locale: Fix localedata/sort-test undefined behavior
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| Context |
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Description |
| dj/TryBot-apply_patch |
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Patch applied to master at the time it was sent
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| dj/TryBot-32bit |
success
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Build for i686
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Commit Message
The collate-test.c triggers UB with an signed integer overflow,
which results in an error on some architectures (powerpc32).
Checked on x86_64, i686, and powerpc.
---
localedata/collate-test.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
Comments
On Nov 03 2021, Adhemerval Zanella wrote:
> The collate-test.c triggers UB with an signed integer overflow,
> which results in an error on some architectures (powerpc32).
>
> Checked on x86_64, i686, and powerpc.
> ---
> localedata/collate-test.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/localedata/collate-test.c b/localedata/collate-test.c
> index 46b91ec57f..09fd5158a7 100644
> --- a/localedata/collate-test.c
> +++ b/localedata/collate-test.c
> @@ -86,7 +86,7 @@ main (int argc, char *argv[])
> srandom (atoi (argv[1]));
> for (n = 0; n < 10 * nstrings; ++n)
> {
> - int r1, r2, r;
> + int r1, r2;
> size_t idx1 = random () % nstrings;
> size_t idx2 = random () % nstrings;
> struct lines tmp = strings[idx1];
> @@ -96,9 +96,10 @@ main (int argc, char *argv[])
> /* While we are at it a first little test. */
> r1 = strcoll (strings[idx1].key, strings[idx2].key);
> r2 = strcoll (strings[idx2].key, strings[idx1].key);
> - r = r1 * r2;
>
> - if (r > 0 || (r == 0 && r1 != 0) || (r == 0 && r2 != 0))
> + if ((r1 > 0 && r2 > 0)
That doesn't look the same. Shouldn't that be (r1 > 0) == (r2 > 0)?
Andreas.
On 11/3/21 12:50, Andreas Schwab wrote:
>> - if (r > 0 || (r == 0 && r1 != 0) || (r == 0 && r2 != 0))
>> + if ((r1 > 0 && r2 > 0)
> That doesn't look the same. Shouldn't that be (r1 > 0) == (r2 > 0)?
But that would be true when r1 == 0 && r2 == 0, whereas the original
expression (if there's no overflow) would make it false.
On 11/3/21 12:40, Adhemerval Zanella via Libc-alpha wrote:
> - r = r1 * r2;
>
> - if (r > 0 || (r == 0 && r1 != 0) || (r == 0 && r2 != 0))
> + if ((r1 > 0 && r2 > 0)
> + || ((r1 == 0 || r2 == 0) && r1 != 0)
> + || ((r1 == 0 || r2 == 0) && r2 != 0))
This is both too-complicated and (as Andreas wrote) not quite right.
Instead, I suggest something like this:
if (signum (r1) != - signum (r2))
where 'signum' is defined by something like this:
static int signum (int n) { return (0 < n) - (n < 0); }
This is clearer and avoids the overflow bug.
@@ -86,7 +86,7 @@ main (int argc, char *argv[])
srandom (atoi (argv[1]));
for (n = 0; n < 10 * nstrings; ++n)
{
- int r1, r2, r;
+ int r1, r2;
size_t idx1 = random () % nstrings;
size_t idx2 = random () % nstrings;
struct lines tmp = strings[idx1];
@@ -96,9 +96,10 @@ main (int argc, char *argv[])
/* While we are at it a first little test. */
r1 = strcoll (strings[idx1].key, strings[idx2].key);
r2 = strcoll (strings[idx2].key, strings[idx1].key);
- r = r1 * r2;
- if (r > 0 || (r == 0 && r1 != 0) || (r == 0 && r2 != 0))
+ if ((r1 > 0 && r2 > 0)
+ || ((r1 == 0 || r2 == 0) && r1 != 0)
+ || ((r1 == 0 || r2 == 0) && r2 != 0))
printf ("`%s' and `%s' collate wrong: %d vs. %d\n",
strings[idx1].key, strings[idx2].key, r1, r2);
}