[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.

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);
       }

flang/lib/Parser/prescan.cpp

@@ -32,10 +32,10 @@ Prescanner::Prescanner(Messages &messages, CookedSource &cooked,
       backslashFreeFormContinuation_{preprocessor.AnyDefinitions()},
       encoding_{allSources_.encoding()} {}
 
-Prescanner::Prescanner(const Prescanner &that, bool isNestedInIncludeDirective)
-    : messages_{that.messages_}, cooked_{that.cooked_},
-      preprocessor_{that.preprocessor_}, allSources_{that.allSources_},
-      features_{that.features_},
+Prescanner::Prescanner(const Prescanner &that, Preprocessor &prepro,
+    bool isNestedInIncludeDirective)
+    : messages_{that.messages_}, cooked_{that.cooked_}, preprocessor_{prepro},
+      allSources_{that.allSources_}, features_{that.features_},
       isNestedInIncludeDirective_{isNestedInIncludeDirective},
       backslashFreeFormContinuation_{that.backslashFreeFormContinuation_},
       inFixedForm_{that.inFixedForm_},
@@ -1104,7 +1104,14 @@ void Prescanner::FortranInclude(const char *firstQuote) {
         provenance, static_cast<std::size_t>(p - nextLine_)};
     ProvenanceRange fileRange{
         allSources_.AddIncludedFile(*included, includeLineRange)};
-    Prescanner{*this, /*isNestedInIncludeDirective=*/false}
+    Preprocessor cleanPrepro{allSources_};
+    if (preprocessor_.IsNameDefined("__FILE__"s)) {
+      cleanPrepro.DefineStandardMacros(); // __FILE__, __LINE__, &c.
+    }
+    if (preprocessor_.IsNameDefined("_CUDA"s)) {
+      cleanPrepro.Define("_CUDA"s, "1");
+    }
+    Prescanner{*this, cleanPrepro, /*isNestedInIncludeDirective=*/false}
         .set_encoding(included->encoding())
         .Prescan(fileRange);
   }

flang/lib/Parser/prescan.h

@@ -35,7 +35,8 @@ class Prescanner {
 public:
   Prescanner(Messages &, CookedSource &, Preprocessor &,
       common::LanguageFeatureControl);
-  Prescanner(const Prescanner &, bool isNestedInIncludeDirective);
+  Prescanner(
+      const Prescanner &, Preprocessor &, bool isNestedInIncludeDirective);
   Prescanner(const Prescanner &) = delete;
   Prescanner(Prescanner &&) = delete;
 

flang/module/__fortran_builtins.f90

@@ -6,7 +6,7 @@
 !
 !===------------------------------------------------------------------------===!
 
-include '../include/flang/Runtime/magic-numbers.h'
+#include '../include/flang/Runtime/magic-numbers.h'
 
 ! These naming shenanigans prevent names from Fortran intrinsic modules
 ! from being usable on INTRINSIC statements, and force the program

flang/module/__fortran_ieee_exceptions.f90

@@ -11,7 +11,7 @@
 ! here under another name so that IEEE_ARITHMETIC can USE it and export its
 ! declarations without clashing with a non-intrinsic module in a program.
 
-include '../include/flang/Runtime/magic-numbers.h'
+#include '../include/flang/Runtime/magic-numbers.h'
 
 module __fortran_ieee_exceptions
   use __fortran_builtins, only: &

flang/module/ieee_arithmetic.f90

@@ -8,7 +8,7 @@
 
 ! Fortran 2018 Clause 17
 
-include '../include/flang/Runtime/magic-numbers.h'
+#include '../include/flang/Runtime/magic-numbers.h'
 
 module ieee_arithmetic
   ! F18 Clause 17.1p1:

flang/module/iso_fortran_env.f90

@@ -8,7 +8,7 @@
 
 ! See Fortran 2023, subclause 16.10.2
 
-include '../include/flang/Runtime/magic-numbers.h'
+#include '../include/flang/Runtime/magic-numbers.h'
 
 module iso_fortran_env
 

flang/test/Driver/include-header.f90

@@ -51,7 +51,7 @@ program B
 end
 
 ! include-test-two.f90
-INCLUDE "basic-header-two.h"
+#include "basic-header-two.h"
 #ifdef Y
 program Y
 #else

flang/test/Preprocessing/include-file.h

@@ -0,0 +1 @@
+print *, sin(0.), j

flang/test/Preprocessing/include-line.F90

@@ -0,0 +1,6 @@
+! RUN: %flang_fc1 -fdebug-unparse %s -Dj=1 2>&1 | FileCheck %s
+! Ensure that macro definitions don't affect INCLUDE lines (unlike #include)
+#define sin cos
+!CHECK: PRINT *, 0._4, j
+include "include-file.h"
+end