[Bug translator/14369] New: Markers with $vars are reported "not found" when missing debuginfo

["jistone at redhat dot com" <sourceware-bugzilla@sourceware.org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=14369

             Bug #: 14369
           Summary: Markers with $vars are reported "not found" when
                    missing debuginfo
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
        AssignedTo: systemtap@sourceware.org
        ReportedBy: jistone@redhat.com
    Classification: Unclassified


This is related to: https://bugzilla.redhat.com/show_bug.cgi?id=841057

As noted there: When we locate an SDT marker, stap takes different paths
depending on the presence of $vars in the handler.  Without any $var, we just
build the probe directly, and life is good.  With a $var, we decide we need
debuginfo, and so that goes down the query_addr path.

Now, if there's anything wrong with the debuginfo, then we end up throwing up
entirely with "semantic error: no match".  An unreachable $var is a problem,
sure, but we should use the right error.  And this also means that @defined()
can't work around this issue.

It doesn't even have to be corrupt debuginfo, as rhbz841057.  Even our sdt_asm
test binary can show this, when you don't have DWARF in part of a file.

First, with no DWARF at all:
> $ gcc ../testsuite/systemtap.base/sdt_asm.S -o sdt_asm.x
> $ ./run-stap -e 'probe process("./sdt_asm.x").mark("*") { println($foo) }' -p2 
> WARNING: cannot find module /home/jistone/systemtap/build/sdt_asm.x debuginfo: No DWARF information found
> semantic error: while resolving probe point: identifier 'process' at <input>:1:7
>         source: probe process("./sdt_asm.x").mark("*") { println($foo) }
>                       ^
> 
> semantic error: no match
> Pass 2: analysis failed.  Try again with another '--vp 01' option.

With some DWARF added (but nothing meaningful near asm probes):
> $ gcc ../testsuite/systemtap.base/sdt_asm.S -o sdt_asm.x -g
> $ ./run-stap -e 'probe process("./sdt_asm.x").mark("*") { println($foo) }' -p2 
> semantic error: while resolving probe point: identifier 'process' at <input>:1:7
>         source: probe process("./sdt_asm.x").mark("*") { println($foo) }
>                       ^
> 
> semantic error: no match
> Pass 2: analysis failed.  Try again with another '--vp 01' option.

And just to sanity check that the probe points do exist:
> $ ./run-stap -e 'probe process("./sdt_asm.x").mark("*") { println(1) }' -p2 
> # probes
> process("/home/jistone/systemtap/build/sdt_asm.x").statement(0x4004ab) /* pc=.absolute+0x4ab */ /* <- process("./sdt_asm.x").mark("memory") = process("./sdt_asm.x").statement(0x4004ab) <- process("./sdt_asm.x").mark("*") */
> process("/home/jistone/systemtap/build/sdt_asm.x").statement(0x4004b1) /* pc=.absolute+0x4b1 */ /* <- process("./sdt_asm.x").mark("a") = process("./sdt_asm.x").statement(0x4004b1) <- process("./sdt_asm.x").mark("*") */
[...]

We ought to fall back on this direct method when the query_addr path fails, and
then the $foo can fail later (if it even survives optimization).

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