Re: Cygwin 64 problem

[Ken Brown <kbrown at cornell dot edu>]

On 11/27/2016 11:02 AM, Ken Brown wrote:
> On 11/27/2016 9:03 AM, Girish Joglekar wrote:
>> Hi Ken,
>> Thank you for your reply on the Cygwin mailing list. I have created a
>> slightly smaller test example smaller than what I had created in Feb.
>> Attached is a tar file. After make insall if you run TEST.x and click
>> the Open button, it gives segmentation fault.
>> Hope you will be able to help.
>> Thank you.
>> Girish
> 
> Please keep the discussion on the mailing list so that people who might
> be able to help will see it.  I personally am not familiar with X11
> programming, so I'm not one of those people.
> 
> I do have a few comments, however:
> 
> 1. This may be slightly smaller than your previous program, but it is
> still *very* far from a small test case.  You really can't expect people
> to debug a program of this size for you.
> 
> 2. I suggest that you build with -Wall (as Marco already suggested in
> the earlier discussion) and fix all the compiler warnings.  I saw
> several that need attention (aside from the many "unused variable"
> warnings).  It wouldn't hurt to also use -Wextra.
> 
> 3. I also suggest that you use gdb to find out where the program is
> crashing and why.  You made a start on that in the discussion last
> March, but you didn't follow through.  (By the way, I recommend building
> without optimization; otherwise you may not be able to get accurate
> information about the crash from gdb.)
> 
> 4. If, after the steps above, you still think the crash is due to a
> Cygwin bug rather than a programming error, then try to extract from
> your program a test case as small as possible that reproduces the crash.

I've looked at this a little, and the crash occurs because of a bad value of a pointer to a font list.  I'm attaching an annotated transcript of a gdb session that illustrates this.  I didn't try to figure out where the bad pointer came from.

As a workaround, you can avoid the crash by removing from mosprshx.c all uses of spreadSheetFont, as in the following patch:

--- mosprshx.c~ 2016-11-27 08:46:12.000000000 -0500
+++ mosprshx.c  2016-11-29 14:58:23.114377500 -0500
@@ -29,8 +29,6 @@
    0x00, 0x7c, 0x07, 0x1e, 0x0f, 0x07, 0x9e, 0x03, 0xfc, 0x01, 0xf8, 0x00,
    0x70, 0x00, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00};
 
-static char *spreadSheetFont = "-adobe-courier-medium-r-normal--12-120-75-75-m-70-iso8859-1";
-
 #ifdef __STDC__
 static void mosprshCreateCheckMarkPixmap(Widget pushButton)
 #else
@@ -208,11 +206,6 @@
    if(isParentManaged)
       XtUnmanageChild(parentFM);
 
-   fromValue.addr = spreadSheetFont;
-   fromValue.size = utStringLength(fromValue.addr) + 1;
-   toValue.addr = NULL;
-   XtConvertAndStore(parentFM,XmRString,&fromValue,XmRFontList,&toValue);
-
    ac = 0;
    XtSetArg(al[ac],XmNuserData,(XtPointer)spreadSheetSize); ac++;
    spreadSheet = XmCreateForm(parentFM,"SpreadSheet",al,ac);
@@ -234,9 +227,6 @@
       XtSetArg(al[ac],XmNtraversalOn,FALSE); ac++;
    }
    XtSetArg(al[ac],XmNcolumns,longestFixedColumnSize+1); ac++;
-   if(toValue.addr) {
-      XtSetArg(al[ac],XmNfontList,*(unsigned int *)toValue.addr); ac++;
-   }
    for(i1=0 ; i1<nRows ; i1++) {
       sprintf(widgetName,"fixedColumnRow%d",i1);
       fixedColumnTF[i1] = XmCreateTextField(fixedColumn,widgetName,al,ac);
@@ -264,9 +254,6 @@
    if(cellSize > 0) {
       XtSetArg(al[ac],XmNcolumns,cellSize); ac++;
    }
-   if(toValue.addr) {
-      XtSetArg(al[ac],XmNfontList,*(unsigned int *)toValue.addr); ac++;
-   }
    for(j1=0 ; j1<nColumns ; j1++) {
       sprintf(widgetName,"fixedRowColumn%d",j1);
       fixedRowTF[j1] = XmCreateTextField(fixedRow,widgetName,al,ac);
@@ -294,9 +281,6 @@
             XtSetArg(al[ac],XmNcolumns,cellSize); ac++;
             XtSetArg(al[ac],XmNmaxLength,cellSize); ac++;
          }
-         if(toValue.addr) {
-            XtSetArg(al[ac],XmNfontList,*(unsigned int *)toValue.addr); ac++;
-         }
          sprintf(widgetName,"column%drow%d",j1,i1);
          variableRowAndColumnTF[loc] = XmCreateTextField(variableColumnFM[j1],widgetName,al,ac); loc++;
       }
@@ -886,15 +870,3 @@
       *nColumns = 0;
    }
 }
-
-
-#ifdef __STDC__
-char *moGetSpreadsheetFont()
-#else
-char *moGetSpreadsheetFont()
-#endif
-{
-   return(spreadSheetFont);
-}
-
-

Ken

Attachment: gdb.txt
Description: Text document

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