[Bug optimization/13418] New: optimized code calls operator delete before finishing destructor

[stever at eecs dot umich dot edu]

I have a simple object allocator that overrides the class new & delete
operators, and maintains simple bucketed linked lists of freed objects.  This
code has worked with g++ since 1995 or so.  It breaks with optimization on 3.3.1
and 3.3.2 because the code from operator delete that writes the free list
pointer at the head of the object gets executed *before* the object's vtable ptr
is twiddled for the call to the base class's destructor (at least I assume
that's what that store is for).  The free list pointer is clobbered by the
vtable modification, meaning that some subsequent call to operator new treats
the vtable ptr as a pointer to a free memory block, leading eventually to a
segfault.

The attached output is from g++ 3.3.2 on a RH9 machine, though I've seen the bug
also using g++ 3.3.1 on Debian.

output from gcc -v etc.:
------------------------
eading specs from /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3.2/specs
Configured with: /z/stever/gcc-3.3.2/configure --program-suffix=-3.3.2
Thread model: posix
gcc version 3.3.2
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3.2/cc1plus -E -D__GNUG__=3 -quiet
-v -D__GNUC__=3 -D__GNUC_MINOR__=3 -D__GNUC_PATCHLEVEL__=2 -D_GNU_SOURCE
fast_alloc.cc -Wall -O5 fast_alloc.ii
ignoring nonexistent directory "NONE/include"
ignoring nonexistent directory "/usr/local/i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include/c++/3.3.2
 /usr/local/include/c++/3.3.2/i686-pc-linux-gnu
 /usr/local/include/c++/3.3.2/backward
 /usr/local/include
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3.2/include
 /usr/include
End of search list.
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3.2/cc1plus -fpreprocessed
fast_alloc.ii -quiet -dumpbase fast_alloc.cc -auxbase fast_alloc -O5 -Wall
-version -o fast_alloc.s
GNU C++ version 3.3.2 (i686-pc-linux-gnu)
        compiled by GNU C version 3.3.2.
GGC heuristics: --param ggc-min-expand=98 --param ggc-min-heapsize=128721
 as -V -Qy -o fast_alloc.o fast_alloc.s
GNU assembler version 2.13.90.0.18 (i386-redhat-linux) using BFD version
2.13.90.0.18 20030206
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3.2/collect2 --eh-frame-hdr -m
elf_i386 -dynamic-linker /lib/ld-linux.so.2 /usr/lib/crt1.o /usr/lib/crti.o
/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3.2/crtbegin.o
-L/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3.2
-L/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3.2/../../.. fast_alloc.o -lstdc++
-lm -lgcc_s -lgcc -lc -lgcc_s -lgcc
/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.3.2/crtend.o /usr/lib/crtn.o

-- 
           Summary: optimized code calls operator delete before finishing
                    destructor
           Product: gcc
           Version: 3.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: stever at eecs dot umich dot edu
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13418