[flang][driver] Make the driver report diagnostics from the prescanner

[awarzynski]

Summary

This patch makes sure that diagnostics from the prescanner are reported
when running flang-new -E (i.e. only the preprocessor phase is
requested). More specifically, the PrintPreprocessedAction action is
updated.

With this patch we make sure that the f18 and flang-new provide
identical output when running the preprocessor and the prescanner
generates diagnostics.

Depends on: D93453

[kiranchandramohan]

flang/test/Frontend/preprocessor-diag.f90

8

Is the filename missing here? Can the driver preprocess and emit multiple files.

[sameeranjoshi]

flang/test/Frontend/preprocessor-diag.f90

8

Here's how it looks for multiple files.
I tried with f18 and not flang-new, with this patch I think both should ideally show the same output(at least it is supposed to).

temp.f90:2:20: #include: extra stuff ignored after file name
  #include <empty.h> <empty.h> comment
                                     ^^^^^^^^^^^^^^
temp.f90:4:20: #include: extra stuff ignored after file name
  #include "empty.h" <empty.h> comment
                                  ^^^^^^^^^^^^^^
end

10

I discovered just now that the output isn't a error but seems like a warning.
I feel using --check-prefix=WARNING would be correct.

[awarzynski]

Address PR comments

• Added filename in the test, thank you @kiranchandramohan !
• Updated the check prefix in the test, thank you @sameeranjoshi !

[awarzynski]

flang/test/Frontend/preprocessor-diag.f90

8

@sameeranjoshi Thank you for checking this! I've added the file name there. Both f18 and flang-new behave consistently here.

10

Good point, thank you! I'm hesitant to use WARNING, as there is nothing that it would indicate that it's actually a warning. FWIW, it's just a diagnostic message without any severity attached to it.

Are you OK with regular CHECK ?

[sameeranjoshi]

flang/test/Frontend/preprocessor-diag.f90

10

Go ahead.

flang/lib/Frontend/FrontendActions.cpp

void PrintPreprocessedAction::ExecuteAction() {
 
   // If a pre-defined output stream exists, dump the preprocessed content there
   if (!ci.IsOutputStreamNull()) {
     // Send the output to the pre-defined output buffer.
     ci.WriteOutputStream(outForPP.str());
     return;
   }
 
+  // Print diagnostics from the preprocessor
+  ci.parsing().messages().Emit(llvm::errs(), ci.allCookedSources());
+
   // Create a file and save the preprocessed output there
   if (auto os{ci.CreateDefaultOutputFile(
           /*Binary=*/true, /*InFile=*/GetCurrentFileOrBufferName())}) {
     (*os) << outForPP.str();
   } else {
     llvm::errs() << "Unable to create the output file\n";
     return;
   }

flang/test/Frontend/preprocessor-diag.f90

+! RUN: %f18 -E -I %S/Inputs/ %s 2>&1 | FileCheck %s
+! RUN: %flang-new -E -I %S/Inputs/ %s 2>&1 | FileCheck %s
+! RUN: %flang-new -fc1 -E -I %S/Inputs/ %s 2>&1 | FileCheck %s
+
+! Test that the driver correctly reports diagnostics from the prescanner. The contents of the include file are irrelevant here.
+
+! CHECK: preprocessor-diag.f90:8:20: #include: extra stuff ignored after file name
+#include <empty.h> comment
+! CHECK: preprocessor-diag.f90:10:20: #include: extra stuff ignored after file name
+#include "empty.h" comment
+end