Make `llvm-config` detect whether or not LLVM is a shared library. If it is, then only try to link …

tools/llvm-config/llvm-config.cpp

 //===-- llvm-config.cpp - LLVM project configuration utility --------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This tool encapsulates information about an LLVM project configuration for
@@ skipping 331 matching lines @@
     // If no components were specified, default to "all".
     if (Components.empty())
       Components.push_back("all");
 
     // Construct the list of all the required libraries.
     std::vector<StringRef> RequiredLibs;
     ComputeLibsForComponents(Components, RequiredLibs,
                              /*IncludeNonInstalled=*/IsInDevelopmentTree);
 
     if (PrintLibs || PrintLibNames || PrintLibFiles) {
+      // If LLVM was built as a shared library, there will be only one thing
+      // that users should link against.
+      const bool IsSharedLib = (std::strcmp(BUILD_SHARED_LIBS, "ON") == 0);

[JF, 2015/06/24 21:09:01]

Could you change BUILD_SHARED_LIBS's name? There's a similarly-named variable in
cmake.

[Richard Diamond, 2015/06/24 21:44:30]

`BUILD_SHARED_LIBS` is the CMake var name. Or did you want me to change the name
to something that's not a CMake var name?

[JF, 2015/06/24 21:52:42]

If it's named the same as cmake's but doesn't have anything to do with it then
it'll be pretty confusing, so it should have a different name.

[Richard Diamond, 2015/06/24 21:54:48]

Setting `BUILD_SHARED_LIBS` to `ON` tells LLVM to build shared libraries, so
it's apropos.

+      if (IsSharedLib) {
+        RequiredLibs.clear();
+        RequiredLibs.push_back("libLLVM-" PACKAGE_VERSION ".so");

[JF, 2015/06/24 21:09:01]

Here and on line 375 you hard-code ".so". That seems fine since the code already
hard-codes ".a", but you should add ".dylib" for Mac (I'm assuming that's what
LLVm is configured to generate).

+      }
+
       for (unsigned i = 0, e = RequiredLibs.size(); i != e; ++i) {
         StringRef Lib = RequiredLibs[i];
         if (i)
           OS << ' ';
 
         if (PrintLibNames) {
           OS << Lib;
         } else if (PrintLibFiles) {
           OS << ActiveLibDir << '/' << Lib;
         } else if (PrintLibs) {
           // If this is a typical library name, include it using -l.
-          if (Lib.startswith("lib") && Lib.endswith(".a")) {
-            OS << "-l" << Lib.slice(3, Lib.size()-2);
-            continue;
+          if (Lib.startswith("lib")) {
+            if (Lib.endswith(".a")) {
+              OS << "-l" << Lib.slice(3, Lib.size() - 2);
+              continue;
+            } else if (Lib.endswith(".so")) {

[JF, 2015/06/24 21:09:01]

Here too.

+              OS << "-l" << Lib.slice(3, Lib.size() - 3);
+              continue;
+            }
           }
 
           // Otherwise, print the full path.
           OS << ActiveLibDir << '/' << Lib;
         }
       }
       OS << '\n';
     }
 
     // Print SYSTEM_LIBS after --libs.
     // FIXME: Each LLVM component may have its dependent system libs.
     if (PrintSystemLibs)
       OS << LLVM_SYSTEM_LIBS << '\n';
   } else if (!Components.empty()) {
     errs() << "llvm-config: error: components given, but unused\n\n";
     usage();
   }
 
   return 0;
 }