From 67013ee5feecca0c1e1dd8a149b20779a9b6c12a Mon Sep 17 00:00:00 2001

From: serge-sans-paille <sguelton@redhat.com>

Date: Wed, 23 Sep 2020 12:47:30 +0000

Subject: [PATCH] Driver: Prefer gcc toolchains with libgcc_s.so when not

 static linking libgcc

Fedora ships cross-compilers on all platforms, so a user could end up

with a gcc x86_64 cross-compiler installed on an x86_64 system. clang

maintains a list of supported triples for each target and when all

else is equal will prefer toolchains with triples that appear earlier

in the list.

The cross-compiler triple on Fedora is x86_64-linux-gnu and this comes

before the Fedora system compiler's triple: x86_64-redhat-linux in

the triples list, so the cross compiler is always preferred. This

is a problem, because the cross compiler is missing libraries, like

libgcc_s.so, that clang expects to be there so linker invocations

will fail.

This patch fixes this by checking for the existence of libgcc_s.so

when it is required and taking that into account when selecting a

toolchain.

---

 lib/Driver/ToolChains/Gnu.cpp                    | 16 ++++++++++++++--

 lib/Driver/ToolChains/Gnu.h                      |  4 +++-

 .../usr/lib/gcc/x86_64-linux-gnu/7/crtbegin.o    |  0

 .../usr/lib/gcc/x86_64-redhat-linux/7/crtbegin.o |  0

 .../lib/gcc/x86_64-redhat-linux/7/libgcc_s.so    |  0

 test/Driver/linux-ld.c                           | 12 ++++++++++++

 6 files changed, 29 insertions(+), 3 deletions(-)

 create mode 100644 test/Driver/Inputs/fedora_28_tree/usr/lib/gcc/x86_64-linux-gnu/7/crtbegin.o

 create mode 100644 test/Driver/Inputs/fedora_28_tree/usr/lib/gcc/x86_64-redhat-linux/7/crtbegin.o

 create mode 100644 test/Driver/Inputs/fedora_28_tree/usr/lib/gcc/x86_64-redhat-linux/7/libgcc_s.so

diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp

index c8a7fce0..f28792b7 100644

--- a/clang/lib/Driver/ToolChains/Gnu.cpp

+++ b/clang/lib/Driver/ToolChains/Gnu.cpp

@@ -2500,6 +2500,8 @@ void Generic_GCC::GCCInstallationDetector::ScanLibDirForGCCTriple(

        (TargetArch == llvm::Triple::x86 &&

         TargetTriple.getOS() != llvm::Triple::Solaris)}};

+  bool NeedLibgccShared = !Args.hasArg(options::OPT_static_libgcc) &&

+                          !Args.hasArg(options::OPT_static);

   for (auto &Suffix : Suffixes) {

     if (!Suffix.Active)

       continue;

@@ -2517,8 +2519,17 @@ void Generic_GCC::GCCInstallationDetector::ScanLibDirForGCCTriple(

           continue; // Saw this path before; no need to look at it again.

       if (CandidateVersion.isOlderThan(4, 1, 1))

         continue;

-      if (CandidateVersion <= Version)

-        continue;

+

+      bool CandidateHasLibGccShared = false;

+      if (CandidateVersion <= Version) {

+        if (NeedLibgccShared && !HasLibGccShared) {

+          CandidateHasLibGccShared =

+                D.getVFS().exists(LI->path() + "/libgcc_s.so");

+

+        }

+        if (HasLibGccShared || !CandidateHasLibGccShared)

+          continue;

+      }

       if (!ScanGCCForMultilibs(TargetTriple, Args, LI->path(),

                                NeedsBiarchSuffix))

@@ -2532,6 +2543,7 @@ void Generic_GCC::GCCInstallationDetector::ScanLibDirForGCCTriple(

       GCCInstallPath = (LibDir + "/" + LibSuffix + "/" + VersionText).str();

       GCCParentLibPath = (GCCInstallPath + "/../" + Suffix.ReversePath).str();

