[clang] opencl: Ensure printf symbol is not mangled. (PR #150210)

[Felix Weiglhofer via cfe-commits]

https://github.com/fweig updated https://github.com/llvm/llvm-project/pull/150210

>From d7ef810cfc0751781751bc24ce9d1a4a6486080a Mon Sep 17 00:00:00 2001
From: Felix Weiglhofer <felix.weiglhofer at cern.ch>
Date: Mon, 28 Jul 2025 15:07:07 +0200
Subject: [PATCH] opencl: Ensure printf symbol is not mangled.

---
 clang/lib/Headers/opencl-c-base.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Headers/opencl-c-base.h b/clang/lib/Headers/opencl-c-base.h
index 2b7f5043e09e4..6206a347852be 100644
--- a/clang/lib/Headers/opencl-c-base.h
+++ b/clang/lib/Headers/opencl-c-base.h
@@ -697,7 +697,16 @@ template <typename _Tp> struct __remove_address_space<__constant _Tp> {
 #if defined(__OPENCL_CPP_VERSION__) || (__OPENCL_C_VERSION__ >= CL_VERSION_1_2)
 // OpenCL v1.2 s6.12.13, v2.0 s6.13.13 - printf
 
-int printf(__constant const char* st, ...) __attribute__((format(printf, 1, 2)));
+#ifdef __OPENCL_CPP_VERSION__
+#define CLINKAGE extern "C"
+#else
+#define CLINKAGE
+#endif
+
+CLINKAGE int printf(__constant const char *st, ...)
+    __attribute__((format(printf, 1, 2)));
+
+#undef CLINKAGE
 #endif
 
 #ifdef cl_intel_device_side_avc_motion_estimation