pending/1072: Patch for bug 567 (sparc-sun-solaris2.8)

[Duncan Roe <duncanr at optimation dot com dot au>]

>Number:         1072
>Category:       pending
>Synopsis:       Patch for bug 567 (sparc-sun-solaris2.8)
>Confidential:   yes
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          change-request
>Submitter-Id:   unknown
>Arrival-Date:   Wed Feb 19 23:08:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     
>Release:        
>Organization:
>Environment:
>Description:
 --3V7upXqbjpZ4EhLz
 Content-Type: text/plain; charset=us-ascii
 Content-Disposition: inline
 
 Hi,
 
 Bug 567 complains that when you build gdb for sparc-sun-solaris2.8 as a 64-bit
 program, then when you use it to debug a 32-bit program things happen like:
 
    (gdb) p d1
    Cannot access memory at address 0xffbef7a0
    (gdb) x/fg &d1
    0xffbef7a0:     3.2999999999999998
 
 (Actually 567 shows the wrong value being printed to x/fg, but this seems to be
 fixed at gcc-3.2 / gdb 5.2.1).
 
 It turns out that you can't "p" any kind of variable: the problem isn't limited
 to double.
 
 The problem seemed to me that 32-bit negative stack offsets became +ve 64-bit
 quantities. This would give a 33-bit address (the wanted address with an extra
 "1" on the left).
 
 Ideally, I think gdb should just mask off the extra bit when debugging 32-bit
 code. But I couldn't figure out how to do that, so the attached patch
 sign-extends symbol values as they are read in.
 
 GCC 3.2 configuration:
 
  /tmp/gcc-3.2/configure --prefix=/usr/local/gcc-3.2
 
 GDB 5.2.1 configuration
 
  PATH=/usr/local/gcc-3.2/bin:$PATH
  export PATH
  CC="gcc -m64"
  export CC
  CFLAGS="-g -O2"
  export CFLAGS
  ./configure --prefix=/usr/local/solaris2.8_64
 
 You need to put "-m64" in CC rather than CFLAGS else "make install" fails when
 trying to build "chew". This has the unfortunate side-effect that "make check"
 also uses "gcc -m64", i.e. it never exercises "gcc" which would build a 32-bit
 program.
 
 Cheers ... Duncan.
 
 --3V7upXqbjpZ4EhLz
 Content-Type: text/plain; charset=us-ascii
 Content-Description: The patch
 Content-Disposition: attachment; filename="gdb.patch"
 
 diff -r -u gdb-5.2.1.bu/gdb/dbxread.c gdb-5.2.1/gdb/dbxread.c
 --- gdb-5.2.1.bu/gdb/dbxread.c	Fri Apr  5 08:33:49 2002
 +++ gdb-5.2.1/gdb/dbxread.c	Thu Nov 14 16:23:40 2002
 @@ -2591,6 +2591,27 @@
  	fill_symbuf (abfd);
        bufp = &symbuf[symbuf_idx++];
        INTERNALIZE_SYMBOL (nlist, bufp, abfd);
 +
 +      /* ----------------------------------------------- */
 +      /* Horrible fix for when gdb is built with "-m64"  */
 +      /* (sparc-sun-solaris2.8):                         */
 +      /* sign-extend the 32-bit result in nlist.n_value. */
 +      /*                                                 */
 +      /* This fixes the testcase in bug 567,             */
 +      /* in that you can "p d1" successfully.            */
 +      /* Actually you can "p" *anything*                 */
 +      /* (previously, you couldn't).                     */
 +      /*                                                 */
 +      /* I expect this will break something else,        */
 +      /* we'll just have to wait to see what.            */
 +      /*                                                 */
 +      /* The proper fix is for gdb to know that it's     */
 +      /* working on a 32-bit program and                 */
 +      /* truncate addresses to 32 bits before using them */
 +      /* ----------------------------------------------- */
 +      
 +      nlist.n_value = (long)(int)nlist.n_value;
 +      
        OBJSTAT (objfile, n_stabs++);
  
        type = bfd_h_get_8 (abfd, bufp->e_type);
 
 --3V7upXqbjpZ4EhLz
 Content-Type: text/plain; charset=us-ascii
 Content-Description: (simplified) test program from bug 567
 Content-Disposition: attachment; filename="double.c"
 
 /*
  * From GDB bug report 567
 gcc -g -m64 -o double double.c
 gcc -g -o double double.c
  *
  * The report says to breakpoint on the printf line
  * & print the value of d1
  */
 extern int printf(const char *, ...);
 
     int
     main()
     {
         double d1;
 
         d1 = 3.3;
         printf("d1 = %f\n", d1);
 
         return 0;
     }
 
 --3V7upXqbjpZ4EhLz--
 
 
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