Bug 81509 – [Qt] fast/table/max-width-integer-overflow.html differs on 32- and 64-bit systems

• Status: RESOLVED
• Resolution: INVALID
• Component: Tools / Tests

[János Badics]

From revision #111156 32-bit and 64-bit QtWebKit versions give different results on fast/table/max-width-integer-overflow-expected.html

Thist test should be put on the skipped list since there is no solution for both the 32-bit and 64-bit versions to give the same results.

[János Badics]

The expected.txt in r111156 works fine on 32-bit systems.
But on 64-bit systems some modifications should be made to work well:

diff --git a/LayoutTests/platform/qt/fast/table/max-width-integer-overflow-expected.txt b/LayoutTests/platform/qt/fast/table/max-width-integer-overflow-expected.txt
index 9171655..392ec4c 100644
--- a/LayoutTests/platform/qt/fast/table/max-width-integer-overflow-expected.txt
+++ b/LayoutTests/platform/qt/fast/table/max-width-integer-overflow-expected.txt
@@ -6,16 +6,16 @@ layer at (0,0) size 800x600
       RenderTable {TABLE} at (0,0) size 780x24 [bgcolor=#FF0000]
         RenderTableSection {TBODY} at (0,0) size 780x24
           RenderTableRow {TR} at (0,0) size 780x24
-            RenderTableCell {TD} at (0,0) size 770x24 [r=0 c=0 rs=1 cs=1]
-              RenderTable {TABLE} at (0,0) size 770x24
-                RenderTableSection {TBODY} at (0,0) size 770x24
-                  RenderTableRow {TR} at (0,0) size 770x24
-                    RenderTableCell {TD} at (0,0) size 770x24 [r=0 c=0 rs=1 cs=1]
-                      RenderBlock {DIV} at (0,0) size 770x24
-                        RenderTable {TABLE} at (0,0) size 770x24 [bgcolor=#008000]
-                          RenderTableSection {TBODY} at (0,0) size 770x24
-                            RenderTableRow {TR} at (0,2) size 770x20
-                              RenderTableCell {TD} at (2,11) size 762x2 [r=0 c=0 rs=1 cs=1]
-                              RenderTableCell {TD} at (766,11) size 2x2 [r=0 c=1 rs=1 cs=1]
-            RenderTableCell {TD} at (770,0) size 10x24 [r=0 c=1 rs=1 cs=1]
+            RenderTableCell {TD} at (0,0) size 780x24 [r=0 c=0 rs=1 cs=1]
+              RenderTable {TABLE} at (0,0) size 780x24
+                RenderTableSection {TBODY} at (0,0) size 780x24
+                  RenderTableRow {TR} at (0,0) size 780x24
+                    RenderTableCell {TD} at (0,0) size 780x24 [r=0 c=0 rs=1 cs=1]
+                      RenderBlock {DIV} at (0,0) size 780x24
+                        RenderTable {TABLE} at (0,0) size 780x24 [bgcolor=#008000]
+                          RenderTableSection {TBODY} at (0,0) size 780x24
+                            RenderTableRow {TR} at (0,2) size 780x20
+                              RenderTableCell {TD} at (2,11) size 772x2 [r=0 c=0 rs=1 cs=1]
+                              RenderTableCell {TD} at (776,11) size 2x2 [r=0 c=1 rs=1 cs=1]
+            RenderTableCell {TD} at (780,0) size 10x24 [r=0 c=1 rs=1 cs=1]
               RenderBlock {DIV} at (0,0) size 10x24 [bgcolor=#008000]

[János Badics]

Created attachment 132585 [details]
proposed patch

[WebKit Review Bot]

Attachment 132585 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'LayoutTests/ChangeLog', u'LayoutTests/plat..." exit_code: 1
LayoutTests/ChangeLog:1:  ChangeLog entry has no bug number  [changelog/bugnumber] [5]
Total errors found: 1 in 2 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Csaba Osztrogonác]

Comment on attachment 132585 [details]
proposed patch

Skip landed in http://trac.webkit.org/changeset/111363

[Csaba Osztrogonác]

(In reply to comment #1)
> The expected.txt in r111156 works fine on 32-bit systems.
> But on 64-bit systems some modifications should be made to work well:

Before r111156, it passed on 32 bit and 64 bit too. After r111156, it passes 
on 32 bit, but fails on 64 bit. If we do the same change on Qt as you did
on Mac by r111156, it will make the test pass on 64 bit, and fail on 32 bit.
 
> diff --git a/LayoutTests/platform/qt/fast/table/max-width-integer-overflow-expected.txt b/LayoutTests/platform/qt/fast/table/max-width-integer-overflow-expected.txt

--- : correct expected result on 32 bit always, and on 64 bit before r111156
+++ : correct expected result on 64 bit after r111156

[Csaba Osztrogonác]

Any idea? Maybe you can reproduce it on other 32/64 bit platforms too.

[Luke Macpherson]

Just to make sure we understand what's going on, we used to clamp Lengths to 2^28 bits. Lengths themselves have supported the full range of int (and also float) lengths for a while, but we were artificially clamping some values to 2^28 anyway. https://bugs.webkit.org/show_bug.cgi?id=67976 removed that clamping, so the full range of values supported by Length can be used.

If you're seeing different values on 32 and 64 bit systems, that must mean that sizeof(int) is different on those systems - which is surprising to me, since a lot of webkit code seems to assume that sizeof(int)==4 (or at least ==sizeof(float)) for data structure packing.

In any case, I don't think it's a bug, at least insofar as the range of lengths is not defined by the CSS spec.

[Jocelyn Turcotte]

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