[gcc/devel/rust/master] Add a test for the cfg!() macro

[gcc/devel/rust/master] Add a test for the cfg!() macro

[Thomas Schwinge]

https://gcc.gnu.org/g:9a56a0d10d991d066188dedb89d19119146a17a0

commit 9a56a0d10d991d066188dedb89d19119146a17a0
Author: antego <antego@users.noreply.github.com>
Date:   Wed Apr 13 20:00:54 2022 +1000

    Add a test for the cfg!() macro
    
    See #1116 and #1039

Diff:
---
 .../rust/execute/torture/builtin_macro_cfg.rs      | 27 ++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/gcc/testsuite/rust/execute/torture/builtin_macro_cfg.rs b/gcc/testsuite/rust/execute/torture/builtin_macro_cfg.rs
new file mode 100644
index 00000000000..ac24791bd6a
--- /dev/null
+++ b/gcc/testsuite/rust/execute/torture/builtin_macro_cfg.rs
@@ -0,0 +1,27 @@
+// { dg-additional-options "-w -frust-cfg=A" }
+// { dg-output "A\n" }
+macro_rules! cfg {
+    () => {{}};
+}
+
+extern "C" {
+    fn printf(fmt: *const i8, ...);
+}
+
+fn print(s: &str) {
+    printf("%s\n" as *const str as *const i8, s as *const str as *const i8);
+}
+
+
+fn main() -> i32 {
+    let cfg = cfg!(A);
+    if cfg {
+        print("A");
+    }
+    let cfg = cfg!(B);
+    if cfg {
+        print("B");
+    }
+
+    0
+}