[clang] [clang] Ensure fixed point conversions work in C++ (PR #68344)

[John McCall via cfe-commits]

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@@ -1,6 +1,8 @@
 // NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
-// RUN: %clang_cc1 -ffixed-point -triple x86_64-unknown-linux-gnu -S -emit-llvm %s -o - | FileCheck %s --check-prefixes=CHECK,SIGNED
-// RUN: %clang_cc1 -ffixed-point -triple x86_64-unknown-linux-gnu -S -emit-llvm %s -o - -fpadding-on-unsigned-fixed-point | FileCheck %s --check-prefixes=CHECK,UNSIGNED
+// RUN: %clang_cc1 -x c -ffixed-point -triple x86_64-unknown-linux-gnu -S -emit-llvm %s -o - | FileCheck %s --check-prefixes=CHECK,SIGNED
+// RUN: %clang_cc1 -x c -ffixed-point -triple x86_64-unknown-linux-gnu -S -emit-llvm %s -o - -fpadding-on-unsigned-fixed-point | FileCheck %s --check-prefixes=CHECK,UNSIGNED
+// RUN: %clang_cc1 -x c++ -ffixed-point -triple x86_64-unknown-linux-gnu -S -emit-llvm %s -o - | FileCheck %s --check-prefixes=CHECK-CXX,SIGNED-CXX
+// RUN: %clang_cc1 -x c++ -ffixed-point -triple x86_64-unknown-linux-gnu -S -emit-llvm %s -o - -fpadding-on-unsigned-fixed-point | FileCheck %s --check-prefixes=CHECK-CXX,UNSIGNED-CXX
 
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rjmccall wrote:

Is there a reasonable way to not have to duplicate all of the tests here?  How close do you get if you just put the entire file in an `extern "C"` so that they mangle the same?

https://github.com/llvm/llvm-project/pull/68344