[llvm-config] Print --system-libs only when static linking

[mgorny]

Summary

Modify the --system-libs option in llvm-config to print system libs only
when using static linking. The system libraries are irrelevant when
linking to a shared library since the library has appropriate library
dependencies embedded.

Modify the --system-libs test appropriately to force static linking, and
disable it if static libs are not available (i.e. BUILD_SHARED_LIBS is
enabled).

[compnerd]

tools/llvm-config/llvm-config.cpp

700

The braces are unnecessary. You can probably even just use a ternary.

OS << (LinkMode == LinkModeShared ? "" : LLVM_SYSTEM_LIBS) << '\n';

[mgorny]

tools/llvm-config/llvm-config.cpp

700

Yeah, that makes sense.

[mgorny]

I've left the outer quotes because of the comment inside.

[mgorny]

s/quotes/braces/.

[mgorny]

A gentle ping.

[mgorny]

@compnerd, ping.

[mgorny]

Rebased on top of the cmake->lit argument refactor.

[compnerd]

You can house the comment above the conditional and remove the braces.

test/CMakeLists.txt

 if(LLVM_BUILD_EXAMPLES)
   set(ENABLE_EXAMPLES 1)
 endif()
 
+# Convert 1 for easy processing in Python.
+if(BUILD_SHARED_LIBS)
+  set(BUILD_SHARED_LIBS 1)
+endif()
+
 configure_lit_site_cfg(
   ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.in
   ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg
   )
 configure_lit_site_cfg(
   ${CMAKE_CURRENT_SOURCE_DIR}/Unit/lit.site.cfg.in
   ${CMAKE_CURRENT_BINARY_DIR}/Unit/lit.site.cfg
   )

test/lit.cfg

 if sys.platform in ['win32', 'cygwin']:
     loadable_module = (config.enable_shared == 1)
 else:
     loadable_module = True
 
 if loadable_module:
     config.available_features.add('loadable_module')
 
+# Static libraries are not built if BUILD_SHARED_LIBS is ON.
+if config.build_shared_libs != '1':
+    config.available_features.add("static-libs")
+
 # Sanitizers.
 if 'Address' in config.llvm_use_sanitizer:
     config.available_features.add("asan")
 else:
     config.available_features.add("not_asan")
 if 'Memory' in config.llvm_use_sanitizer:
     config.available_features.add("msan")
 else:

test/lit.site.cfg.in

 config.host_ldflags = "@HOST_LDFLAGS@"
 config.llvm_use_intel_jitevents = "@LLVM_USE_INTEL_JITEVENTS@"
 config.llvm_use_sanitizer = "@LLVM_USE_SANITIZER@"
 config.have_zlib = "@HAVE_LIBZ@"
 config.have_libxar = "@HAVE_LIBXAR@"
 config.have_dia_sdk = @HAVE_DIA_SDK@
 config.enable_ffi = "@LLVM_ENABLE_FFI@"
 config.test_examples = "@ENABLE_EXAMPLES@"
+config.build_shared_libs = "@BUILD_SHARED_LIBS@"
 
 # Support substitution of the tools_dir with user parameters. This is
 # used when we can't determine the tool dir at configuration time.
 try:
     config.llvm_tools_dir = config.llvm_tools_dir % lit_config.params
     config.llvm_shlib_dir = config.llvm_shlib_dir % lit_config.params
 except KeyError:
     e = sys.exc_info()[1]
     key, = e.args
     lit_config.fatal("unable to find %r parameter, use '--param=%s=VALUE'" % (key,key))
 
 # Let the main config do the real work.
 lit_config.load_config(config, "@LLVM_SOURCE_DIR@/test/lit.cfg")

test/tools/llvm-config/system-libs.test

-RUN: llvm-config --system-libs 2>&1 | FileCheck %s
+RUN: llvm-config --link-static --system-libs 2>&1 | FileCheck %s
+REQUIRES: static-libs
 UNSUPPORTED: system-windows
 CHECK: -l
 CHECK-NOT: error
 CHECK-NOT: warning

test/tools/llvm-config/system-libs.windows.test

-RUN: llvm-config --system-libs 2>&1 | FileCheck %s
+RUN: llvm-config --link-static --system-libs 2>&1 | FileCheck %s
+REQUIRES: static-libs
 REQUIRES: system-windows
 CHECK-NOT: -l
 CHECK: psapi.lib shell32.lib ole32.lib uuid.lib
 CHECK-NOT: error
 CHECK-NOT: warning

tools/llvm-config/llvm-config.cpp

if (PrintLibs || PrintLibNames || PrintLibFiles) {
           PrintForLib(Lib);
         }
       }
       OS << '\n';
     }
 
     // Print SYSTEM_LIBS after --libs.
     // FIXME: Each LLVM component may have its dependent system libs.
-    if (PrintSystemLibs)
+    if (PrintSystemLibs) {
+      // Output empty system libraries if linking against a shared library
+      // (since the library links to all system libs already)
+      if (LinkMode == LinkModeShared) {
+        OS << '\n';
+      } else {
         OS << LLVM_SYSTEM_LIBS << '\n';
+      }
+    }
   } else if (!Components.empty()) {
     errs() << "llvm-config: error: components given, but unused\n\n";
     usage();
   }
 
   return 0;
 }