[flang] Ignore empty keyword macros before directives (#130333)

Ignore any keyword macros with empty directives that might appear before
a compiler directive.

Fixes https://github.com/llvm/llvm-project/issues/126459.

1 files changed, 9 insertions, 0 deletions

diff --git a/flang/lib/Parser/preprocessor.cpp b/flang/lib/Parser/preprocessor.cpp
index 6c257f5..7e6a1c2 100644
--- a/flang/lib/Parser/preprocessor.cpp
+++ b/flang/lib/Parser/preprocessor.cpp
@@ -842,6 +842,15 @@ bool Preprocessor::IsNameDefined(const CharBlock &token) {
   return definitions_.find(token) != definitions_.end();
 }
 
+bool Preprocessor::IsNameDefinedEmpty(const CharBlock &token) {
+  if (auto it{definitions_.find(token)}; it != definitions_.end()) {
+    const Definition &def{it->second};
+    return !def.isFunctionLike() && def.replacement().SizeInChars() == 0;
+  } else {
+    return false;
+  }
+}
+
 bool Preprocessor::IsFunctionLikeDefinition(const CharBlock &token) {
   auto it{definitions_.find(token)};
   return it != definitions_.end() && it->second.isFunctionLike();