[PATCH] D127528: [Clang] Let the linker choose shared or static libunwind unless specified

[Petr Hosek via Phabricator via cfe-commits]

phosek created this revision.
phosek added reviewers: saugustine, jkz.
Herald added a subscriber: mstorsjo.
Herald added a project: All.
phosek requested review of this revision.
Herald added subscribers: cfe-commits, MaskRay.
Herald added a project: clang.

We shouldn't assume that libunwind.so is available. Rather can defer
the decision to the linker which defaults to libunwind.so, but if .so
isn't available, it'd pick libunwind.a. Users can use -static-libgcc
and -shared-libgcc to override this behavior and explicitly choose
the version they want.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D127528

Files:
  clang/lib/Driver/ToolChains/CommonArgs.cpp
  clang/test/Driver/compiler-rt-unwind.c


Index: clang/test/Driver/compiler-rt-unwind.c
===================================================================
--- clang/test/Driver/compiler-rt-unwind.c
+++ clang/test/Driver/compiler-rt-unwind.c
@@ -13,7 +13,15 @@
 // RUN:     --gcc-toolchain="" -resource-dir=%S/Inputs/resource_dir \
 // RUN:   | FileCheck --check-prefix=RTLIB-GCC-UNWINDLIB-COMPILER-RT %s
 // RTLIB-GCC-UNWINDLIB-COMPILER-RT: "{{.*}}lgcc"
-// RTLIB-GCC-UNWINDLIB-COMPILER-RT: "{{.*}}l:libunwind.so"
+// RTLIB-GCC-UNWINDLIB-COMPILER-RT: "{{.*}}lunwind"
+//
+// RUN: %clang -### %s 2>&1 \
+// RUN:     --target=x86_64-unknown-linux -rtlib=libgcc --unwindlib=libunwind \
+// RUN:     -shared-libgcc \
+// RUN:     --gcc-toolchain="" -resource-dir=%S/Inputs/resource_dir \
+// RUN:   | FileCheck --check-prefix=RTLIB-GCC-SHARED-UNWINDLIB-COMPILER-RT %s
+// RTLIB-GCC-SHARED-UNWINDLIB-COMPILER-RT: "{{.*}}l:libunwind.so"
+// RTLIB-GCC-SHARED-UNWINDLIB-COMPILER-RT: "{{.*}}lgcc"
 //
 // RUN: %clang -### %s 2>&1 \
 // RUN:     --target=x86_64-unknown-linux -rtlib=libgcc --unwindlib=libunwind \
Index: clang/lib/Driver/ToolChains/CommonArgs.cpp
===================================================================
--- clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -1471,17 +1471,12 @@
 static LibGccType getLibGccType(const ToolChain &TC, const Driver &D,
                                 const ArgList &Args) {
   if (Args.hasArg(options::OPT_static_libgcc) ||
-      Args.hasArg(options::OPT_static) || Args.hasArg(options::OPT_static_pie))
+      Args.hasArg(options::OPT_static) || Args.hasArg(options::OPT_static_pie) ||
+      // The Android NDK only provides libunwind.a, not libunwind.so.
+      TC.getTriple().isAndroid())
     return LibGccType::StaticLibGcc;
   if (Args.hasArg(options::OPT_shared_libgcc))
     return LibGccType::SharedLibGcc;
-  // The Android NDK only provides libunwind.a, not libunwind.so.
-  if (TC.getTriple().isAndroid())
-    return LibGccType::StaticLibGcc;
-  // For MinGW, don't imply a shared libgcc here, we only want to return
-  // SharedLibGcc if that was explicitly requested.
-  if (D.CCCIsCXX() && !TC.getTriple().isOSCygMing())
-    return LibGccType::SharedLibGcc;
   return LibGccType::UnspecifiedLibGcc;
 }
 
@@ -1508,7 +1503,7 @@
     return;
 
   LibGccType LGT = getLibGccType(TC, D, Args);
-  bool AsNeeded = LGT == LibGccType::UnspecifiedLibGcc &&
+  bool AsNeeded = LGT == LibGccType::UnspecifiedLibGcc && !D.CCCIsCXX() &&
                   !TC.getTriple().isAndroid() &&
                   !TC.getTriple().isOSCygMing() && !TC.getTriple().isOSAIX();
   if (AsNeeded)
@@ -1532,15 +1527,15 @@
         CmdArgs.push_back("-lunwind");
     } else if (LGT == LibGccType::StaticLibGcc) {
       CmdArgs.push_back("-l:libunwind.a");
-    } else if (TC.getTriple().isOSCygMing()) {
-      if (LGT == LibGccType::SharedLibGcc)
+    } else if (LGT == LibGccType::SharedLibGcc) {
+      if (TC.getTriple().isOSCygMing())
         CmdArgs.push_back("-l:libunwind.dll.a");
       else
-        // Let the linker choose between libunwind.dll.a and libunwind.a
-        // depending on what's available, and depending on the -static flag
-        CmdArgs.push_back("-lunwind");
+        CmdArgs.push_back("-l:libunwind.so");
     } else {
-      CmdArgs.push_back("-l:libunwind.so");
+      // Let the linker choose between libunwind.so and libunwind.a
+      // depending on what's available, and depending on the -static flag
+      CmdArgs.push_back("-lunwind");
     }
     break;
   }
@@ -1552,10 +1547,12 @@
 static void AddLibgcc(const ToolChain &TC, const Driver &D,
                       ArgStringList &CmdArgs, const ArgList &Args) {
   LibGccType LGT = getLibGccType(TC, D, Args);
-  if (LGT != LibGccType::SharedLibGcc)
+  if (LGT == LibGccType::StaticLibGcc ||
+      (LGT == LibGccType::UnspecifiedLibGcc && !D.CCCIsCXX()))
     CmdArgs.push_back("-lgcc");
   AddUnwindLibrary(TC, D, CmdArgs, Args);
-  if (LGT == LibGccType::SharedLibGcc)
+  if (LGT == LibGccType::SharedLibGcc ||
+      (LGT == LibGccType::UnspecifiedLibGcc && D.CCCIsCXX()))
     CmdArgs.push_back("-lgcc");
 }
 


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