c: ignore initializers for elements of variable-size types [PR93577]

Bug 93577, apparently a regression (although it isn't very clear to me
exactly when it was introduced; tests I made with various past
compilers produced inconclusive results, including e.g. ICEs appearing
with 64-bit-host compilers for some versions but not 32-bit-host
compilers for the same versions) is an C front-end tree-checking ICE
processing initializers for structs using the VLA-in-struct extension.
There is an error for such initializers, but other processing that
still takes place for them results in the ICE.

This patch ensures that processing of initializers for variable-size
types stops earlier to avoid the code that results in the ICE (and
ensures it stops earlier for error_mark_node to avoid ICEs in the
check for variable-size types), adjusts the conditions for the "empty
scalar initializer" diagnostic to avoid consequent excess errors in
the case of a bad type name, and adds tests for a few variations on
what such initializers might look like, as well as tests for cases
identified from ICEs seen with an earlier version of this patch.

Bootstrapped with no regressions for x86_64-pc-linux-gnu.

	PR c/93577
gcc/c:
	* c-typeck.c (pop_init_level): Do not diagnose initializers as
	empty when initialized type is error_mark_node.
	(set_designator, process_init_element): Ignore initializers for
	elements of a variable-size type or of error_mark_node.

gcc/testsuite:
	* gcc.dg/pr93577-1.c, gcc.dg/pr93577-2.c, gcc.dg/pr93577-3.c,
	gcc.dg/pr93577-4.c, gcc.dg/pr93577-5.c, gcc.dg/pr93577-6.c: New
	tests.
	* gcc.dg/vla-init-1.c: Expect fewer errors about VLA initializer.

gcc/c/ChangeLog

@@ -1,3 +1,11 @@
+2020-03-05  Joseph Myers  <joseph@codesourcery.com>
+
+	PR c/93577
+	* c-typeck.c (pop_init_level): Do not diagnose initializers as
+	empty when initialized type is error_mark_node.
+	(set_designator, process_init_element): Ignore initializers for
+	elements of a variable-size type or of error_mark_node.
+
 2020-03-01  Martin Sebor  <msebor@redhat.com>
 
 	PR middle-end/93926

gcc/c/c-typeck.c

@@ -8759,7 +8759,7 @@ pop_init_level (location_t loc, int implicit,
 	 the element, after verifying there is just one.  */
       if (vec_safe_is_empty (constructor_elements))
 	{
-	  if (!constructor_erroneous)
+	  if (!constructor_erroneous && constructor_type != error_mark_node)
 	    error_init (loc, "empty scalar initializer");
 	  ret.value = error_mark_node;
 	}
@@ -8836,8 +8836,8 @@ set_designator (location_t loc, bool array,
   enum tree_code subcode;
 
   /* Don't die if an entire brace-pair level is superfluous
-     in the containing level.  */
-  if (constructor_type == NULL_TREE)
+     in the containing level, or for an erroneous type.  */
+  if (constructor_type == NULL_TREE || constructor_type == error_mark_node)
     return true;
 
   /* If there were errors in this designator list already, bail out
@@ -8845,6 +8845,12 @@ set_designator (location_t loc, bool array,
   if (designator_erroneous)
     return true;
 
+  /* Likewise for an initializer for a variable-size type.  Those are
+     diagnosed in digest_init.  */
+  if (COMPLETE_TYPE_P (constructor_type)
+      && TREE_CODE (TYPE_SIZE (constructor_type)) != INTEGER_CST)
+    return true;
+
   if (!designator_depth)
     {
       gcc_assert (!constructor_range_stack);
@@ -9955,8 +9961,14 @@ process_init_element (location_t loc, struct c_expr value, bool implicit,
     }
 
