[Bug c/53968] New: integer undefined behaviors in GCC

[Bug c/53968] New: integer undefined behaviors in GCC

[regehr at cs dot utah.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53968

             Bug #: 53968
           Summary: integer undefined behaviors in GCC
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: regehr@cs.utah.edu


Using IOC (link below) I made a GCC that looks for integer overflow problems in
itself, and then used it to run the GCC testsuite and bootstrap itself. The
resulting defects are listed below.

I've found that the best way to track down these problems is to put an
assertion into the source code close to where the overflow happens.

Note that this is far fewer undefined behaviors than were present two years
ago:

  http://gcc.gnu.org/ml/gcc/2010-08/msg00039.html

Version info:

regehr@home:~/z/checked-gcc-install/bin$ ./gcc -v
Using built-in specs.
COLLECT_GCC=./gcc
COLLECT_LTO_WRAPPER=/home/regehr/z/checked-gcc-install/libexec/gcc/x86_64-unknown-linux-gnu/4.8.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /home/regehr/z/compiler-source/gcc/configure
--enable-languages=c,c++ CC='clang -w -fcatch-undefined-behavior' CXX='clang++
-w -fcatch-undefined-behavior' --prefix=/home/regehr/z/checked-gcc-install
--disable-bootstrap
Thread model: posix
gcc version 4.8.0 20120714 (experimental) (GCC) 

IOC tool:

http://embed.cs.utah.edu/ioc/

Defects:

ARITHMETIC UNDEFINED at </home/regehr/z/compiler-source/gcc/gcc/diagnostic.c,
(244:28)> : Op: -, Reason : Signed Subtraction Overflow, BINARY OPERATION: left
(int32): 2147483647 right (int32): -1 

ARITHMETIC UNDEFINED at </home/regehr/z/compiler-source/gcc/gcc/double-int.c,
(158:21)> : Op: *, Reason : Signed Multiplication Overflow, BINARY OPERATION:
left (int64): 4294967295 right (int64): 4294967295 

ARITHMETIC UNDEFINED at </home/regehr/z/compiler-source/gcc/gcc/double-int.c,
(613:46)> : Op: <<, Reason : Unsigned Left Shift: Right operand is negative or
is greater than or equal to the width of the promoted left operand, BINARY
OPERATION: left (uint64): 2 right (uint64): 4294967295 

ARITHMETIC UNDEFINED at </home/regehr/z/compiler-source/gcc/gcc/expr.c,
(3832:20)> : Op: -, Reason : Signed Subtraction Overflow, UNARY OPERATION: left
(int64): 0 right (int64): -9223372036854775808 

ARITHMETIC UNDEFINED at
</home/regehr/z/compiler-source/gcc/gcc/ipa-inline-analysis.c, (2347:22)> : Op:
*, Reason : Signed Multiplication Overflow, BINARY OPERATION: left (int32):
256348 right (int32): 10000 

ARITHMETIC UNDEFINED at </home/regehr/z/compiler-source/gcc/gcc/simplify-rtx.c,
(69:24)> : Op: -, Reason : Signed Subtraction Overflow, UNARY OPERATION: left
(int64): 0 right (int64): -9223372036854775808 

ARITHMETIC UNDEFINED at </home/regehr/z/compiler-source/gcc/gcc/stor-layout.c,
(2563:52)> : Op: -, Reason : Signed Subtraction Overflow, BINARY OPERATION:
left (int64): -9223372036854775808 right (int64): 1 

ARITHMETIC UNDEFINED at </home/regehr/z/compiler-source/gcc/gcc/stor-layout.c,
(2566:54)> : Op: -, Reason : Signed Subtraction Overflow, BINARY OPERATION:
left (int64): -9223372036854775808 right (int64): 1 

ARITHMETIC UNDEFINED at
</home/regehr/z/compiler-source/gcc/gcc/tree-ssa-loop-ivopts.c, (3450:10)> :
Op: -, Reason : Signed Subtraction Overflow, UNARY OPERATION: left (int64): 0
right (int64): -9223372036854775808 

ARITHMETIC UNDEFINED at
</home/regehr/z/compiler-source/gcc/gcc/tree-ssa-loop-ivopts.c, (3459:35)> :
Op: -, Reason : Signed Subtraction Overflow, BINARY OPERATION: left (int64):
-9223372036854775808 right (int64): 1 

ARITHMETIC UNDEFINED at </home/regehr/z/compiler-source/gcc/gcc/tree.c,
(1889:37)> : Op: -, Reason : Signed Subtraction Overflow, BINARY OPERATION:
left (int64): -9223372036854775808 right (int64): 1

[Bug c/53968] integer undefined behaviors in GCC

[regehr at cs dot utah.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53968

--- Comment #1 from John Regehr <regehr at cs dot utah.edu> 2012-07-14 22:53:06 UTC ---
Also there are about 50 defects relating to C99's restrictive rules for
left-shifts of signed integers.  I have omitted them since people typically
don't care to fix these.  If anyone wants to see them, let me know.

[Bug c/53968] integer undefined behaviors in GCC

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53968

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-08-13 12:40:04 UTC ---
Author: jakub
Date: Mon Aug 13 12:39:54 2012
New Revision: 190342

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=190342
Log:
    PR c/53968
    * tree.c (integer_pow2p): Avoid undefined signed overflows.
    * simplify-rtx.c (neg_const_int): Likewise.
    * expr.c (fixup_args_size_notes): Likewise.
    * stor-layout.c (set_min_and_max_values_for_integral_type): Likewise.
    * double-int.c (mul_double_wide_with_sign): Likewise.
    (double_int_mask): Likewise.
    * tree-ssa-loop-ivopts.c (get_address_cost): Likewise.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/double-int.c
    trunk/gcc/expr.c
    trunk/gcc/simplify-rtx.c
    trunk/gcc/stor-layout.c
    trunk/gcc/tree-ssa-loop-ivopts.c
    trunk/gcc/tree.c

[Bug c/53968] integer undefined behaviors in GCC

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53968

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-08-13
                 CC|                            |hubicka at gcc dot gnu.org,
                   |                            |jakub at gcc dot gnu.org
     Ever Confirmed|0                           |1

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-08-13 12:41:06 UTC ---
Haven't reproduced the diagnostic.c failure, and leaving the ipa hunk to Honza.

[Bug c/53968] integer undefined behaviors in GCC

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53968

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |mpolacek at gcc dot gnu.org
         Resolution|---                         |FIXED

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Should be fixed.