VS: Add CMAKE_GENERATOR_PLATFORM field to control Windows SDK selection

Add a `version=` field to explicitly control the SDK version selection
without relying on `CMAKE_SYSTEM_VERSION`.

Fixes: #16713

1 files changed, 69 insertions, 2 deletions

diff --git a/Source/cmGlobalVisualStudio14Generator.cxx b/Source/cmGlobalVisualStudio14Generator.cxx
index 87c8a5e..9ae80bb 100644
--- a/Source/cmGlobalVisualStudio14Generator.cxx
+++ b/Source/cmGlobalVisualStudio14Generator.cxx
@@ -142,7 +142,31 @@ bool cmGlobalVisualStudio14Generator::InitializePlatformWindows(cmMakefile* mf)
   if (cmHasLiteralPrefix(this->SystemVersion, "10.0")) {
     return this->SelectWindows10SDK(mf);
   }
-  return true;
+  return this->VerifyNoGeneratorPlatformVersion(mf);
+}
+
+bool cmGlobalVisualStudio14Generator::VerifyNoGeneratorPlatformVersion(
+  cmMakefile* mf, cm::optional<std::string> reason) const
+{
+  if (!this->GeneratorPlatformVersion) {
+    return true;
+  }
+  std::ostringstream e;
+  /* clang-format off */
+  e <<
+    "Generator\n"
+    "  " << this->GetName() << "\n"
+    "given platform specification containing a\n"
+    "  version=" << *this->GeneratorPlatformVersion << "\n"
+    "field.  The version field is not supported when targeting\n"
+    "  " << this->SystemName << " " << this->SystemVersion << "\n"
+    ;
+  /* clang-format on */
+  if (reason) {
+    e << *reason << ".";
+  }
+  mf->IssueMessage(MessageType::FATAL_ERROR, e.str());
+  return false;
 }
 
 bool cmGlobalVisualStudio14Generator::InitializeWindowsStore(cmMakefile* mf)
@@ -170,12 +194,42 @@ bool cmGlobalVisualStudio14Generator::InitializeAndroid(cmMakefile*)
   return true;
 }
 
+bool cmGlobalVisualStudio14Generator::ProcessGeneratorPlatformField(
+  std::string const& key, std::string const& value)
+{
+  if (key == "version") {
+    this->GeneratorPlatformVersion = value;
+    return true;
+  }
+  return false;
+}
+
 bool cmGlobalVisualStudio14Generator::SelectWindows10SDK(cmMakefile* mf)
 {
+  if (this->GeneratorPlatformVersion &&
+      this->GeneratorPlatformVersion->empty()) {
+    mf->IssueMessage(
+      MessageType::FATAL_ERROR,
+      cmStrCat("Generator\n  ", this->GetName(),
+               "\ngiven platform specification with empty\n  version=\n"
+               "field."));
+    return false;
+  }
+
   // Find the default version of the Windows 10 SDK.
   std::string const version = this->GetWindows10SDKVersion(mf);
 
   if (version.empty()) {
+    if (this->GeneratorPlatformVersion) {
+      mf->IssueMessage(
+        MessageType::FATAL_ERROR,
+        cmStrCat("Generator\n  ", this->GetName(),
+                 "\ngiven platform specification with\n  version=",
+                 *this->GeneratorPlatformVersion,
+                 "\nfield, but no Windows SDK with that version was found."));
+      return false;
+    }
+
     if (this->SystemName == "WindowsStore") {
       mf->IssueMessage(
         MessageType::FATAL_ERROR,
@@ -359,7 +413,20 @@ std::string cmGlobalVisualStudio14Generator::GetWindows10SDKVersion(
   // Sort the results to make sure we select the most recent one.
   std::sort(sdks.begin(), sdks.end(), cmSystemTools::VersionCompareGreater);
 
-  // Look for a SDK exactly matching the requested target version.
+  // Look for a SDK exactly matching the requested version, if any.
+  if (this->GeneratorPlatformVersion) {
+    for (std::string const& i : sdks) {
+      if (cmSystemTools::VersionCompareEqual(
+            i, *this->GeneratorPlatformVersion)) {
+        return i;
+      }
+    }
+    // An exact version was requested but not found.
+    // Our caller will issue the error message.
+    return std::string();
+  }
+
+  // Look for a SDK exactly matching the target Windows version.
   for (std::string const& i : sdks) {
     if (cmSystemTools::VersionCompareEqual(i, this->SystemVersion)) {
       return i;