Hi!

I've investigated some more.

On 2020-11-03T13:31:53+0100, I wrote:
> Help.  Save the attached file as 'gcc/testsuite/c-c++-common/goacc/l_.c',
> and then run:
>
>     $ make check-gcc-c++ RUNTESTFLAGS=--all\ goacc.exp=l_.c
>
> As expected for '-std=c++98' testing, which comes first:
>
>     PASS: c-c++-common/goacc/l_.c  -std=c++98  (test for errors, line 14)
>     PASS: c-c++-common/goacc/l_.c  -std=c++98  (test for warnings, line 11)
>     PASS: c-c++-common/goacc/l_.c  -std=c++98 (test for excess errors)
>     WARNING: dg-line var l1 defined, but not used
>     WARNING: dg-line var l2 defined, but not used
>     WARNING: dg-line var l3 defined, but not used
>
> But then it goes on with '-std=c++14', etc. testing:
>
>     UNRESOLVED: c-c++-common/goacc/l_.c  -std=c++14  (test for errors, line 
> 14)
>     PASS: c-c++-common/goacc/l_.c  -std=c++14  (test for warnings, line 11)
>     PASS: c-c++-common/goacc/l_.c  -std=c++14 (test for excess errors)
>     WARNING: dg-line var l1 defined, but not used
>     WARNING: dg-line var l2 defined, but not used
>     WARNING: dg-line var l3 defined, but not used
>     UNRESOLVED: c-c++-common/goacc/l_.c  -std=c++17  (test for errors, line 
> 14)
>     PASS: c-c++-common/goacc/l_.c  -std=c++17  (test for warnings, line 11)
>     PASS: c-c++-common/goacc/l_.c  -std=c++17 (test for excess errors)
>     WARNING: dg-line var l1 defined, but not used
>     WARNING: dg-line var l2 defined, but not used
>     WARNING: dg-line var l3 defined, but not used
>     UNRESOLVED: c-c++-common/goacc/l_.c  -std=c++2a  (test for errors, line 
> 14)
>     PASS: c-c++-common/goacc/l_.c  -std=c++2a  (test for warnings, line 11)
>     PASS: c-c++-common/goacc/l_.c  -std=c++2a (test for excess errors)
>     WARNING: dg-line var l1 defined, but not used
>     WARNING: dg-line var l2 defined, but not used
>     WARNING: dg-line var l3 defined, but not used
>
>                     === g++ Summary ===
>
>     # of expected passes            9
>     # of unresolved testcases       3
>
> Why is suddenly the "test for errors, line 14" an UNRESOLVED?  (The
> compiler diagnostics are as expected.  This testcase doesn't depend on
> '-std=[...]' at all.)
>
> And now the "funny" thing: if I disable any of the 'dg-line' directives,
> it works as expected, all-PASS.  But note that "test for errors, line 14"
> doesn't even use a 'dg-line'-captured line number.  (It uses absoute line
> numbers.  Same issue visible when using relative ones, or when actually
> using 'dg-line' for these.)
>
>
> I reduced this from a much bigger testcase, and had originally found this
> not with 'check-gcc-c++' but with 'check-gcc-c': things worked fine as
> long as testing just a single testcase, but broke when testing several.
> (Again the symptom was that the first testcase worked fine, but the
> following ones had an unexpecte UNRESOLVED for the first 'dg-error' (only
> for the first!).)  Supposedly, 'check-gcc-c++' with a single testcase but
> testing several variants is exhibiting the same problem.

The problem is indeed related to the "WARNING: dg-line var [...] defined,
but not used" diagnostics.  These are produced via DejaGnu 'warning'
calls, which increments 'warncnt', and once that reaches
'warning_threshold' (default per '/usr/share/dejagnu/framework.exp' is:
'set warning_threshold 3'), this triggers UNRESOLVED via
'/usr/share/dejagnu/framework.exp:record_test'.  That this UNRESOLVED
appears for the *next* testcase, must be considered some kind of bug
(improper use of 'warning'?), I suppose.

The following works around that:

    --- gcc/testsuite/lib/gcc-dg.exp
    +++ gcc/testsuite/lib/gcc-dg.exp
    @@ -1008,6 +1008,8 @@ if { [info procs saved-dg-test] == [list] } {
                } else {
                    regsub {^saved_linenr_} $varname "" org_varname
                    warning "dg-line var $org_varname defined, but not used"
    +               global warncnt
    +               incr warncnt -1
                }
            }
            unset save_linenr_varnames

..., or:

    --- gcc/testsuite/lib/gcc-dg.exp
    +++ gcc/testsuite/lib/gcc-dg.exp
    @@ -1007,7 +1007,7 @@ if { [info procs saved-dg-test] == [list] } {
                    eval unset $varname_used
                } else {
                    regsub {^saved_linenr_} $varname "" org_varname
    -               warning "dg-line var $org_varname defined, but not used"
    +               verbose "WARNING: dg-line var $org_varname defined, but not 
used" 0
                }
            }
            unset save_linenr_varnames

..., or hopefully something less hacky.


The question is, what quality/severity should the "dg-line var [...]
defined, but not used" diagnostic have?

For example, "FAIL":

    --- gcc/testsuite/lib/gcc-dg.exp
    +++ gcc/testsuite/lib/gcc-dg.exp
    @@ -1007,7 +1007,7 @@ if { [info procs saved-dg-test] == [list] } {
                    eval unset $varname_used
                } else {
                    regsub {^saved_linenr_} $varname "" org_varname
    -               warning "dg-line var $org_varname defined, but not used"
    +               fail "dg-line var $org_varname defined, but not used"
                }
            }
            unset save_linenr_varnames

    PASS: c-c++-common/goacc/l_.c  -std=c++98  (test for errors, line 14)
    PASS: c-c++-common/goacc/l_.c  -std=c++98  (test for warnings, line 11)
    PASS: c-c++-common/goacc/l_.c  -std=c++98 (test for excess errors)
    FAIL: dg-line var l1 defined, but not used
    FAIL: dg-line var l2 defined, but not used
    FAIL: dg-line var l3 defined, but not used
    PASS: c-c++-common/goacc/l_.c  -std=c++14  (test for errors, line 14)
    [...]

..., or "NOTE":

    --- gcc/testsuite/lib/gcc-dg.exp
    +++ gcc/testsuite/lib/gcc-dg.exp
    @@ -1007,7 +1007,7 @@ if { [info procs saved-dg-test] == [list] } {
                    eval unset $varname_used
                } else {
                    regsub {^saved_linenr_} $varname "" org_varname
    -               warning "dg-line var $org_varname defined, but not used"
    +               note "dg-line var $org_varname defined, but not used"
                }
            }
            unset save_linenr_varnames

    Running [...]/gcc/testsuite/g++.dg/goacc/goacc.exp ...
    PASS: c-c++-common/goacc/l_.c  -std=c++98  (test for errors, line 14)
    PASS: c-c++-common/goacc/l_.c  -std=c++98  (test for warnings, line 11)
    PASS: c-c++-common/goacc/l_.c  -std=c++98 (test for excess errors)
    NOTE: dg-line var l1 defined, but not used
    NOTE: dg-line var l2 defined, but not used
    NOTE: dg-line var l3 defined, but not used
    PASS: c-c++-common/goacc/l_.c  -std=c++14  (test for errors, line 14)
    [...]

..., or something else?


Grüße
 Thomas
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