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Re: 10 x 1036778084 = ??
- From: Jim Wilson <jim dot wilson at linaro dot org>
- To: Nobby-Hirand <nobby at ntools dot net>, gcc-bugs at gcc dot gnu dot org
- Date: Fri, 8 Jul 2016 15:42:18 -0700
- Subject: Re: 10 x 1036778084 = ??
- Authentication-results: sourceware.org; auth=none
- References: <1467954435905-1279231.post@n5.nabble.com>
On 07/07/2016 10:07 PM, Nobby-Hirand wrote:
I have just find strange answer, 10 x 1036778084 = 1777846248??
Your target has 32-bit integers. The value 1036778084 is close to the
largest representable value. Multiplying by anything larger than 2
causes an overflow, and the result gets truncated. Try using %x to
print hex values to see what is wrong. Or use long long instead of int
to get 64-bit values.
FYI With a more recent gcc version, you can compile with
-fsanitize=undefined and get this:
weathertop:2044$ ./a.out
tmp.c:11:5: runtime error: signed integer overflow: 10 * 1036778084
cannot be represented in type 'int'
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Jim