[flang][preprocessor] Change handling of macros in text from Fortran … (#108113)

…INCLUDE lines

The compiler current treats an INCLUDE line as essentially a synonym for
a preprocessing #include directive. The causes macros that have been
defined at the point where the INCLUDE line is processed to be replaced
within the text of the included file.

This behavior is surprising to users who expect an INCLUDE line to be
expanded into its contents *after* preprocessing has been applied to the
original source file, with no further macro expansion.

Change INCLUDE line processing to use a fresh instance of Preprocessor
containing no macro definitions except _CUDA in CUDA Fortran
compilations and, if the original file was being preprocessed, the
standard definitions of __FILE__, __LINE__, and so forth.

1 files changed, 1 insertions, 1 deletions

diff --git a/flang/lib/Parser/preprocessor.cpp b/flang/lib/Parser/preprocessor.cpp
index 7d3130c..cb3725b 100644
--- a/flang/lib/Parser/preprocessor.cpp
+++ b/flang/lib/Parser/preprocessor.cpp
@@ -769,7 +769,7 @@ void Preprocessor::Directive(const TokenSequence &dir, Prescanner &prescanner) {
       if (included->bytes() > 0) {
         ProvenanceRange fileRange{
             allSources_.AddIncludedFile(*included, dir.GetProvenanceRange())};
-        Prescanner{prescanner, /*isNestedInIncludeDirective=*/true}
+        Prescanner{prescanner, *this, /*isNestedInIncludeDirective=*/true}
             .set_encoding(included->encoding())
             .Prescan(fileRange);
       }