bug 8858 - Switch to analyze dependencies without printing them

[marler8997]

…or to a file.

This is in response to (https://issues.dlang.org/show_bug.cgi?id=8858). It allows the option -deps- which causes the compiler to analyze dependencies without printing them to stderr or to a file. The typical use case for this would be when a tool like rdmd needs to know all the dependencies but is using the verbose output instead of the dependency specific output.

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[andralex]

This seems like an inflation of options. What's wrong with directing deps to /dev/null? Is outputting deps a bottleneck?

We really need to stop defining new artifacts that are subtly different versions of existing artifacts. The right way to go is improve the existing artifacts.

[marler8997]

Even if output goes to /dev/null (which I don't how you would do that on windows) dmd is still spending cycles generating the output. I estimate this is a very minor performance savings but I thought I would do what I could to try to improve the performance of rdmd in any way I can. Weighing the simplicity of this change with a minor performance savings in rdmd seemed like it could be worth it, but I could go either way on this one. Based on your comments about how this complicates dmd's interface I'll go ahead and close this one.

[andralex]

I estimate this is a very minor performance savings but I thought I would do what I could to try to improve the performance of rdmd in any way I can.

The one way to go about this is to measure.

[marler8997]

For the digger project, on windows (piping output to a file, which is faster than going to the console) it saves about 100 ms out of about 8 seconds. Around a 1 to 2% savings.

[DmitryOlshansky]

This is mostly a problem of Windows console. Piping ti equivalent of /dev/null should nullify this difference. пт, 8 дек. 2017 г. в 5:15, Jonathan Marler <notifications@github.com>:

…

For the digger project, on windows (piping output to a file, which is faster than going to the console) it saves about 100 ms out of about 8 seconds. Around a 1 to 2% savings. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#7400 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AARMqjwoj51la1D2sVMSiyb9kOKMZpqaks5s-Ju0gaJpZM4Q3SDx> .

[rainers]

Even if output goes to /dev/null (which I don't how you would do that on windows)

FYI: the corresponding file on Windows is NUL:.

[marler8997]

Didn't know about NUL:. Piping commands to NUL: seems to work but it doesn't seem to work as a filename passed to -deps. I tried -deps=NUL and -deps=NUL: but I just get Error writing to file 'NUL:'.

[rainers]

I tried -deps=NUL and -deps=NUL: but I just get Error writing to file 'NUL:'.

Both work for me with the released dmd, but not if dmd is built with VC.

[rainers]

I suspect it's not VC related, but caused by #7299