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

Markus Trippelsdorf markus@trippelsdorf.de
Sun Sep 28 12:22:00 GMT 2014


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  <markus@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



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