From @ysth

Created by @ysth

This code should give a "Too late to run CHECK block" warning but
doesn't​:

perl -we'INIT { eval "CHECK {print qq​:in check in init\n​:}" }'

Flags:
    category=core
    severity=low

Site configuration information for perl v5.8.2:

Configured by Gerrit at Fri Nov  7 12:03:56     2003.

Summary of my perl5 (revision 5.0 version 8 subversion 2) configuration:
  Platform:
    osname=cygwin, osvers=1.5.5(0.9432), archname=cygwin-thread-multi-64int
    uname='cygwin_nt-5.0 troubardix 1.5.5(0.9432) 2003-09-20 16:31 i686 unknown unknown cygwin '
    config_args='-de -Dmksymlinks -Duse64bitint -Dusethreads -Doptimize=-O2 -Dman3ext=3pm'
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=define use5005threads=undef useithreads=define usemultiplicity=define
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=define use64bitall=undef uselongdouble=undef
    usemymalloc=y, bincompat5005=undef
  Compiler:
    cc='gcc', ccflags ='-DPERL_USE_SAFE_PUTENV -fno-strict-aliasing',
    optimize='-O2',
    cppflags='-DPERL_USE_SAFE_PUTENV -fno-strict-aliasing'
    ccversion='', gccversion='3.3.1 (cygming special)', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='ld2', ldflags =' -s -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib /lib
    libs=-lgdbm -ldb -lcrypt -lgdbm_compat
    perllibs=-lcrypt -lgdbm_compat
    libc=/usr/lib/libc.a, so=dll, useshrplib=true, libperl=libperl.a
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' -s'
    cccdlflags=' ', lddlflags=' -s -L/usr/local/lib'

Locally applied patches:
    


@INC for perl v5.8.2:
    /usr/lib/perl5/5.8.2/cygwin-thread-multi-64int
    /usr/lib/perl5/5.8.2
    /usr/lib/perl5/site_perl/5.8.2/cygwin-thread-multi-64int
    /usr/lib/perl5/site_perl/5.8.2
    /usr/lib/perl5/site_perl
    .


Environment for perl v5.8.2:
    CYGWIN=tty ntsec title
    HOME=/home/sthoenna
    LANG (unset)
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:/usr/bin:/cygdrive/c/WINDOWS/system32:/cygdrive/c/WINDOWS:/cygdrive/c/WINDOWS/System32/Wbem:/cygdrive/c/Program Files/Common Files/Adaptec Shared/System:/cygdrive/c/Program Files/Rational/common
    PERL_BADLANG (unset)
    SHELL (unset)

From @wolfsage

Thanks for the report.

This is because when nothing is actually happening in the main scope of
the program it's treated as an OP_STUB which causes Perl_newPROG() to
skip out before setting PL_main_start; which is what the warning requires​:

(Inside of Perl_newprog())​:

  if (o->op_type == OP_STUB) {
  PL_comppad_name = 0;
  PL_compcv = 0;
  S_op_destroy(aTHX_ o);

  return; < -- Returns here
  }
  PL_main_root = op_scope(sawparens(scalarvoid(o)));
  PL_curcop = &PL_compiling;
  PL_main_start = LINKLIST(PL_main_root); < -- This is needed

(The warning check​:)

  if (PL_main_start)
  Perl_ck_warner(aTHX_ packWARN(WARN_VOID),
  "Too late to run CHECK block");

This warns correctly for example​:

perl -we'INIT { eval "CHECK {print qq​:in check in init\n​:}" } print "hi";'

Since the CHECK blocks don't actually get run, the warning should still
get generated. Does PL_main_start (and PL_main_root, etc..) need to get
set even when it's just an OP_STUB? Or is this an unlikely / illogical
situation?

-- Matthew Horsfall (alh)

The RT System itself - Status changed from 'new' to 'open'

From @cpansprout

On Sat Dec 17 20​:36​:28 2011, alh wrote​:

Thanks for the report.

