[llvm-dev] error building LLVM opt tool under Cygwin

[s nedunuri via llvm-dev]

On Fri, Mar 1, 2019 at 4:43 PM Rui Ueyama <ruiu at google.com> wrote:

> On Thu, Feb 28, 2019 at 3:15 PM Eli Friedman via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> > -----Original Message-----
>> > From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of s n via
>> llvm-dev
>> > Sent: Wednesday, February 27, 2019 9:31 PM
>> > To: llvm-dev at lists.llvm.org
>> > Subject: [EXT] [llvm-dev] error building LLVM opt tool under Cygwin
>> >
>> > Hello, I downloaded and built llvm-7.0.1 as per the instructions on the
>> > website docs. It seems that I can run many of the tools in build/bin (eg
>> > llvm-diff or count etc) with the exception of opt where I get "-bash:
>> > ./opt.exe: cannot execute binary file: Exec format error". I tried
>> > rebuilding just opt but still no luck. An ideas?
>>
>> "Exec format error" means the file is corrupted, or not an executable.
>> Not sure how you would get that result without the build producing some
>> sort of error message.  You could try "file opt.exe" to rule out the
>> possibility that it's something that isn't an executable.  Maybe try
>> cleaning and rebuilding.  Also, use a verbose build ("make VERBOSE=1" or
>> "ninja -v") to see the command that actually produces opt.exe.
>>
>
> When the disk is almost full, some tools create broken executable. I don't
> know if this is the case though. (If that's the case, you need to delete
> files to fix it.)
>
hi, no I'm pretty sure its not a problem with disk space - i have 139Gb
free.

>
> In general, Cygwin is not well tested; if you can, I'd recommend using
>> mingw or Visual Studio instead.
>>
> Its very odd because a random selection of other generated executables
seem to run just fine.  What about opt could cause problems with cygwin? I
am running the executable from llvm-project/build/bin - I assume that's
fine?

>
>> >
>> > This is frustrating because opt is the tool I am most interested in, and
>> > the reason I built llvm at all instead of relying on the binary
>> > distribution.
>> >
>> > On a somewhat unrelated note, what does make install actually do. I ran
>> > "cmake -DMAKE_INSTALL_PREFIX=..../llvm-project/install -P
>> > cmake_Install.cmake" and it ran for a long time, but I couldn't tell
>> > what it actually did. eg I couldn't see any directory called
>> > ..../llvm=project/install"
>>
>> The correct option is "-DCMAKE_INSTALL_PREFIX=..."; like you would
>> expect, it's supposed to set the install prefix.
>>
> sorry that was a typo in transcribing. The actual text I typed was
"-DCMAKE_INSTALL_PREFIX=...". But I am still not clear what it actually does

thanks

>
>> -Eli
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>
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