Bug #11553: Disable by default the DTrace support on Linux systems.

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 2.3.0dev (2015-09-26 trunk 51943) [x86_64-linux]
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN

[clopez (Carlos Alberto Lopez Perez)]

The issue is the following:

• Linux has an unnofficial implementation of DTrace (dtrace4linux).
• However, this still don't works as expected and causes either build failures or segfaults at runtime when is enabled on the Ruby build.
  • Examples:
    • https://github.com/dtrace4linux/linux/issues/111
    • https://github.com/dtrace4linux/linux/issues/116

So, I propose to (by default) disable dtrace support on Linux systems.

Otherwise users that try to build Ruby on a Linux system with dtrace4Linux installed (me for example), will end with a broken build.

Linux users willing to try this feature, can still pass the --enable-dtrace flag to enable it.

Patch attached.

[vo.x (Vit Ondruch)]

There is SystemTap which works just fine. And if you don't have installed /usr/bin/dtrace, then it will be disabled anyway. So to say, I am against disabling.

[shevegen (Robert A. Heiler)]

I assume that users will have to use --disable-dtrace to be on the safe side.

It is always a problem with binary yes/no enabling options since there is no middle ground in such a situation.

Ruby in general tries to enable whatever is available on the host system, if it can be found. I am not sure for
which programs this would not be the case but I assume that e. g. just about all the entries in ext/ subdirectory
work like that.

[kosaki (Motohiro KOSAKI)]

If some distro doesn't support SystemTap and does support dtrace4linux officially, I'm ok to disable dtrace feature only on such distros. In the other hands, I have no seen any sense to disable it on Fedora/RHEL/CentOS.

I'm not sure Ubuntu's policy, though.

[nobu (Nobuyoshi Nakada)]

Then disable it if only dtrace4Linux is available?
How can we know SystemTap from dtrace4Linux?

[kosaki (Motohiro KOSAKI)]

Then disable it if only dtrace4Linux is available?

I still doubt no such distribution, though.

[clopez (Carlos Alberto Lopez Perez)]

Ok...

I didn't knew systemtap provided a dtrace binary, neither that it can use the DTrace probes just fine. I just tested it and it worked. Very interesting stuff.

So, I agree that is best keep the default as currently is.

I think dtrace4linux is not shipped with any distro by default. I (Debian user) had to build and install from sources myself.

I think we can close this bug as wontfix/invalid. I would do it myself, but it seems I don't have the required permissions to change the bug status.

[vo.x (Vit Ondruch)]

• Status changed from Open to Rejected