Fix for infinite recursion with macro invocation (#1177)

* First pass fix of macro expansion logic to stop recursive application (causting a recursive loop), whilst also allowing application on parameters to a macro.

* Added recursive-macro test.
Fixed macro application example.

1 files changed, 25 insertions, 0 deletions

diff --git a/tests/preprocessor/recursive-macro.slang b/tests/preprocessor/recursive-macro.slang
new file mode 100644
index 000000000..1f776ca72
--- /dev/null
+++ b/tests/preprocessor/recursive-macro.slang
@@ -0,0 +1,25 @@
+//TEST(compute):SIMPLE:
+
+// Test for correct recursive macro behavior. In particular: 
+
+// The letter of the spec is that we should macro expand
+// each argument *before* substitution, and then go and
+// macro-expand the substituted body. This means that we
+// can invoke a macro as part of an argument to an
+// invocation of the same macro:
+//
+//     FOO( 1, FOO(22, 2, 2), 333 );
+
+// Also in the case on NO_EXPAND, it will not be expanded in the substitution. 
+
+#define ARG_EXPAND(x) ( x )
+
+// This macro should expand to NO_EXPAND(int 'a'), and not multiply invoke NO_EXPAND, because
+// one the args have been expanded.
+#define NO_EXPAND(a) NO_EXPAND(int a)
+
+// Should expand to int NO_EXPAND(int b)
+int NO_EXPAND(b)
+{
+    return b + ARG_EXPAND(ARG_EXPAND(1));
+}
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