[Bug translator/14509] New: Reshuffled chain error messages are misleading for DWARF-search-failures

["smakarov at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=14509

             Bug #: 14509
           Summary: Reshuffled chain error messages are misleading for
                    DWARF-search-failures
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
        AssignedTo: systemtap@sourceware.org
        ReportedBy: smakarov@redhat.com
    Classification: Unclassified


When trying to resolve a probe such as process("/bin/ls").function("foo"),
where the function doesn't exist, SystemTap used to print the following:

semantic error: no match while resolving probe point: identifier 'process' at
<input>:1:7
source: probe process("/opt/codebase/build/a.out").function("foo")

Now error chaining (in derive_probes() in elaborate.cxx) has been reshuffled to
look like this:

semantic error: while resolving probe point: identifier 'process' at
<input>:1:7
source: probe process("/opt/codebase/build/a.out").function("foo")
^

semantic error: no match

This looks like a message saying that the entire process(...) category of
probes doesn't exist, rather than that one function in the executable doesn't
exist. The user may likely be misled into thinking that their system has
somehow misconfigured uprobes.

There are various more or less painful ways of making this error more
understandable, and one of them should be employed, possibly in conjunction
with solving PR14184. Ideally the result should be to change the token so the
error points to "foo", and expand the "no match" message to something specific
to the DWARF probe builder.

Just as importantly, there might be other contexts where the new chaining is
misleading, so that might also be worth investigating.

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