   /* Ignore elements of a brace group if it is entirely superfluous
-     and has already been diagnosed.  */
-  if (constructor_type == NULL_TREE)
+     and has already been diagnosed, or if the type is erroneous.  */
+  if (constructor_type == NULL_TREE || constructor_type == error_mark_node)
+    return;
+
+  /* Ignore elements of an initializer for a variable-size type.
+     Those are diagnosed in digest_init.  */
+  if (COMPLETE_TYPE_P (constructor_type)
+      && TREE_CODE (TYPE_SIZE (constructor_type)) != INTEGER_CST)
     return;
 
   if (!implicit && warn_designated_init && !was_designated

gcc/testsuite/ChangeLog

@@ -1,3 +1,11 @@
+2020-03-05  Joseph Myers  <joseph@codesourcery.com>
+
+	PR c/93577
+	* gcc.dg/pr93577-1.c, gcc.dg/pr93577-2.c, gcc.dg/pr93577-3.c,
+	gcc.dg/pr93577-4.c, gcc.dg/pr93577-5.c, gcc.dg/pr93577-6.c: New
+	tests.
+	* gcc.dg/vla-init-1.c: Expect fewer errors about VLA initializer.
+
 2020-03-05  Jeff Law  <law@redhat.com>
 
 	PR tree-optimization/91890

gcc/testsuite/gcc.dg/pr93577-1.c

@@ -0,0 +1,16 @@
+/* Test ICE with variable-size struct initializer: bug 93577.  */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void
+f (int c)
+{
+  struct s
+  {
+    int x[c];
+    struct
+    {
+      int z;
+    } nest;
+  } v = { 1, 2 }; /* { dg-error "variable-sized object may not be initialized" } */
+}

gcc/testsuite/gcc.dg/pr93577-2.c

@@ -0,0 +1,16 @@
+/* Test ICE with variable-size struct initializer: bug 93577.  */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void
+f (int c)
+{
+  struct s
+  {
+    int x[c];
+    struct
+    {
+      int a, b;
+    } nest;
+  } v = { .nest.b = 1, .nest.a = 2 }; /* { dg-error "variable-sized object may not be initialized" } */
+}

gcc/testsuite/gcc.dg/pr93577-3.c

@@ -0,0 +1,17 @@
+/* Test ICE with variable-size struct initializer: bug 93577.  */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void
+f (int c)
+{
+  struct s
+  {
+    int a;
+    int x[c];
+    struct
+    {
+      int a, b;
+    } nest;
+  } v = { .a = 2, .nest.b = 1 }; /* { dg-error "variable-sized object may not be initialized" } */
+}

gcc/testsuite/gcc.dg/pr93577-4.c

@@ -0,0 +1,17 @@
+/* Test ICE with variable-size struct initializer: bug 93577.  */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void
+f (int c)
+{
+  struct s
+  {
+    int a;
+    int x[c];
+    struct
+    {
+      int a, b;
+    } nest;
+  } v[2] = { [1].nest.b = 1 }; /* { dg-error "variable-sized object may not be initialized" } */
+}

gcc/testsuite/gcc.dg/pr93577-5.c

@@ -0,0 +1,11 @@
+/* Test ICE with designated initializer in compound literal with bad
+   type name (ICE seen with early version of fix for bug 93577 but not
+   covered in other tests).  */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void *
+f (void)
+{
+  return &(const bad_type) { .a = 0 }; /* { dg-error "unknown type name" } */
+}

gcc/testsuite/gcc.dg/pr93577-6.c

@@ -0,0 +1,11 @@
+/* Test ICE with designated initializer in compound literal with bad
+   type name (ICE seen with early version of fix for bug 93577 but not
+   covered in other tests).  */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void *
+f (void)
+{
+  return &(const bad_type) { [0] = 0 }; /* { dg-error "unknown type name" } */
+}

gcc/testsuite/gcc.dg/vla-init-1.c

@@ -10,6 +10,4 @@ void
 foo (void)
 {
   int x[a] = { 1 }; /* { dg-error "variable-sized object may not be initialized" "VLA init" } */
-  /* { dg-warning "excess elements in array initializer" "excess" { target *-*-* } .-1 } */
-  /* { dg-message "near initialization" "near" { target *-*-* } .-2 } */
 }