       IsValid = true;

+      HasLibGccShared = CandidateHasLibGccShared;

     }

   }

 }

diff --git a/clang/lib/Driver/ToolChains/Gnu.h b/clang/lib/Driver/ToolChains/Gnu.h

index 52690ab4..2a4452d9 100644

--- a/clang/lib/Driver/ToolChains/Gnu.h

+++ b/clang/lib/Driver/ToolChains/Gnu.h

@@ -190,6 +190,7 @@ public:

   /// Driver, and has logic for fuzzing that where appropriate.

   class GCCInstallationDetector {

     bool IsValid;

+    bool HasLibGccShared;

     llvm::Triple GCCTriple;

     const Driver &D;

@@ -213,7 +214,8 @@ public:

     MultilibSet Multilibs;

   public:

-    explicit GCCInstallationDetector(const Driver &D) : IsValid(false), D(D) {}

+    explicit GCCInstallationDetector(const Driver &D)

+        : IsValid(false), HasLibGccShared(false), D(D) {}

     void init(const llvm::Triple &TargetTriple, const llvm::opt::ArgList &Args,

               ArrayRef<std::string> ExtraTripleAliases = None);

diff --git a/clang/test/Driver/Inputs/fedora_28_tree/usr/lib/gcc/x86_64-linux-gnu/7/crtbegin.o b/clang/test/Driver/Inputs/fedora_28_tree/usr/lib/gcc/x86_64-linux-gnu/7/crtbegin.o

new file mode 100644

index 00000000..e69de29b

diff --git a/clang/test/Driver/Inputs/fedora_28_tree/usr/lib/gcc/x86_64-redhat-linux/7/crtbegin.o b/clang/test/Driver/Inputs/fedora_28_tree/usr/lib/gcc/x86_64-redhat-linux/7/crtbegin.o

new file mode 100644

index 00000000..e69de29b

diff --git a/clang/test/Driver/Inputs/fedora_28_tree/usr/lib/gcc/x86_64-redhat-linux/7/libgcc_s.so b/clang/test/Driver/Inputs/fedora_28_tree/usr/lib/gcc/x86_64-redhat-linux/7/libgcc_s.so

new file mode 100644

index 00000000..e69de29b

diff --git a/clang/test/Driver/linux-ld.c b/test/Driver/linux-ld.c

index ec539522..95725d5c 100644

--- a/clang/test/Driver/linux-ld.c

+++ b/clang/test/Driver/linux-ld.c

@@ -784,6 +784,18 @@

 // CHECK-FEDORA-31-RISCV64: "{{.*}}/usr/lib/gcc/riscv64-redhat-linux/9{{/|\\\\}}crtend.o"

 // CHECK-FEDORA-31-RISCV64: "{{.*}}/usr/lib/gcc/riscv64-redhat-linux/9{{/|\\\\}}crtn.o"

 //

+// Check that clang does not select the cross compiler by default on Fedora 28.

+//

+// RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \

+// RUN:     --target=x86_64-unknown-linux-gnu \

+// RUN:     --gcc-toolchain="" \

+// RUN:     --sysroot=%S/Inputs/fedora_28_tree \

+// RUN:   | FileCheck --check-prefix=CHECK-FEDORA-28-X86_64 %s

+//

+// CHECK-FEDORA-28-X86_64: "{{.*}}ld{{(.exe)?}}" "--sysroot=[[SYSROOT:[^"]+]]"

+// CHECK-FEDORA-28-X86_64: "[[SYSROOT]]/usr/lib/gcc/x86_64-redhat-linux/7/crtbegin.o"

+// CHECK-FEDORA-28-X86_64: "-L[[SYSROOT]]/usr/lib/gcc/x86_64-redhat-linux/7"

+//

 // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \

 // RUN:     --target=arm-unknown-linux-gnueabi -rtlib=platform \

 // RUN:     --gcc-toolchain="" \

-- 

2.25.2