[gtk/wip/kalev/gcc-11] Avoid diagnostics for gcc-11 false positive out of bounds accesses

[Kalev Lember <klember src gnome org>]

commit 71965b8392d34ecc8ef2ae0a1dd3be372d1e167f
Author: Kalev Lember <klember redhat com>
Date:   Sun Jan 10 09:35:40 2021 +0100

    Avoid diagnostics for gcc-11 false positive out of bounds accesses
    
    This is a patch by Jeff Law <law redhat com> done in downstream Fedora
    to fix the build with gcc 11.

 gtk/gtktextchild.c   | 14 ++++++++++++++
 gtk/gtktextsegment.c |  8 ++++++++
 2 files changed, 22 insertions(+)
---
diff --git a/gtk/gtktextchild.c b/gtk/gtktextchild.c
index 4d5e30e44f..915b9917dd 100644
--- a/gtk/gtktextchild.c
+++ b/gtk/gtktextchild.c
@@ -169,6 +169,12 @@ const GtkTextLineSegmentClass gtk_text_paintable_type = {
 GtkTextLineSegment *
 _gtk_paintable_segment_new (GdkPaintable *paintable)
 {
+  /* gcc-11 issues a diagnostic here because the size allocated
+     for SEG does not cover the entire size of a GtkTextLineSegment
+     and gcc has no way to know that the union will only be used
+     for limited types and the additional space is not needed.  */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Warray-bounds"
   GtkTextLineSegment *seg;
   guint flags;
 
@@ -204,6 +210,7 @@ _gtk_paintable_segment_new (GdkPaintable *paintable)
   g_object_ref (paintable);
 
   return seg;
+#pragma GCC diagnostic pop
 }
 
 
@@ -280,6 +287,12 @@ const GtkTextLineSegmentClass gtk_text_child_type = {
 GtkTextLineSegment *
 _gtk_widget_segment_new (GtkTextChildAnchor *anchor)
 {
+  /* gcc-11 issues a diagnostic here because the size allocated
+     for SEG does not cover the entire size of a GtkTextLineSegment
+     and gcc has no way to know that the union will only be used
+     for limited types and the additional space is not needed.  */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Warray-bounds"
   GtkTextLineSegment *seg;
 
   seg = g_slice_alloc (WIDGET_SEG_SIZE);
@@ -303,6 +316,7 @@ _gtk_widget_segment_new (GtkTextChildAnchor *anchor)
   g_object_ref (anchor);
   
   return seg;
+#pragma GCC diagnostic pop
 }
 
 void
diff --git a/gtk/gtktextsegment.c b/gtk/gtktextsegment.c
index a202ab603c..aaac2918ba 100644
--- a/gtk/gtktextsegment.c
+++ b/gtk/gtktextsegment.c
@@ -425,6 +425,13 @@ char_segment_check_func (GtkTextLineSegment *segPtr, GtkTextLine *line)
 GtkTextLineSegment*
 _gtk_toggle_segment_new (GtkTextTagInfo *info, gboolean on)
 {
+  /* gcc-11 issues a diagnostic here because the size allocated
+     for SEG does not cover the entire size of a GtkTextLineSegment
+     and gcc has no way to know that the union will only be used
+     for limited types and the additional space is not needed.  */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Warray-bounds"
+
   GtkTextLineSegment *seg;
 
   seg = g_slice_alloc (TSEG_SIZE);
@@ -440,6 +447,7 @@ _gtk_toggle_segment_new (GtkTextTagInfo *info, gboolean on)
   seg->body.toggle.inNodeCounts = 0;
 
   return seg;
+#pragma GCC diagnostic pop
 }
 
 void