Fix for #3374

driver/linker-gcc.cpp

@@ -556,7 +556,14 @@ void ArgsBuilder::build(llvm::StringRef outputPath,
     }
   }
 
-  addDefaultPlatformLibs();
+  const auto explicitPlatformLibs = getExplicitPlatformLibs();
+  if (explicitPlatformLibs.hasValue()) {
+    for (const auto &name : explicitPlatformLibs.getValue()) {
+      args.push_back("-l" + name);
+    }
+  } else {
+    addDefaultPlatformLibs();
+  }
 
   addTargetFlags();
 }

driver/linker-msvc.cpp

@@ -206,23 +206,24 @@ int linkObjToBinaryMSVC(llvm::StringRef outputPath,
     addSwitch(ls);
   }
 
-  // default platform libs
-  // TODO check which libaries are necessary
-  args.push_back("kernel32.lib");
-  args.push_back("user32.lib");
-  args.push_back("gdi32.lib");
-  args.push_back("winspool.lib");
-  args.push_back("shell32.lib"); // required for dmain2.d
-  args.push_back("ole32.lib");
-  args.push_back("oleaut32.lib");
-  args.push_back("uuid.lib");
-  args.push_back("comdlg32.lib");
-  args.push_back("advapi32.lib");
-
-  // these get pulled in by druntime (rt/msvc.c); include explicitly for
-  // -betterC convenience (issue #3035)
-  args.push_back("oldnames.lib");
-  args.push_back("legacy_stdio_definitions.lib");
+  auto explicitPlatformLibs = getExplicitPlatformLibs();
+  if (explicitPlatformLibs.hasValue()) {
+    for (auto &lib : explicitPlatformLibs.getValue()) {
+      args.push_back(llvm::sys::path::has_extension(lib) ? std::move(lib)
+                                                         : lib + ".lib");
+    }
+  } else {
+    // default platform libs
+    // TODO check which libaries are necessary
+    args.insert(args.end(),
+                {"kernel32.lib", "user32.lib", "gdi32.lib", "winspool.lib",
+                 "shell32.lib", // required for dmain2.d
+                 "ole32.lib", "oleaut32.lib", "uuid.lib", "comdlg32.lib",
+                 "advapi32.lib",
+                 // these get pulled in by druntime (rt/msvc.c); include
+                 // explicitly for -betterC convenience (issue #3035)
+                 "oldnames.lib", "legacy_stdio_definitions.lib"});
+  }
 
   Logger::println("Linking with: ");
   Stream logstr = Logger::cout();

driver/linker.cpp

@@ -32,6 +32,11 @@ static cl::opt<bool> linkInternally("link-internally", cl::ZeroOrMore,
 constexpr bool linkInternally = false;
 #endif
 
+static cl::opt<std::string> platformLib(
+    "platformlib", cl::ZeroOrMore, cl::value_desc("lib1,lib2,..."),
+    cl::desc("Platform libraries to link with (overrides previous)"),
+    cl::cat(opts::linkingCategory));
+
 static cl::opt<bool> noDefaultLib(
     "nodefaultlib", cl::ZeroOrMore, cl::Hidden,
     cl::desc("Don't add a default library for linking implicitly"));
@@ -136,6 +141,26 @@ static std::string getOutputName() {
 
 //////////////////////////////////////////////////////////////////////////////
 
+static std::vector<std::string>
+parseLibNames(llvm::StringRef commaSeparatedList, llvm::StringRef suffix = {}) {
+  std::vector<std::string> result;
+
+  std::stringstream list(commaSeparatedList);
+  while (list.good()) {
+    std::string lib;
+    std::getline(list, lib, ',');
+    if (lib.empty()) {
+      continue;
+    }
+
+    result.push_back(suffix.empty() ? std::move(lib) : (lib + suffix).str());
+  }
+
+  return result;
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
 static std::vector<std::string> getDefaultLibNames() {
   std::vector<std::string> result;
 
@@ -144,31 +169,35 @@ static std::vector<std::string> getDefaultLibNames() {
                        "overrides the existing list instead of appending to "
                        "it. Please use the latter instead.");
   } else if (!global.params.betterC) {
-    const bool addDebugSuffix =
-        (linkDefaultLibDebug && debugLib.getNumOccurrences() == 0);
-    const bool addSharedSuffix = linkAgainstSharedDefaultLibs();
-
-    // Parse comma-separated default library list.
-    std::stringstream libNames(
-        linkDefaultLibDebug && !addDebugSuffix ? debugLib : defaultLib);
-    while (libNames.good()) {
-      std::string lib;
-      std::getline(libNames, lib, ',');
-      if (lib.empty()) {
-        continue;
-      }
-
-      result.push_back((llvm::Twine(lib) + (addDebugSuffix ? "-debug" : "") +
-                        (addSharedSuffix ? "-shared" : ""))
-                           .str());
+    llvm::StringRef list = defaultLib;
+    std::string suffix;
+
+    if (linkDefaultLibDebug) {
+      if (debugLib.getNumOccurrences() == 0)
+        suffix = "-debug";
+      else
+        list = debugLib;
     }
+    if (linkAgainstSharedDefaultLibs()) {
+      suffix += "-shared";
+    }
+
+    result = parseLibNames(list, suffix);
   }
 
   return result;
 }
 
 //////////////////////////////////////////////////////////////////////////////
 
+llvm::Optional<std::vector<std::string>> getExplicitPlatformLibs() {
+  if (platformLib.getNumOccurrences() > 0)
+    return parseLibNames(platformLib);
+  return llvm::None;
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
 bool useInternalLLDForLinking() {
   return linkInternally
 #if LDC_WITH_LLD

driver/linker.h

@@ -39,6 +39,11 @@ llvm::cl::boolOrDefault linkFullyStatic();
  */
 bool linkAgainstSharedDefaultLibs();
 
+/**
+ * Returns the -platformlib library names, if specified.
+ */
+llvm::Optional<std::vector<std::string>> getExplicitPlatformLibs();
+
 /**
  * Returns the value of -mscrtlib.
  */

tests/linking/platformlib.d

@@ -0,0 +1,27 @@
+// Make sure -platformlib overrides the default platform libraries list.
+
+
+// RUN: %ldc %s -platformlib= -gcc=echo -linker=echo | FileCheck --check-prefix=EMPTY %s
+
+// EMPTY-NOT: -lrt
+// EMPTY-NOT: -ldl
+// EMPTY-NOT: -lpthread
+// EMPTY-NOT: -lm
+
+// EMPTY-NOT: kernel32
+// EMPTY-NOT: user32
+// EMPTY-NOT: gdi32
+// EMPTY-NOT: winspool
+// EMPTY-NOT: shell32
+// EMPTY-NOT: ole32
+// EMPTY-NOT: oleaut32
+// EMPTY-NOT: uuid
+// EMPTY-NOT: comdlg32
+// EMPTY-NOT: advapi32
+// EMPTY-NOT: oldnames
+// EMPTY-NOT: legacy_stdio_definitions
+
+
+// RUN: %ldc %s -platformlib=myPlatformLib1,myPlatformLib2 -gcc=echo -linker=echo | FileCheck --check-prefix=CUSTOM %s
+
+// CUSTOM: {{(-lmyPlatformLib1 -lmyPlatformLib2)|(myPlatformLib1.lib myPlatformLib2.lib)}}