[Bug c++/51264] New: O0 Bootstrap failure: control reaches end of non-void function

[Bug c++/51264] New: O0 Bootstrap failure: control reaches end of non-void function

[vries at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51264

             Bug #: 51264
           Summary: O0 Bootstrap failure: control reaches end of non-void
                    function
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: vries@gcc.gnu.org


This might be a duplicate of PR20681, but I'm filing it just in case it's not.

During a x86-64 -O0 bootstrap, the 3rd stage fails with:
...
In function 'hashval_t iterative_hash_expr(const_tree, hashval_t)':
/scratch/vries/b2/ref-x86_64-ml-11-11-21/src/gcc-mainline/gcc/tree.c:6999:1:
error: control reaches end of non-void function [-Werror=return-type]
cc1plus: all warnings being treated as errors
...

full command line:
...
/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/gcc-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/./prev-gcc/g++
-B/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/gcc-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/./prev-gcc/
-B/opt/codesourcery/x86_64-unknown-linux-gnu/bin/ -nostdinc++
-B/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/gcc-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/prev-x86_64-unknown-linux-gnu/libstdc++-v3/src/.libs
-B/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/gcc-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/prev-x86_64-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs
-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/gcc-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/prev-x86_64-unknown-linux-gnu/libstdc++-v3/include/x86_64-unknown-linux-gnu
-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/gcc-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/prev-x86_64-unknown-linux-gnu/libstdc++-v3/include
-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/src/gcc-mainline/libstdc++-v3/libsupc++
-L/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/gcc-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/prev-x86_64-unknown-linux-gnu/libstdc++-v3/src/.libs
-L/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/gcc-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/prev-x86_64-unknown-linux-gnu/libstdc++-v3/libsupc++/.libs
-c   -g -O0 -gtoggle -DIN_GCC   -fno-exceptions -fno-rtti -W -Wall
-Wno-narrowing -Wwrite-strings -Wcast-qual -Wmissing-format-attribute -pedantic
-Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Werror -fno-common
 -DHAVE_CONFIG_H -I. -I.
-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/src/gcc-mainline/gcc
-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/src/gcc-mainline/gcc/.
-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/src/gcc-mainline/gcc/../include
-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/src/gcc-mainline/gcc/../libcpp/include
-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/host-libs-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/usr/include
-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/host-libs-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/usr/include
-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/host-libs-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/usr/include

-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/src/gcc-mainline/gcc/../libdecnumber
-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/src/gcc-mainline/gcc/../libdecnumber/bid
-I../libdecnumber
-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/host-libs-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/usr/include

-I/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/host-libs-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/usr/include
 /scratch/vries/b2/ref-x86_64-ml-11-11-21/src/gcc-mainline/gcc/tree.c -o
tree.o/scratch/vries/b2/ref-x86_64-ml-11-11-21/src/gcc-mainline/gcc/tree.c: In
function 'hashval_t iterative_hash_expr(const_tree, hashval_t)':
/scratch/vries/b2/ref-x86_64-ml-11-11-21/src/gcc-mainline/gcc/tree.c:6999:1:
error: control reaches end of non-void function [-Werror=return-type]
cc1plus: all warnings being treated as errors
...

configure line:
...
Configured with:
/scratch/vries/b2/ref-x86_64-ml-11-11-21/src/gcc-mainline/configure
--build=x86_64-unknown-linux-gnu --host=x86_64-unknown-linux-gnu
--target=x86_64-unknown-linux-gnu --enable-threads --disable-libmudflap
--disable-libssp --disable-libstdcxx-pch --enable-checking=yes,rtl
--disable-multilib --with-gnu-as --with-gnu-ld --enable-languages=c,c++
--enable-shared --enable-lto --disable-nls --prefix=/opt/codesourcery
--with-gmp=/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/host-libs-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/usr
--with-mpfr=/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/host-libs-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/usr
--with-mpc=/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/host-libs-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/usr
--with-ppl=/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/host-libs-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/usr
--with-host-libstdcxx='-L/usr/local/tools/gcc-4.3.3/lib64 -static-libgcc
-Wl,-Bstatic,-lstdc++,-Bdynamic -lm'
--with-cloog=/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/host-libs-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/usr
--with-libelf=/scratch/vries/b2/ref-x86_64-ml-11-11-21/obj/host-libs-mainline-0-x86_64-unknown-linux-gnu-x86_64-unknown-linux-gnu/usr
--disable-libgomp
--with-build-time-tools=/scratch/vries/b2/ref-x86_64-ml-11-11-21/install/x86_64-unknown-linux-gnu/bin
--with-build-time-tools=/scratch/vries/b2/ref-x86_64-ml-11-11-21/install/x86_64-unknown-linux-gnu/bin
...

