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author | Mark H Weaver <mhw@netris.org> | 2014-03-11 20:19:17 -0400 |
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committer | Mark H Weaver <mhw@netris.org> | 2014-03-11 21:39:13 -0400 |
commit | 03cce0ce5fba210e4abd8fa5dfddb04022a27e75 (patch) | |
tree | 4fb231f8147a10969d1cf4b037cf999364a44d22 /libguile/vm-i-scheme.c | |
parent | 5fbf0e0f99431f54da032bda47d8125f9d34b4b1 (diff) | |
download | guile-03cce0ce5fba210e4abd8fa5dfddb04022a27e75.tar.gz |
Avoid undefined behavior regarding signed integers and left shifts.
* libguile/numbers.c (scm_logbit_p): If the requested bit is the sign
bit (or above), check the sign portably. Otherwise, ensure that we're
testing the bit in a two's complement representation.
(left_shift_exact_integer): Avoid left-shifting negative integers.
* libguile/vm-i-scheme.c (ash): Avoid left-shifting negative integers.
Diffstat (limited to 'libguile/vm-i-scheme.c')
-rw-r--r-- | libguile/vm-i-scheme.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/libguile/vm-i-scheme.c b/libguile/vm-i-scheme.c index dd2150ddc..587aa9566 100644 --- a/libguile/vm-i-scheme.c +++ b/libguile/vm-i-scheme.c @@ -1,4 +1,5 @@ -/* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc. +/* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013, + * 2014 Free Software Foundation, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public License @@ -505,7 +506,9 @@ VM_DEFINE_FUNCTION (159, ash, "ash", 2) && ((scm_t_bits) (SCM_SRS (nn, (SCM_I_FIXNUM_BIT-1 - bits_to_shift)) + 1) <= 1)) - RETURN (SCM_I_MAKINUM (nn << bits_to_shift)); + RETURN (SCM_I_MAKINUM (nn < 0 + ? -(-nn << bits_to_shift) + : (nn << bits_to_shift))); /* fall through */ } /* fall through */ |