c/8960: [3.2/3.3 regression] Segfault with __attribute__ ((mode (...))) in start_function:5702

[Christian Ehrhardt <ehrhardt at mathematik dot uni-ulm dot de>]

>Number:         8960
>Category:       c
>Synopsis:       [3.2/3.3 regression] Segfault with __attribute__ ((mode (...))) in start_function:5702
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          ice-on-legal-code
>Submitter-Id:   net
>Arrival-Date:   Mon Dec 16 06:36:04 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     Christian Ehrhardt
>Release:        3.2.2, 3.3
>Organization:
>Environment:
Mostly arch and version independant, but tested with this:

Reading specs from gcc-install/bin/../lib/gcc-lib/sparc-sun-solaris2.9/3.3/specs
Configured with: /home/thales/ehrhardt/gcc-cvs/gcc/configure --with-ld=/usr/local/bin/ld --with-as=/usr/local/bin/as --with-gnu-as --with-gnu-ld --enable-languages=c,c++ : (reconfigured) /home/thales/ehrhardt/gcc-cvs/gcc/configure --with-ld=/usr/local/bin/ld --with-as=/usr/local/bin/as --with-gnu-as --with-gnu-ld --enable-languages=c,c++ --prefix=/home/thales/ehrhardt/gcc-install/
Thread model: posix
gcc version 3.3 20021204 (experimental)
SunOS theseus 5.9 Generic_112233-02 sun4u sparc SUNW,Ultra-4
>Description:
This  piece of code ICEs on virtually any 3.2 or 3.3 compiler and
on both sun-sparc-solaris and i386.
--------------------- cut --------------------
__attribute__ ((mode (SI)))
int f () { }
--------------------- cut --------------------

x.c:2: internal compiler error: Segmentation Fault
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://www.gnu.org/software/gcc/bugs.html> for instructions.

The segfault is in this piece of code in start_function:

  if (!COMPLETE_OR_VOID_TYPE_P (TREE_TYPE (TREE_TYPE (decl1))))
    { 
      error ("return type is an incomplete type");
      /* Make it return void instead.  */
      TREE_TYPE (decl1)
        = build_function_type (void_type_node,
                               TYPE_ARG_TYPES (TREE_TYPE (decl1)));
    }

The real problem seems to be when applying attributs. gdb shows that
the following happens in start_function:

grokdeclarator creates a proper function declaration with return type int
in decl1. Afterwards decl_attributes is called to apply the mode attribute
to the function declaration. decl_attributes properly detects that the
mode attribute doesn't apply to a declaration but a type. The mistake is
that the attribute is then applied to the function type. This will
replace the function type with an SImode integer type.
Thus f becomes a function declaration with a type "int" instead of
"function returning int". This results in an ICE a few instructions
later.

     regards   Christian

>How-To-Repeat:
See description. Just compile the sample code with any 3.x compiler.
2.95.3 is fine.
>Fix:
Using a typedef for the return type fixes the ice but be aware that there
is another probably unrelated bug (PR 7227) which is about bad code
generation with some modes.
>Release-Note:
>Audit-Trail:
>Unformatted: