Re: unreducable cp_tree_equal ICE in gcc-4.0.0-20050410

[Michael Matz <matz at suse dot de>]

Hi,

On Wed, 13 Apr 2005, Nick Rasmussen wrote:

> I'm running into an ICE in the prerelease, that is proving to be
> very difficult in reducing to a small testcase.  If I preprocess
> the source (via -E or -save-temps) the code successfully compiles.
>  If I minimally change the source file in some ways(like adding a
> static integer in the global scope) the code compiles.  I've been
> able to delete some lines from the source file that's triggering
> the bug, including some from within the function that is
> triggering the ICE, but I'm down to a point where I can't easily
> reduce it further, or even get it into a single source file.

If possible you could tar eveything needed together with a small Makefile, 
for others to look at.  Otherwise it's will be difficult.  You can also 
compile cc1plus with debugging (just do a "make CFLAGS=-g" after 
configuring gcc, no bootstrap), and try to come up with some more info 
yourself.  For instance by printing the two trees which are impossible, by 
going to the cp_tree_equal frame and doing
  (gdb) p debug_tree(t1)
in gdb (and for t2).

> /dept/rnd/vendor/gcc-4.0.0pre1-amd64/bin/g++ -fno-builtin -O2 -g -DHAVE_X86_64 -DHAVE_LITTLE_ENDIAN -DHAVE_BYTESWAP_H -DHAVE_64BIT_POINTER -DHAVE_VA_COPY -DHAVE_XINERAMA -DPLATFORM_LINUX -D_FILE_OFFSET_BITS=64 -DHAVE_STL_LIMITS -DHAVE_IOS_BASE -Drestrict=__restrict__ -DPLATFORM_LINUX_AMD64 -DPLATFORM=LINUX_AMD64 -DBUILD=LINUX_AMD64_GCC400pre1_OPT_DEBUG -DDISTRO_SUSE -DDISTRO=SUSE -DDISTRO_VERSION=91 -DNVIDIA_VERSION_6111 -DNVIDIA_VERSION=6111 -DGCC_VERSION_400pre1 -DNDEBUG -I/usr/share/doc/NVIDIA_GLX-1.0/include -I. -I/dept/rnd/home/nick/work/build-zeno2/SUSE_AMD64_GCC400pre1_OPT_DEBUG/include -I/usr/X11R6/include -c bug.C -o /dev/null
> bug.C: In member function 'void EzFleshMesh::buildNodeArrays()':
> bug.C:411: internal compiler error: in cp_tree_equal, at cp/tree.c:1552

And give the context of that line.  Although it more seems like 
overwriting memory inside the compiler or something like this, as 
otherwise it would be more deterministic.

> #2  0x0000000000473171 in cp_tree_equal (t1=0x2a9a1c94b0, t2=0x2a9a1cbb90) at ../../gcc-4.0.0-20050410/gcc/cp/tree.c:1552
> #3  0x0000000000473198 in cp_tree_equal (t1=0x2a9a013820, t2=0x2a9a031460) at ../../gcc-4.0.0-20050410/gcc/cp/tree.c:1543
> #4  0x00000000004590b3 in comptypes (t1=0x2a9a00ea90, t2=0x2a9a02bdd0, strict=Variable "strict" is not available.
> ) at ../../gcc-4.0.0-20050410/gcc/cp/typeck.c:912
> #5  0x0000000000458ede in comptypes (t1=0x2a9a00ec30, t2=0x2a9a032000, strict=0) at ../../gcc-4.0.0-20050410/gcc/cp/typeck.c:1034
> #6  0x000000000047b0b9 in cxx_types_compatible_p (x=0x2a9a00ec30, y=0x2a9a032000) at ../../gcc-4.0.0-20050410/gcc/cp/cp-objcp-common.c:173
> #7  0x00000000007776bd in expressions_equal_p (e1=0x2a9a1c9640, e2=0x2a9a1cbd20) at ../../gcc-4.0.0-20050410/gcc/tree-vn.c:127
> #8  0x00000000007776f7 in val_expr_pair_expr_eq (p1=0xc16b90, p2=0xcd25e0) at ../../gcc-4.0.0-20050410/gcc/tree-vn.c:153
> #9  0x00000000007ffcba in htab_find_slot_with_hash (htab=0xca98a0, element=0x81c3b9, hash=8504885, insert=INSERT) at ../../gcc-4.0.0-20050410/libiberty/hashtab.c:660
> #10 0x000000000077794f in vn_add (expr=0x2a9a1cbd20, val=0x2a9a240330, vuses=0x0) at ../../gcc-4.0.0-20050410/gcc/tree-vn.c:199
> #11 0x00000000004e09c1 in execute_pre (do_fre=0 '\0') at ../../gcc-4.0.0-20050410/gcc/tree-ssa-pre.c:1742

So PRE is trying to compare two types, and they contains something which 
can't be handled.  Either because they were silently overwritten, or 
because of a logical error.


Ciao,
Michael.