I hit the problem with r181586.

[Bug c++/51264] O0 Bootstrap failure: control reaches end of non-void function

[vries at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51264

--- Comment #1 from vries at gcc dot gnu.org 2011-11-22 01:38:07 UTC ---
Minimal example tree.cc:
...
extern void iterative_hash (const int *);

unsigned int
iterative_hash_expr (unsigned int val)
{
  int code;
  switch (val)
    {
    default:
      iterative_hash (&code);
      return 0;
      break;
    }
}
...

to reproduce:
...
gcc -Werror -Wreturn-type -O0 tree.cc -S -fno-exceptions
...

[Bug c++/51264] O0 Bootstrap failure: control reaches end of non-void function

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51264

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-11-22 01:47:58 UTC ---
(In reply to comment #0)
> This might be a duplicate of PR20681, but I'm filing it just in case it's not.


It is.  I had some patches which improve the situation here but I lost them
over the years.  Though I think I might have posted some of them already.

[Bug c++/51264] O0 Bootstrap failure: control reaches end of non-void function

[vries at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51264

vries at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |matz at suse dot de

--- Comment #3 from vries at gcc dot gnu.org 2011-11-22 02:38:30 UTC ---
Triggered/caused by r181172:
...
r181172 | matz | 2011-11-08 17:47:16 +0100 (Tue, 08 Nov 2011) | 44 lines

    * gengtype.c (write_field_root): Avoid out-of-scope access of newv.

    * tree-stdarg.c (execute_optimize_stdarg): Accept clobbers.

    * tree.h (TREE_CLOBBER_P): New macro.
    * gimple.h (gimple_clobber_p): New inline function.
    * gimplify.c (gimplify_bind_expr): Add clobbers for all variables
    that go out of scope and live in memory.
    * tree-ssa-operands.c (get_expr_operands): Transfer volatility also
    for constructors.
    * cfgexpand.c (decl_to_stack_part): New static variable.
    (add_stack_var): Allocate it, and remember mapping.
    (fini_vars_expansion): Deallocate it.
    (stack_var_conflict_p): Add early outs.
    (visit_op, visit_conflict, add_scope_conflicts_1,
    add_scope_conflicts): New static functions.
    (expand_used_vars_for_block): Don't call add_stack_var_conflict, tidy.
    (expand_used_vars): Add scope conflicts.
    (expand_gimple_stmt_1): Expand clobbers to nothing.
    (expand_debug_expr): Ditto.

    * tree-pretty-print.c (dump_generic_node): Dump clobbers nicely.
    * tree-ssa-live.c (remove_unused_locals): Remove clobbers that
    refer to otherwise unused locals.
    * tree-sra.c (build_accesses_from_assign): Ignore clobbers.
    * tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Clobbers of
    SSA names aren't necessary.
    (propagate_necessity): Accept and ignore constructors on the rhs,
    tidy.
    * gimple.c (walk_gimple_op): Accept constructors like mem_rhs.
    * tree-ssa-structalias.c (find_func_aliases): Clobbers don't store
    any known value.
    * tree-ssa-sccvn.c (vn_reference_lookup_3): Ditto, in particular they
    don't zero-initialize something.
    * tree-ssa-phiopt.c (cond_if_else_store_replacement_1): Ignore
    clobber RHS, we don't want PHI nodes with those.
...

