[LLVMdev] Behaviour of outs()?

[Justin Bogner]

I've fixed (ie, removed) the uses of outs() in lib/IR/GCOV.cpp in
r226961.

"Duncan P. N. Exon Smith" <dexonsmith at apple.com> writes:
> Both of those SGTM.
>
>> On 2015-Jan-23, at 10:32, Reid Kleckner <rnk at google.com> wrote:
>> 
>> We've had this argument before. IMO LLVM should not be in the
>> business of closing stdout, and no code in lib/ should print to
>> stdout because users may expect output there (-o -).
>> 
>> On Fri, Jan 23, 2015 at 10:20 AM, Duncan P. N. Exon Smith
>> <dexonsmith at apple.com> wrote:
>> 
>> > On 2015-Jan-23, at 09:52, mats petersson <mats at planetcatfish.com> wrote:
>> >
>> > I was just fixing a bug that was caused by `stdout` being closed
>> > before the runtime has done `fflush(stdout)` [or however this is
>> > implemented in the runtime].
>> >
>> > The cause of this seems to be that `outs()` returns a static object
>> > created from `raw_fd_stream(STDOUT_FILENO, true)` - the `true` being
>> > the `shouldClose` parameter.
>> >
>> > Surely LLVM is not supposed to close `stdout` as part of its operations?
>> 
>> Looks like this was added in r111643:
>> 
>> commit 5d56d9df928c48571980efe8d4205de8ab557b7c
>> Author: Dan Gohman <gohman at apple.com>
>> Date:   Fri Aug 20 16:44:56 2010 +0000
>> 
>>     Make outs() close its file when its stream is destructed, so that
>>     pending output errors are detected.
>> 
>> 
>>     git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111643
>> 91177308-0d34-0410-b5e6-96231b3b80d8
>> 
>> Certainly looks intentional.  Comment in the code is:
>> 
>>     // Delete the file descriptor when the program exits, forcing error
>>     // detection. If you don't want this behavior, don't use outs().
>> 
>> I don't really have an opinion on whether this is a good idea, but it
>> does suggest that any use of `outs()` in `lib/` is a bug.
>> 
>> $ git grep -l 'outs()' -- lib/
>> lib/ExecutionEngine/Interpreter/ExternalFunctions.cpp
>> lib/IR/GCOV.cpp
>> lib/Support/CommandLine.cpp
>> lib/Support/FormattedStream.cpp
>> lib/Support/TargetRegistry.cpp
>> lib/Support/raw_ostream.cpp
>> lib/Target/CppBackend/CPPBackend.cpp
>> 
>> All of these cases seem to be for outputting help text of some sort.  But
>> probably they should be passed a reference to a `raw_ostream`, so that the
>> caller gets to choose whether or not to use `outs()`.
>> 
>> Were you hitting one of these?
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>
>
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