[PATCH] avoid erroneous VLA bounds (PR 100550)

[Martin Sebor via Gcc-patches]

An erroneous VLA parameter bound in a function redeclaration causes
an ICE as the -Wvla-parameter is trying to format a diagnostic after
an error has already been issued.  The attached change prevents
such parameters from being considered.

This patch is for trunk and GCC 11.

Martin

PR c/100550 - ICE: in fold_convert_loc with function call VLA argument

gcc/c/ChangeLog:

	PR c/100550
	* c-decl.c (get_parm_array_spec): Avoid erroneous VLA bounds.

gcc/testsuite/ChangeLog:

	PR c/100550
	* gcc.dg/Wvla-parameter-9.c: New test.

diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 3ea4708c507..53b2b5b637d 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -5856,6 +5856,9 @@ get_parm_array_spec (const struct c_parm *parm, tree attrs)
 	  spec += buf;
 	  break;
 	}
+      else if (!INTEGRAL_TYPE_P (TREE_TYPE (nelts)))
+	/* Avoid invalid NELTS.  */
+	return attrs;
 
       /* Each variable VLA bound is represented by a dollar sign.  */
       spec += "$";
diff --git a/gcc/testsuite/gcc.dg/Wvla-parameter-9.c b/gcc/testsuite/gcc.dg/Wvla-parameter-9.c
new file mode 100644
index 00000000000..6c8987a34eb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wvla-parameter-9.c
@@ -0,0 +1,30 @@
+/* PR c/100550 - ICE: in fold_convert_loc with function call VLA argument
+   { dg-do compile }
+   { dg-options "-Wall" } */
+
+struct S { int i; };
+
+extern void v;
+extern void *pv;
+extern struct S s;
+void vf (void);
+
+/* Verify that a function redeclaration with an invalid VLA doesn't ICE.  */
+
+void f0 (int[]);
+void f0 (int[undeclared]);    // { dg-error "undeclared" }
+
+void f1 (int[]);
+void f1 (int[-1]);            // { dg-error "size" }
+
+void f2 (int[]);
+void f2 (int[v]);             // { dg-error "size" }
+
+void f3 (int[]);
+void f3 (int b[s]);           // { dg-error "size" }
+
+void f4 (int[]);
+void f4 (int c[pv]);          // { dg-error "size" }
+
+void f5 (int[]);
+void f5 (int d[vf ()]);       // { dg-error "size" }