gccrs: Fix infinite loop with missing comma

A missing comma between inline assembly templates did not throw an error
and looped indefinitely.

gcc/rust/ChangeLog:

	* expand/rust-macro-builtins-asm.cc (parse_format_strings): Emit an
	error when expecting a comma.

gcc/testsuite/ChangeLog:

	* rust/compile/issue-4006.rs: New test.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/gcc/testsuite/rust/compile/issue-4006.rs b/gcc/testsuite/rust/compile/issue-4006.rs
new file mode 100644
index 0000000..328c7b6
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-4006.rs
@@ -0,0 +1,13 @@
+#![feature(rustc_attrs)]
+
+#[rustc_builtin_macro]
+macro_rules! asm {
+    () => {};
+}
+
+pub fn main() {
+    asm!(
+        "xor eax, eax"
+        "xor eax, eax");
+    // { dg-error "expected token .;." "" { target *-*-* } .-1 }
+}