[llvm] r339027 - Fix raw_fd_ostream::write_impl hang due to an infinite loop with large output

[Owen Reynolds via llvm-commits]

Sorry, may result in a hang, as shown in the bug below:

https://bugs.llvm.org/show_bug.cgi?id=37926

On Wed, Aug 8, 2018 at 12:40 PM, Owen Reynolds <gbreynoo at gmail.com> wrote:

> Hi David,
>
> As this only affects large write attempts and a test failure would result
> in a hang, I was unsure how best to test this. Any suggestions would be
> appreciated.
>
> Thanks,
>
> Owen
>
> On Tue, Aug 7, 2018 at 4:55 AM, David Blaikie <dblaikie at gmail.com> wrote:
>
>> Any chance of a test case?
>>
>> On Mon, Aug 6, 2018 at 9:22 AM Owen Reynolds via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> Author: gbreynoo
>>> Date: Mon Aug  6 09:21:41 2018
>>> New Revision: 339027
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=339027&view=rev
>>> Log:
>>> Fix raw_fd_ostream::write_impl hang due to an infinite loop with large
>>> output
>>>
>>> On windows when raw_fd_ostream::write_impl calls write, a 32 bit input
>>> is required for character count. As a variable with size_t is used for this
>>> argument, on x64 integral demotion occurs. In the case of large files an
>>> infinite loop follows.
>>> See: https://bugs.llvm.org/show_bug.cgi?id=37926
>>> This fix allows the output of files larger than the previous int32 limit.
>>>
>>> Differential Revision: https://reviews.llvm.org/D48948
>>>
>>> Modified:
>>>     llvm/trunk/lib/Support/raw_ostream.cpp
>>>
>>> Modified: llvm/trunk/lib/Support/raw_ostream.cpp
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/
>>> raw_ostream.cpp?rev=339027&r1=339026&r2=339027&view=diff
>>> ============================================================
>>> ==================
>>> --- llvm/trunk/lib/Support/raw_ostream.cpp (original)
>>> +++ llvm/trunk/lib/Support/raw_ostream.cpp Mon Aug  6 09:21:41 2018
>>> @@ -613,10 +613,10 @@ void raw_fd_ostream::write_impl(const ch
>>>    assert(FD >= 0 && "File already closed.");
>>>    pos += Size;
>>>
>>> -  // The maximum write size is limited to SSIZE_MAX because a write
>>> -  // greater than SSIZE_MAX is implementation-defined in POSIX.
>>> -  // Since SSIZE_MAX is not portable, we use SIZE_MAX >> 1 instead.
>>> -  size_t MaxWriteSize = SIZE_MAX >> 1;
>>> +  // The maximum write size is limited to INT32_MAX. A write
>>> +  // greater than SSIZE_MAX is implementation-defined in POSIX,
>>> +  // and Windows _write requires 32 bit input.
>>> +  size_t MaxWriteSize = INT32_MAX;
>>>
>>>  #if defined(__linux__)
>>>    // It is observed that Linux returns EINVAL for a very large write
>>> (>2G).
>>>
>>>
>>> _______________________________________________
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>>> llvm-commits at lists.llvm.org
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>>>
>>
>
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