[Bug c/15400] New: gcc accumulates instead of overlaying automatic variables

[Bug c/15400] New: gcc accumulates instead of overlaying automatic variables

[leblanc at skycomputers dot com]

See the source down below.  SUN and Metaware believe, correctly, that the
two blocks overlay each other in the final stack frame.  GCC adds them
together.  It looks like this mistake has been around for quite a while.

(1) on Solaris

    SUN
        % /opt/SUNWspro/bin/cc -V
        cc: Sun WorkShop 6 2000/04/07 C 5.1

        % /opt/SUNWspro/bin/cc x.c f.c
        x.c:
        f.c:

        % ./a.out
        frame is about 612 bytes
        frame is about 612 bytes

    HighC
        % hc x.c f.c -Hcopyr
        x.c:
        MetaWare High C Compiler R2.8   Serial 1-SKY-799999.
        (c) Copyright 1987-98, MetaWare Incorporated
        f.c:
        w "f.c",L4/C3(#291):    printf: Function called but not declared.
        No errors   1 warning

        % ./a.out
        frame is about 608 bytes
        frame is about 608 bytes

    GCC
        % gcc -v
        Reading specs from /usr/local/lib/gcc-lib/sparc-sun-solaris2.8/2.95.3/specs
        gcc version 2.95.3 20010315 (release)

        % gcc x.c f.c

        % ./a.out
        frame is about 1136 bytes
        frame is about 624 bytes

(2) on YDL 3.0

        $ gcc -v
        ...
        gcc version 3.3

        $ gcc x.c f.c

        $ ./a.out
        frame is about 547 bytes
        frame is about 1059 bytes

SOURCE

        % cat f.c
        void foo(char *p)
        {
          char x;
          printf("frame is about %d bytes\n",p-&x);
        }

        % cat x.c

        #define N 512

        extern void foo(char *p);

        int main()
        {
          {
            char x[N];
            foo(&x[N-1]);
          }
          {
            char x[N];
            foo(&x[N-1]);
          }
          return 0;
        }

-- 
           Summary: gcc accumulates instead of overlaying automatic
                    variables
           Product: gcc
           Version: 3.3
            Status: UNCONFIRMED
          Severity: critical
          Priority: P1
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: leblanc at skycomputers dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: ppc-*-linux
  GCC host triplet: ppc-*-linux
GCC target triplet: ppc-*-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15400

[Bug c/15400] gcc accumulates instead of overlaying automatic variables

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-12 17:33 -------
This is not a bug per say really but it is bug 9997 anyways so closing as a dup.

*** This bug has been marked as a duplicate of 9997 ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15400