value = A->getValue();
     if (Value != "compiler-rt")
@@ -363,13 +364,12 @@ ToolChain::RuntimeLibType Fuchsia::GetRuntimeLibType(
   return ToolChain::RLT_CompilerRT;
 }
 
-ToolChain::CXXStdlibType
-Fuchsia::GetCXXStdlibType(const ArgList &Args) const {
+ToolChain::CXXStdlibType Fuchsia::GetCXXStdlibType(const ArgList &Args) const {
   if (Arg *A = Args.getLastArg(options::OPT_stdlib_EQ)) {
     StringRef Value = A->getValue();
     if (Value != "libc++")
       getDriver().Diag(diag::err_drv_invalid_stdlib_name)
-        << A->getAsString(Args);
+          << A->getAsString(Args);
   }
 
   return ToolChain::CST_Libcxx;

clang/test/Driver/fuchsia.c

@@ -297,3 +297,9 @@
 // RUN: %clang --target=riscv64-unknown-fuchsia -mno-relax -### %s 2>&1 \
 // RUN:   | FileCheck -check-prefix=RISCV64-FLAGS %s
 // RISCV64-FLAGS: "-X" "--no-relax"
+
+// RUN: %clang -### %s --target=x86_64-unknown-fuchsia 2>&1 \
+// RUN:     -nostdlib -nolibc \
+// RUN:     | FileCheck %s -check-prefix=CHECK-NOSTDLIB-NOLIBC
+// CHECK-NOSTDLIB-NOLIBC-NOT: "warning:"
+// CHECK-NOSTDLIB-NOLIBC-NOT: "error:"