From 2454ba9e2d1ce2d1b9b2b46f6111e022364bf9b5 Mon Sep 17 00:00:00 2001
From: Andrew Pinski <pinskia@gmail.com>
Date: Thu, 19 Oct 2023 05:42:02 +0000
Subject: [PATCH] c: Fix ICE when an argument was an error mark [PR100532]

In the case of convert_argument, we would return the same expression
back rather than error_mark_node after the error message about
trying to convert to an incomplete type. This causes issues in
the gimplfier trying to see if another conversion is needed.

The code here dates back to before the revision history too so
it might be the case it never noticed we should return an error_mark_node.

Bootstrapped and tested on x86_64-linux-gnu with no regressions.

	PR c/100532

gcc/c/ChangeLog:

	* c-typeck.cc (convert_argument): After erroring out
	about an incomplete type return error_mark_node.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr100532-1.c: New test.
---
 gcc/c/c-typeck.cc                 | 2 +-
 gcc/testsuite/gcc.dg/pr100532-1.c | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/pr100532-1.c

diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index f39dc71d5932..f7ce13ae7380 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -3367,7 +3367,7 @@ convert_argument (location_t ploc, tree function, tree fundecl,
     {
       error_at (ploc, "type of formal parameter %d is incomplete",
 		parmnum + 1);
-      return val;
+      return error_mark_node;
     }
 
   /* Optionally warn about conversions that differ from the default
diff --git a/gcc/testsuite/gcc.dg/pr100532-1.c b/gcc/testsuite/gcc.dg/pr100532-1.c
new file mode 100644
index 000000000000..81e37c60415c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr100532-1.c
@@ -0,0 +1,7 @@
+/* { dg-do compile } */
+/* PR c/100532 */
+
+typedef __SIZE_TYPE__ size_t;
+void *memcpy(void[], const void *, size_t); /* { dg-error "declaration of type name" } */
+void c(void) { memcpy(c, "a", 2); } /* { dg-error "type of formal parameter" } */
+
-- 
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