This is because when nothing is actually happening in the main scope of
the program it's treated as an OP_STUB which causes Perl_newPROG() to
skip out before setting PL_main_start; which is what the warning requires​:

(Inside of Perl_newprog())​:

     if \(o\->op\_type == OP\_STUB\) \{
        PL\_comppad\_name = 0;
        PL\_compcv = 0;
        S\_op\_destroy\(aTHX\_ o\);

        return; \< \-\- Returns here
    \}
    PL\_main\_root = op\_scope\(sawparens\(scalarvoid\(o\)\)\);
    PL\_curcop = &PL\_compiling;
    PL\_main\_start = LINKLIST\(PL\_main\_root\); \< \-\- This is needed

(The warning check​:)

            if \(PL\_main\_start\)
                Perl\_ck\_warner\(aTHX\_ packWARN\(WARN\_VOID\)\,
                               "Too late to run CHECK block"\);

This warns correctly for example​:

perl -we'INIT { eval "CHECK {print qq​:in check in init\n​:}" } print
"hi";'

Since the CHECK blocks don't actually get run, the warning should still
get generated. Does PL_main_start (and PL_main_root, etc..) need to get
set even when it's just an OP_STUB? Or is this an unlikely / illogical
situation?

It may be very unlikely, but I would not consider it illogical to want
to eval a generated CHECK block.

--

Father Chrysostomos

From @cpansprout

On Sat Dec 17 23​:17​:09 2011, sprout wrote​:

On Sat Dec 17 20​:36​:28 2011, alh wrote​:

Thanks for the report.

This is because when nothing is actually happening in the main scope of
the program it's treated as an OP_STUB which causes Perl_newPROG() to
skip out before setting PL_main_start; which is what the warning
requires​:

(Inside of Perl_newprog())​:

     if \(o\->op\_type == OP\_STUB\) \{
        PL\_comppad\_name = 0;
        PL\_compcv = 0;
        S\_op\_destroy\(aTHX\_ o\);

        return; \< \-\- Returns here
    \}
    PL\_main\_root = op\_scope\(sawparens\(scalarvoid\(o\)\)\);
    PL\_curcop = &PL\_compiling;
    PL\_main\_start = LINKLIST\(PL\_main\_root\); \< \-\- This is needed

(The warning check​:)

            if \(PL\_main\_start\)
                Perl\_ck\_warner\(aTHX\_ packWARN\(WARN\_VOID\)\,
                               "Too late to run CHECK block"\);

This warns correctly for example​:

perl -we'INIT { eval "CHECK {print qq​:in check in init\n​:}" } print
"hi";'

Since the CHECK blocks don't actually get run, the warning should still
get generated. Does PL_main_start (and PL_main_root, etc..) need to get
set even when it's just an OP_STUB? Or is this an unlikely / illogical
situation?

It may be very unlikely, but I would not consider it illogical to want
to eval a generated CHECK block.

On the other hand, this bug report was about the main program, not an
empty eval. So I am apparently rather confused.

--

Father Chrysostomos

From @ysth

On Tue, Jan 10, 2012 at 1​:58 PM, Father Chrysostomos wrote​:

On Sat Dec 17 23​:17​:09 2011, sprout wrote​:

On Sat Dec 17 20​:36​:28 2011, alh wrote​:

This is because when nothing is actually happening in the main scope of
the program it's treated as an OP_STUB which causes Perl_newPROG() to
skip out before setting PL_main_start; which is what the warning
requires​:
....
Since the CHECK blocks don't actually get run, the warning should still
get generated. Does PL_main_start (and PL_main_root, etc..) need to get
set even when it's just an OP_STUB?  Or is this an unlikely / illogical
situation?

It may be very unlikely, but I would not consider it illogical to want
to eval a generated CHECK block.

On the other hand, this bug report was about the main program, not an
empty eval.  So I am apparently rather confused.

This bug is only about a very unlikely to occur case, so is presumably
very low priority. On the other hand, given this bug, there may be
other undesirable consequences of not having PL_main_start set for an
empty main program. On the gripping hand, fixing that will require
significant diligence to see that no bugs are introduced.