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* Followup on doc issues with USDT
@ 2024-08-21  0:11 Sam James
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From: Sam James @ 2024-08-21  0:11 UTC (permalink / raw)
  To: dtrace

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Hi!

This is a followup to
https://lore.kernel.org/dtrace/87jzgfr2m8.fsf@gentoo.org/.

Carrying on with the USDT tutorial and reference, I noticed a few other
issues.

* In the guide/reference [0], under "Adding Probes to an Application" ->
"Using Statically Defined Probes", a script is provided as 'testscript'.

Unfortunately, the script is broken (it's missing a heredoc for the
Makefile at the very least; there's nothing in the script to stsrt
creating a Makefile, it just launches into some of its (truncated) contents):
```
$ bash /tmp/x
/tmp/x: line 36: test.o:: command not found
test.c:2:10: fatal error: prov.h: No such file or directory
    2 | #include "prov.h"
      |          ^~~~~~~~
compilation terminated.
/tmp/x: line 39: prov.o:: command not found
dtrace: failed to link script prov: failed to open test.o: No such file or directory
/tmp/x: line 42: test:: command not found
/usr/lib/gcc/x86_64-pc-linux-gnu/15/../../../../x86_64-pc-linux-gnu/bin/ld: cannot find prov.o: No such file or directory
/usr/lib/gcc/x86_64-pc-linux-gnu/15/../../../../x86_64-pc-linux-gnu/bin/ld: cannot find test.o: No such file or directory
collect2: error: ld returned 1 exit status
/tmp/x: line 44: EOF: command not found
cc     test.c   -o test
test.c:2:10: fatal error: prov.h: No such file or directory
    2 | #include "prov.h"
      |          ^~~~~~~~
compilation terminated.
make: *** [<builtin>: test] Error 1
dtrace: No such process
```

* In the tutorial [1], under "Using USDT Probes", the 'list the probes'
  instructions don't work.

I get the same "No probe matches description" even when `prime` is
certainly running in another terminal. I've also verified USDT
functionality works using the DTrace testsuite and via manually
constructing examples with an actual probe enabled (not just listing).

```
# dtrace -l -P 'prime*'
  ID   PROVIDER            MODULE                          FUNCTION NAME
dtrace: failed to match prime*:::: No probe matches description
```

When doing `dtrace -l`, it doesn't know to wildcard match USDT (or pid)
probes.

[0] https://docs.oracle.com/en/operating-systems/oracle-linux/dtrace-guide/dtrace-ref-StaticallyDefinedTracingofUserApplications.html#dt_uusdt_sdt
[1] https://docs.oracle.com/en/operating-systems/oracle-linux/dtrace-tutorial/dtrace-tutorial-TracingUserSpaceApplications.html#dtrace_use_usdtprobes

thanks,
sam

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