[Bug c++/51264] O0 Bootstrap failure: control reaches end of non-void function

[vries at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51264

--- Comment #4 from vries at gcc dot gnu.org 2011-11-22 02:52:20 UTC ---
dumps start diverging at tree.cc.004t.gimple: 
...
r181171                              |  r181172
unsigned int iterative_hash_expr(un     unsigned int iterative_hash_expr(un
{                                       {
  unsigned int D.2185;                    unsigned int D.2185;
  int code;                               int code;

  switch (val) <default: <D.2182>>   |    try
  <D.2182>:                          |      {
  iterative_hash (&code);            |        switch (val) <default: <D.218
  D.2185 = 0;                        |        <D.2182>:
  return D.2185;                     |        iterative_hash (&code);
  goto <D.2184>;                     |        D.2185 = 0;
  <D.2184>:                          |        return D.2185;
                                     >        goto <D.2184>;
                                     >        <D.2184>:
                                     >      }
                                     >    finally
                                     >      {
                                     >        code = {CLOBBER};
                                     >      }
}                                       }
...

[Bug c++/51264] O0 Bootstrap failure: control reaches end of non-void function

[vries at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51264

--- Comment #5 from vries at gcc dot gnu.org 2011-11-22 02:57:45 UTC ---
Difference in dumps just before error in r181172, at tree.cc.014t.cfg:
...
r181171                              |  r181172
unsigned int iterative_hash_expr(un     unsigned int iterative_hash_expr(un
{                                       {
                                     >    int finally_tmp.0;
  int code;                               int code;
  unsigned int D.2185;                    unsigned int D.2185;

<bb 2>:                                 <bb 2>:
  iterative_hash (&code);                 iterative_hash (&code);
  D.2185 = 0;                             D.2185 = 0;
                                     >    finally_tmp.0 = 0;
                                     >    code = {CLOBBER};
                                     >    switch (finally_tmp.0)
                                     >      <default: <L6>,
                                     >       case 1: <L7>>

<L2>:                                |  <L7>:
                                     >    return;
                                     >
                                     >  <L6>:
  return D.2185;                          return D.2185;

}                                       }
...

[Bug c++/51264] O0 Bootstrap failure: control reaches end of non-void function

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51264

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-11-22 03:03:37 UTC ---
Hmm, I don't think we need a clobber for the outer most scope of the function
really.  Though that might only allow us to get the bootstrap to work better
and might improve code generation.

[Bug c++/51264] O0 Bootstrap failure: control reaches end of non-void function

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51264

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-11-22 03:44:39 UTC ---
Created attachment 25877
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=25877
Patch which improves the use of clobbers for toplevel BIND expressions.

Though at -O0 we should not emit the clobbers at all.  That can be cured by
adding !optimize to the condition which includes !top_level.

[Bug c++/51264] O0 Bootstrap failure: control reaches end of non-void function

[matz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51264

Michael Matz <matz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |matz at gcc dot gnu.org

--- Comment #8 from Michael Matz <matz at gcc dot gnu.org> 2011-11-22 12:59:59 UTC ---
Andrew: no, the clobbers are needed also for the outer bind, in order to make
inlining such functions just work (i.e. enable stack sharing between different
inlined functions).  Otherwise we'd have to add the clobbers in the inliner
which is more difficult because the try/finally are already lowered.

In this case it's clearly a problem in tree.c, just remove the superfluous
break.

[Bug c++/51264] O0 Bootstrap failure: control reaches end of non-void function

[matz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51264

--- Comment #9 from Michael Matz <matz at gcc dot gnu.org> 2011-11-22 13:32:20 UTC ---
Author: matz
Date: Tue Nov 22 13:32:15 2011
New Revision: 181615

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=181615
Log:
    PR c++/51264
    * tree.c (iterative_hash_expr): Remove break after return.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/tree.c

[Bug c++/51264] O0 Bootstrap failure: control reaches end of non-void function

[matz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51264

--- Comment #10 from Michael Matz <matz at gcc dot gnu.org> 2011-11-22 14:18:35 UTC ---
Fixed.  Improving the situation with the clobbers should be tracked somewhere
else.

[Bug c++/51264] O0 Bootstrap failure: control reaches end of non-void function

[matz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51264

Michael Matz <matz at gcc dot gnu.org> changed:

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

--- Comment #11 from Michael Matz <matz at gcc dot gnu.org> 2011-11-22 14:19:17 UTC ---
.