Diagnose recursive project/enable_language without crashing (#15999)

Calling `project()` or `enable_language()` from a toolchain file will
infinitely recurse since those commands load the toolchain file.
Diagnose and reject this case with an error message instead of crashing
when the stack eventually overflows.

1 files changed, 21 insertions, 0 deletions

diff --git a/Source/cmGlobalGenerator.cxx b/Source/cmGlobalGenerator.cxx
index 848028ff31..c6284069e4 100644
--- a/Source/cmGlobalGenerator.cxx
+++ b/Source/cmGlobalGenerator.cxx
@@ -398,6 +398,21 @@ cmGlobalGenerator::EnableLanguage(std::vector<std::string>const& languages,
     return;
     }
 
+  std::set<std::string> cur_languages(languages.begin(), languages.end());
+  for (std::set<std::string>::iterator li = cur_languages.begin();
+       li != cur_languages.end(); ++li)
+    {
+    if (!this->LanguagesInProgress.insert(*li).second)
+      {
+      std::ostringstream e;
+      e << "Language '" << *li << "' is currently being enabled.  "
+        "Recursive call not allowed.";
+      mf->IssueMessage(cmake::FATAL_ERROR, e.str());
+      cmSystemTools::SetFatalErrorOccured();
+      return;
+      }
+    }
+
   if(this->TryCompileOuterMakefile)
     {
     // In a try-compile we can only enable languages provided by caller.
@@ -823,6 +838,12 @@ cmGlobalGenerator::EnableLanguage(std::vector<std::string>const& languages,
     {
     cmSystemTools::SetFatalErrorOccured();
     }
+
+  for (std::set<std::string>::iterator li = cur_languages.begin();
+       li != cur_languages.end(); ++li)
+    {
+    this->LanguagesInProgress.erase(*li);
+    }
 }
 
 //----------------------------------------------------------------------------