[PATCH] c: After issuing errors about array size, for error-recovery don't make the array VLA [PR93573]

[Jakub Jelinek via Gcc-patches]

Hi!

After we report various errors about array size, we set for error-recovery
the size to be 1, but because size_int_const is false, it still means we
pretend the array is a VLA, can emit a second diagnostics in that case etc.
E.g.
$ ./cc1.unpatched -quiet a.c
a.c:1:5: error: size of array ‘f’ has non-integer type
    1 | int f[100.0];
      |     ^
a.c:1:1: warning: variably modified ‘f’ at file scope
    1 | int f[100.0];
      | ^~~
$ ./cc1 -quiet a.c
a.c:1:5: error: size of array ‘f’ has non-integer type
    1 | int f[100.0];
      |     ^

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2020-03-28  Jakub Jelinek  <ja...@redhat.com>

        PR c/93573
        * c-decl.c (grokdeclarator): After issuing errors, set size_int_const
        to true after setting size to integer_one_node.

        * gcc.dg/pr93573-1.c: New test.

--- gcc/c/c-decl.c.jj   2020-03-19 22:55:50.107685767 +0100
+++ gcc/c/c-decl.c      2020-03-27 17:54:16.017024925 +0100
@@ -6416,6 +6416,7 @@ grokdeclarator (const struct c_declarato
                      error_at (loc,
                                "size of unnamed array has non-integer type");
                    size = integer_one_node;
+                   size_int_const = true;
                  }
                /* This can happen with enum forward declaration.  */
                else if (!COMPLETE_TYPE_P (TREE_TYPE (size)))
@@ -6427,6 +6428,7 @@ grokdeclarator (const struct c_declarato
                      error_at (loc, "size of unnamed array has incomplete "
                                "type");
                    size = integer_one_node;
+                   size_int_const = true;
                  }
 
                size = c_fully_fold (size, false, &size_maybe_const);
@@ -6451,6 +6453,7 @@ grokdeclarator (const struct c_declarato
                        else
                          error_at (loc, "size of unnamed array is negative");
                        size = integer_one_node;
+                       size_int_const = true;
                      }
                    /* Handle a size folded to an integer constant but
                       not an integer constant expression.  */
--- gcc/testsuite/gcc.dg/pr93573-1.c.jj 2020-03-27 17:55:39.085781301 +0100
+++ gcc/testsuite/gcc.dg/pr93573-1.c    2020-03-27 17:56:35.168941677 +0100
@@ -0,0 +1,12 @@
+/* PR c/93573 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void bar ();
+
+void
+foo (char a)
+{
+  union C { int d[100.0]; char *e; };  /* { dg-error "has non-integer type" } 
*/
+  bar ((union C) &a);
+}

        Jakub