[clang] 5996306 - [C++20][Modules][Driver][HU 3/N] Handle foo.h with -fmodule-header and/or C++ invocation.

[Iain Sandoe via cfe-commits]

Author: Iain Sandoe
Date: 2022-04-23T09:50:31+01:00
New Revision: 5996306c24badac0e04c1cead1aed4b106a3bdae

URL: https://github.com/llvm/llvm-project/commit/5996306c24badac0e04c1cead1aed4b106a3bdae
DIFF: https://github.com/llvm/llvm-project/commit/5996306c24badac0e04c1cead1aed4b106a3bdae.diff

LOG: [C++20][Modules][Driver][HU 3/N] Handle foo.h with -fmodule-header and/or C++ invocation.

Allow an invocation like clang -fmodule-header bar.h (which will be a C++
compilation, but using a header which will be recognised as a C one).

Also  we do not want to produce:
 "treating 'c-header' input as 'c++-header' when in C++ mode"
diagnostics when the user has been specific about the intent.

Differential Revision: https://reviews.llvm.org/D121590

Added: 
    

Modified: 
    clang/lib/Driver/Driver.cpp
    clang/test/Driver/cxx20-header-units-02.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 0da079b1deb38..b453e24769571 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -2437,7 +2437,9 @@ void Driver::BuildInputs(const ToolChain &TC, DerivedArgList &Args,
             types::ID OldTy = Ty;
             Ty = types::lookupCXXTypeForCType(Ty);
 
-            if (Ty != OldTy)
+            // Do not complain about foo.h, when we are known to be processing
+            // it as a C++20 header unit.
+            if (Ty != OldTy && !(OldTy == types::TY_CHeader && hasHeaderMode()))
               Diag(clang::diag::warn_drv_treating_input_as_cxx)
                   << getTypeName(OldTy) << getTypeName(Ty);
           }
@@ -2462,8 +2464,11 @@ void Driver::BuildInputs(const ToolChain &TC, DerivedArgList &Args,
         }
 
         // Disambiguate headers that are meant to be header units from those
-        // intended to be PCH.
-        if (Ty == types::TY_CXXHeader && hasHeaderMode())
+        // intended to be PCH.  Avoid missing '.h' cases that are counted as
+        // C headers by default - we know we are in C++ mode and we do not
+        // want to issue a complaint about compiling things in the wrong mode.
+        if ((Ty == types::TY_CXXHeader || Ty == types::TY_CHeader) &&
+            hasHeaderMode())
           Ty = CXXHeaderUnitType(CXX20HeaderType);
       } else {
         assert(InputTypeArg && "InputType set w/o InputTypeArg");

diff  --git a/clang/test/Driver/cxx20-header-units-02.cpp b/clang/test/Driver/cxx20-header-units-02.cpp
index aab999cda2276..7b7a40f9e831f 100644
--- a/clang/test/Driver/cxx20-header-units-02.cpp
+++ b/clang/test/Driver/cxx20-header-units-02.cpp
@@ -3,6 +3,9 @@
 // RUN: %clang -### -std=c++20 -fmodule-header=user foo.hh  2>&1 | \
 // RUN:   FileCheck -check-prefix=CHECK-USER %s
 
+// RUN: %clang -### -std=c++20 -fmodule-header=user foo.h  2>&1 | \
+// RUN:   FileCheck -check-prefix=CHECK-USER1 %s
+
 // RUN: %clang -### -std=c++20 -fmodule-header=system foo.hh 2>&1 | \
 // RUN:   FileCheck -check-prefix=CHECK-SYS1 %s
 
@@ -19,6 +22,10 @@
 // CHECK-USER-SAME: "-o" "foo.pcm"
 // CHECK-USER-SAME: "-x" "c++-user-header" "foo.hh"
 
+// CHECK-USER1: "-emit-header-unit"
+// CHECK-USER1-SAME: "-o" "foo.pcm"
+// CHECK-USER1-SAME: "-x" "c++-user-header" "foo.h"
+
 // CHECK-SYS1: "-emit-header-unit"
 // CHECK-SYS1-SAME: "-o" "foo.pcm"
 // CHECK-SYS1-SAME: "-x" "c++-system-header" "foo.hh"