Add options to specify linker tool

Offer the capability, through variable `CMAKE_LINKER_TYPE`, as well as
the target property `LINKER_TYPE` to specify which linker must be used.

The implementation of this capability is specified by variables specific
to the language and linker type: `CMAKE_<LANG>_USING_LINKER_<TYPE>`.
Some definitions are provided as part of `CMake`.

For example, to select the `LLVM` linker rather than the standard one,
the type `LLD` should be specified through the variable `CMAKE_LINKER_TYPE`.
And, on `Apple`, `Linux` and some environments on `Windows`, the variable
`CMAKE_<LANG>_USING_LINKER_LLD` has value `-fuse-ld=lld`. And for `Windows`
environments  based on `MSVC`, where the linker is used directly, the tool
`lld-link.exe` will be used rather than `link.exe`.

Fixes: #19174, #24254, #24990

1 files changed, 69 insertions, 0 deletions

diff --git a/Source/cmGeneratorTarget.cxx b/Source/cmGeneratorTarget.cxx
index 2ea18bd..f7a6a4e 100644
--- a/Source/cmGeneratorTarget.cxx
+++ b/Source/cmGeneratorTarget.cxx
@@ -868,6 +868,31 @@ cmValue cmGeneratorTarget::GetFeature(const std::string& feature,
   return this->LocalGenerator->GetFeature(feature, config);
 }
 
+std::string cmGeneratorTarget::GetLinkerTypeProperty(
+  std::string const& lang, std::string const& config) const
+{
+  std::string propName{ "LINKER_TYPE" };
+  auto linkerType = this->GetProperty(propName);
+  if (!linkerType.IsEmpty()) {
+    cmGeneratorExpressionDAGChecker dagChecker(this, propName, nullptr,
+                                               nullptr);
+    auto ltype =
+      cmGeneratorExpression::Evaluate(*linkerType, this->GetLocalGenerator(),
+                                      config, this, &dagChecker, this, lang);
+    if (this->IsDeviceLink()) {
+      cmList list{ ltype };
+      const auto DL_BEGIN = "<DEVICE_LINK>"_s;
+      const auto DL_END = "</DEVICE_LINK>"_s;
+      cm::erase_if(list, [&](const std::string& item) {
+        return item == DL_BEGIN || item == DL_END;
+      });
+      return list.to_string();
+    }
+    return ltype;
+  }
+  return std::string{};
+}
+
 const char* cmGeneratorTarget::GetLinkPIEProperty(
   const std::string& config) const
 {
@@ -5515,6 +5540,50 @@ std::string cmGeneratorTarget::GetLinkerLanguage(
   return this->GetLinkClosure(config)->LinkerLanguage;
 }
 
+std::string cmGeneratorTarget::GetLinkerTool(const std::string& config) const
+{
+  return this->GetLinkerTool(this->GetLinkerLanguage(config), config);
+}
+
+std::string cmGeneratorTarget::GetLinkerTool(const std::string& lang,
+                                             const std::string& config) const
+{
+  auto usingLinker =
+    cmStrCat("CMAKE_", lang, "_USING_", this->IsDeviceLink() ? "DEVICE_" : "",
+             "LINKER_");
+  auto format = this->Makefile->GetDefinition(cmStrCat(usingLinker, "MODE"));
+  if (!format || format != "TOOL"_s) {
+    return this->Makefile->GetDefinition("CMAKE_LINKER");
+  }
+
+  auto linkerType = this->GetLinkerTypeProperty(lang, config);
+  if (linkerType.empty()) {
+    linkerType = "DEFAULT";
+  }
+  usingLinker = cmStrCat(usingLinker, linkerType);
+  auto linkerTool = this->Makefile->GetDefinition(usingLinker);
+
+  if (!linkerTool) {
+    if (this->GetGlobalGenerator()->IsVisualStudio() &&
+        linkerType == "DEFAULT"_s) {
+      return std::string{};
+    }
+
+    // fall-back to generic definition
+    linkerTool = this->Makefile->GetDefinition("CMAKE_LINKER");
+
+    if (linkerType != "DEFAULT"_s) {
+      this->LocalGenerator->IssueMessage(
+        MessageType::FATAL_ERROR,
+        cmStrCat("LINKER_TYPE '", linkerType,
+                 "' is unknown. Did you forgot to define '", usingLinker,
+                 "' variable?"));
+    }
+  }
+
+  return linkerTool;
+}
+
 std::string cmGeneratorTarget::GetPDBOutputName(
   const std::string& config) const
 {