[PATCH] Fix signed integer overflow in gcc/data-streamer.c

[Markus Trippelsdorf]

Running the testsuite with a -fsanitize=undefined instrumented compiler
shows:
 % gcc -O2 -flto -fno-use-linker-plugin -flto-partition=none 
testsuite/gcc.dg/torture/pr28045.c
gcc/data-streamer.c:113:45: runtime error: negation of -9223372036854775808 
cannot be represented in type 'long int'; cast to an unsigned type to negate 
this value to itself

The fix is obvious.

Boostrapped and tested on x86_64-unknown-linux-gnu.
OK for trunk?
Thanks.

2014-09-28  Markus Trippelsdorf  <mar...@trippelsdorf.de>

        * data-streamer.c (bp_unpack_var_len_int): Avoid signed
        integer overflow.

diff --git a/gcc/data-streamer.c b/gcc/data-streamer.c
index 0e19c72162aa..0760ed590c22 100644
--- a/gcc/data-streamer.c
+++ b/gcc/data-streamer.c
@@ -110,7 +110,7 @@ bp_unpack_var_len_int (struct bitpack_d *bp)
       if ((half_byte & 0x8) == 0)
        {
          if ((shift < HOST_BITS_PER_WIDE_INT) && (half_byte & 0x4))
-           result |= - ((HOST_WIDE_INT)1 << shift);
+           result |= - ((unsigned HOST_WIDE_INT)1 << shift);
 
          return result;
        }
-- 
Markus