p5pRT
commented
12 years ago From @icerider70
Created by philip.monsen@pobox.com
Under +O1 compiler optimization\, the test passes fine:
$ ./perl -I./lib ext/XS-APItest/t/coplabel.t 1..1 ok 1
But when +O2 is used\, not so much:
$ ./perl -I./lib ext/XS-APItest/t/coplabel.t 1..1 fail # cop_fetch_label label at ext/XS-APItest/t/coplabel.t line 7.
I've filed this as a bug because the default -Doptimize value when Configure is run is '+O2 +Onolimit'.
I believe the issue is partly due to reordering of instructions. Here's the C code generated from APItest.xs:
XS_EUPXS(XS_XS__APItest_test_coplabel) { dVAR; dXSARGS; if (items != 0) croak_xs_usage(cv\, ""); { #line 2643 "APItest.xs" COP *cop; const char *label; STRLEN len; U32 utf8; #line 4476 "APItest.c" #line 2648 "APItest.xs" cop = &PL_compiling; Perl_cop_store_label(aTHX_ cop\, "foo"\, 3\, 0); label = Perl_cop_fetch_label(aTHX_ cop\, &len\, &utf8); if (strcmp(label\,"foo")) croak("fail # cop_fetch_label label"); if (len != 3) croak("fail # cop_fetch_label len"); if (utf8) croak("fail # cop_fetch_label utf8"); /* SMALL GERMAN UMLAUT A */ Perl_cop_store_label(aTHX_ cop\, "foC$"\, 4\, SVf_UTF8); label = Perl_cop_fetch_label(aTHX_ cop\, &len\, &utf8); if (strcmp(label\,"foC$")) croak("fail # cop_fetch_label label"); if (len != 4) croak("fail # cop_fetch_label len"); if (!utf8) croak("fail # cop_fetch_label utf8"); #line 4490 "APItest.c" } XSRETURN_EMPTY; }
Here's a snippet from a gdb debugging session under +O1:
2649 Perl_cop_store_label(aTHX_ cop\, "foo"\, 3\, 0); (gdb) n 2650 label = Perl_cop_fetch_label(aTHX_ cop\, &len\, &utf8); (gdb) n 2651 if (strcmp(label\,"foo")) croak("fail # cop_fetch_label label"); (gdb) n 2652 if (len != 3) croak("fail # cop_fetch_label len"); (gdb) n 2653 if (utf8) croak("fail # cop_fetch_label utf8"); (gdb) n 2655 Perl_cop_store_label(aTHX_ cop\, "foä"\, 4\, SVf_UTF8); (gdb) n 2656 label = Perl_cop_fetch_label(aTHX_ cop\, &len\, &utf8); (gdb) n 2657 if (strcmp(label\,"foä")) croak("fail # cop_fetch_label label"); (gdb) p label $1 = 0x600000000051ac3d "fo\303\244" (gdb) p len $2 = 4 (gdb) p utf8 $3 = 536870912 (gdb) n 2658 if (len != 4) croak("fail # cop_fetch_label len"); (gdb) n 2659 if (!utf8) croak("fail # cop_fetch_label utf8"); (gdb) n 4491 XSRETURN_EMPTY;
Note the contrast when +O2 is in force:
2650 label = Perl_cop_fetch_label(aTHX_ cop\, &len\, &utf8);
(gdb) n
2651 if (strcmp(label\,"foo")) croak("fail # cop_fetch_label
label");
(gdb) p label
$1 = \
Due to the opaqueness imposed by the +O2 optimizations\, it's hard to tell exactly what happened\, but somehow the optimizations are inducing a false exit path.
Reordering the tests within this function\, and changing strcmp() to memcmp()\, appears to resolve the issue (i.e. we can compile with the default of -Doptimize='+O2 +Onolimit' and this test passes).
Patch forthcoming.
Migrated from rt.perl.org#103668 (status was 'resolved')
Searchable as RT103668$