Messages in this thread | | | From | Linus Torvalds <> | Date | Tue, 11 Dec 2018 10:19:08 -0800 | Subject | Re: [PATCH 2/2] vsprintf: Stop using obsolete simple_strtoul() |
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On Tue, Dec 11, 2018 at 10:05 AM Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > > I think it's slightly more complicated, I run the following test case on glibc: > > uint32_t hi, lo, t; > > sscanf("00fafafafa0d0b0b0b0c000000", "%8x%8x%x", &hi, &lo, &t); > > 64-bit: > HI: 00fafafa LO: fa0d0b0b (c000000) > 32-bit: > HI: 00fafafa LO: fa0d0b0b (ffffffff)
But that's exactly the values my pseudo-code gets (well, my "pseudo-code obviously just said
// Now do "sign" and range checking on val
The three sub-parts are: "00fafafa" "fa0d0b0b" and "0b0c000000"
and the third one encounters an overflow in "long" on 32-bit, so it turns into ~0.
And yes, the 64-bit "long" in that third value gets truncated to "uint32" when written to "t" (which is wht that "0b" part just gets lost.
And that's just because of historical C scanf behavior. There's no overflow checking in "int". Only in "long" and "long long".
Linus
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