[clang] b37b10d - [Driver][SYCL] Treat stdin as C++ when -fsycl is active (#204968)

[via cfe-commits]

Author: Wenju He
Date: 2026-06-25T07:58:54+08:00
New Revision: b37b10d5217b992180ee0a61f343b3edb4cc083e

URL: https://github.com/llvm/llvm-project/commit/b37b10d5217b992180ee0a61f343b3edb4cc083e
DIFF: https://github.com/llvm/llvm-project/commit/b37b10d5217b992180ee0a61f343b3edb4cc083e.diff

LOG: [Driver][SYCL] Treat stdin as C++ when -fsycl is active (#204968)

1723b7a30145 added a frontend check that rejects C inputs when SYCL mode
is active (since SYCL requires C++). The stdin path in BuildInputs
hardcoded TY_C regardless of driver mode, so `-fsycl -dM -E -` would
pass -x c to cc1 and trigger the new diagnostic.

Fix: use TY_CXX for stdin when IsSYCL.

Also, upstream a downstream test that fails due to 1723b7a30145.

---------

Co-authored-by: Claude Sonnet 4.6 <noreply at anthropic.com>

Added: 
    clang/test/Driver/sycl-print-internal-defines.cpp

Modified: 
    clang/lib/Driver/Driver.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 40953c0013f62..eb87bd2eebad0 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -3134,6 +3134,8 @@ void Driver::BuildInputs(const ToolChain &TC, DerivedArgList &Args,
       Diag(clang::diag::warn_drv_unused_x) << LastXArg->getValue();
   }
 
+  bool IsSYCL = Args.hasFlag(options::OPT_fsycl, options::OPT_fno_sycl, false);
+
   for (Arg *A : Args) {
     if (A->getOption().getKind() == Option::InputClass) {
       const char *Value = A->getValue();
@@ -3151,6 +3153,8 @@ void Driver::BuildInputs(const ToolChain &TC, DerivedArgList &Args,
             Ty = types::TY_Fortran;
           } else if (IsDXCMode()) {
             Ty = types::TY_HLSL;
+          } else if (IsSYCL) {
+            Ty = types::TY_CXX;
           } else {
             // If running with -E, treat as a C input (this changes the
             // builtin macros, for example). This may be overridden by -ObjC

diff  --git a/clang/test/Driver/sycl-print-internal-defines.cpp b/clang/test/Driver/sycl-print-internal-defines.cpp
new file mode 100644
index 0000000000000..389aaf25608c6
--- /dev/null
+++ b/clang/test/Driver/sycl-print-internal-defines.cpp
@@ -0,0 +1,8 @@
+// Test that clang can print defines in SYCL mode.
+
+// RUN: %clangxx -fsycl -dM -E %s 2>&1 | FileCheck --check-prefix CHECK-PRINT-INTERNAL-DEFINES %s
+// CHECK-PRINT-INTERNAL-DEFINES: #define
+
+// Printing defines also works when input is stdin.
+// RUN: %clangxx -fsycl -dM -E - < /dev/null 2>&1 | FileCheck --check-prefixes=CHECK-PRINT-INTERNAL-DEFINES,CHECK-NO-ERROR %s
+// CHECK-NO-ERROR-NOT: error: