[clang][driver] Set the input type to Fortran when reading from stdin

[awarzynski]

Summary

This patch makes sure that for the following invocation of the new Flang
driver, clangDriver sets the input type to Fortran:

flang-new -E -

This change does not affect clang, i.e. for the following invocation
the input type is set to C:

clang -E -

This change leverages the fact that for flang-new the driver is in
Flang mode.

[SouraVX]

Thanks! for the patch.
This code touches some of the clang part, Anyway changes are pretty self-explanatory. I'll leave this one to you, if you want land it or wait from someone from clang community to take a look :)

[awarzynski]

In D96777#2578153, @SouraVX wrote:

Thanks! for the patch.
This code touches some of the clang part, Anyway changes are pretty self-explanatory. I'll leave this one to you, if you want land it or wait from someone from clang community to take a look :)

Thank you for reviewing!

Git history tells me that @hans touched this bit most recently - in 2014 :) Added as a reviewer - I will wait another day or two before merging.

[hans]

In D96777#2578473, @awarzynski wrote:

In D96777#2578153, @SouraVX wrote:

Thanks! for the patch.
This code touches some of the clang part, Anyway changes are pretty self-explanatory. I'll leave this one to you, if you want land it or wait from someone from clang community to take a look :)

Thank you for reviewing!

Git history tells me that @hans touched this bit most recently - in 2014 :) Added as a reviewer - I will wait another day or two before merging.

I don't remember what I did here in 2014, but this looks reasonable to me.

clang/lib/Driver/Driver.cpp

if (A->getOption().getKind() == Option::InputClass) {
       // Infer the input type if necessary.
       if (InputType == types::TY_Nothing) {
         // If there was an explicit arg for this, claim it.
         if (InputTypeArg)
           InputTypeArg->claim();
 
         // stdin must be handled specially.
         if (memcmp(Value, "-", 2) == 0) {
-          // If running with -E, treat as a C input (this changes the builtin
-          // macros, for example). This may be overridden by -ObjC below.
+          if (IsFlangMode()) {
+            Ty = types::TY_Fortran;
+          } else {
+            // If running with -E, treat as a C input (this changes the
+            // builtin macros, for example). This may be overridden by -ObjC
+            // below.
             //
             // Otherwise emit an error but still use a valid type to avoid
             // spurious errors (e.g., no inputs).
             if (!Args.hasArgNoClaim(options::OPT_E) && !CCCIsCPP())
               Diag(IsCLMode() ? clang::diag::err_drv_unknown_stdin_type_clang_cl
                               : clang::diag::err_drv_unknown_stdin_type);
             Ty = types::TY_C;
+          }
         } else {
           // Otherwise lookup by extension.
           // Fallback is C if invoked as C preprocessor, C++ if invoked with
           // clang-cl /E, or Object otherwise.
           // We use a host hook here because Darwin at least has its own
           // idea of what .s is.
           if (const char *Ext = strrchr(Value, '.'))
             Ty = TC.LookupTypeForExtension(Ext + 1);

flang/test/Flang-Driver/input-from-stdin.f90

 ! Verify that reading from stdin works as expected
 
 ! REQUIRES: new-flang-driver
 
 !--------------------------
 ! FLANG DRIVER (flang-new)
 !--------------------------
-! TODO: Add support for `flang-new -`
-! Currently `bin/flang-new  -E -` defaults to `-x c` and e.g. F90 is not allowed
-! in `-x <input-type>` (see `clang::driver::types::canTypeBeUserSpecified` in
-! Types.cpp)
+! Input type is implicit
+! RUN: cat %s | flang-new -E - | FileCheck %s --check-prefix=PP-NOT-DEFINED
+! RUN: cat %s | flang-new -DNEW -E - | FileCheck %s --check-prefix=PP-DEFINED
+
+! Input type is explicit
+! RUN: cat %s | flang-new -E -x f95-cpp-input - | FileCheck %s --check-prefix=PP-NOT-DEFINED
+! RUN: cat %s | flang-new -DNEW -E -x f95-cpp-input - | FileCheck %s --check-prefix=PP-DEFINED
 
 !---------------------------------------
 ! FLANG FRONTEND DRIVER (flang-new -fc1)
 !---------------------------------------
-! Test `-E` - for the corresponding frontend actions the driver relies on the prescanner API to handle file I/O
+! Test `-E`: for the corresponding frontend actions the driver relies on the prescanner API to handle file I/O
 ! RUN: cat %s | flang-new -fc1 -E | FileCheck %s --check-prefix=PP-NOT-DEFINED
 ! RUN: cat %s | flang-new -fc1 -DNEW -E | FileCheck %s --check-prefix=PP-DEFINED
 
-! Test `-test-io` - for the corresponding frontend action (`InputOutputTestAction`) the driver handles the file I/O on its own
+! Test `-test-io`: for the corresponding frontend action (`InputOutputTestAction`) the driver handles the file I/O on its own
 ! the corresponding action (`PrintPreprocessedAction`)
 ! RUN: cat %s | flang-new -fc1 -test-io | FileCheck %s --check-prefix=IO --match-full-lines
 ! RUN: cat %s | flang-new -fc1 -DNEW -test-io | FileCheck %s --check-prefix=IO --match-full-lines
 
 !-------------------------
 ! EXPECTED OUTPUT for `-E`
 !-------------------------
 ! PP-NOT-DEFINED: program b