From: Jakub Jelinek <jakub@redhat.com>
Date: Thu, 13 Feb 2020 20:00:09 +0000 (+0100)
Subject: c: Fix ICE with cast to VLA [93576]
X-Git-Tag: releases/gcc-9.3.0~134
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7276dd4c7480dd952f0d4a9322ca04ca29f5126f;p=thirdparty%2Fgcc.git

c: Fix ICE with cast to VLA [93576]

The following testcase ICEs, because the PR84305 changes try to evaluate
the size earlier.  If size has side-effects, that is desirable, and the
side-effects will actually be wrapped in a SAVE_EXPR.  The problem on this
testcase is that there are no side-effects, and c_fully_fold doesn't fold
those COMPOUND_EXPRs to constant, and while before gimplification we unshare
trees found in the expressions, the unsharing doesn't involve TYPE_SIZE etc.
of used types.  Gimplification is destructive though, so when we gimplify
the two nested COMPOUND_EXPRs and then try to gimplify it the second time
for the TYPE_SIZEs, we ICE.
Now, we could use unshare_expr in what we push to *expr, SAVE_EXPRs and
their operands in there aren't unshared, but I really don't see a point of
evaluating expressions that don't have side-effects before, so instead
this just pushes there expressions that do have side-effects.

2020-02-13  Jakub Jelinek  <jakub@redhat.com>

	PR c/93576
	* c-decl.c (grokdeclarator): If this_size_varies, only push size into
	*expr if it has side effects.

	* gcc.dg/pr93576.c: New test.
---

diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index b17ed98a9aed..5ba4516e114a 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,9 @@
+2020-02-13  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/93576
+	* c-decl.c (grokdeclarator): If this_size_varies, only push size into
+	*expr if it has side effects.
+
 2020-01-22  Joseph Myers  <joseph@codesourcery.com>
 
 	Backport from mainline:
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index f77fb1739ca7..859a62412583 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -6368,11 +6368,14 @@ grokdeclarator (const struct c_declarator *declarator,
 		  }
 		if (this_size_varies)
 		  {
-		    if (*expr)
-		      *expr = build2 (COMPOUND_EXPR, TREE_TYPE (size),
-				      *expr, size);
-		    else
-		      *expr = size;
+		    if (TREE_SIDE_EFFECTS (size))
+		      {
+			if (*expr)
+			  *expr = build2 (COMPOUND_EXPR, TREE_TYPE (size),
+					  *expr, size);
+			else
+			  *expr = size;
+		      }
 		    *expr_const_operands &= size_maybe_const;
 		  }
 	      }
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 114a1087936a..24e5e88d7632 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2020-02-13  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c/93576
+	* gcc.dg/pr93576.c: New test.
+
 	PR target/93696
 	* gcc.target/i386/pr93696-1.c: New test.
 	* gcc.target/i386/pr93696-2.c: New test.
diff --git a/gcc/testsuite/gcc.dg/pr93576.c b/gcc/testsuite/gcc.dg/pr93576.c
new file mode 100644
index 000000000000..13c34f3771ff
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr93576.c
@@ -0,0 +1,10 @@
+/* PR c/93576 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void
+foo (void)
+{
+  int b[] = { 0 };
+  (char (*)[(1, 7, 2)]) 0;
+}