regcomp.c: New build-time warning when compiling with clang

[p5pRT]

Migrated from rt.perl.org#134495 (status was 'open')

Searchable as RT134495$

[p5pRT]

From @jkeenan

When compiling perl 5 blead with clang, I noticed two instances of a
build-time warning not previously noted​:

warning​: result of comparison of constant 223 with expression of type
'char' is always false [-Wtautological-constant-out-of-range-compare].

See attachment.

The code in regcomp.c in question was recently added in commit
3ae8ec4 (2019-09-22).

Karl, can you take a look?

Thank you very much.
Jim Keenan

[p5pRT]

From @jkeenan

[p5p] 531 $ report-build-warnings make.blead.gcc.Wundef.output.txt
File​: make.blead.gcc.Wundef.output.txt

  Wimplicit-fallthrough= 35
  Wundef 155
  Wunused-variable 2

[p5p] 532 $ report-build-warnings make.134494-Wundef.gcc.Wundef.output.txt
File​: make.134494-Wundef.gcc.Wundef.output.txt

  Wimplicit-fallthrough= 35
  Wundef 42
  Wunused-variable 2

[perlmonger​: p5p] $ ~/bin/perl/report-build-warnings make.blead.g++.Wundef.output.txt
File​: make.blead.g++.Wundef.output.txt

  Wformat-overflow= 2
  Wimplicit-fallthrough= 32
  Wpragmas 2
  Wundef 156
  Wunused-variable 2

[perlmonger​: p5p] $ ~/bin/perl/report-build-warnings make.134494-Wundef.g++.Wundef.output.txt
File​: make.134494-Wundef.g++.Wundef.output.txt

  Wformat-overflow= 2
  Wimplicit-fallthrough= 32
  Wpragmas 2
  Wundef 42
  Wunused-variable 2

[p5p] 533 $ report-build-warnings make.blead.clang.Wundef.output.txt
File​: make.blead.clang.Wundef.output.txt

  Wtautological-constant-out-of-range-compare 2
  Wundef 155
  Wunused-variable 2

[p5p] 534 $ report-build-warnings make.134494-Wundef.clang.Wundef.output.txt
File​: make.134494-Wundef.clang.Wundef.output.txt

  Wtautological-constant-out-of-range-compare 2
  Wundef 42
  Wunused-variable 2

[p5pRT]

From @jkeenan

Summary of my perl5 (revision 5 version 31 subversion 5) configuration​:
  Commit id​: d1747a5
  Platform​:
  osname=linux
  osvers=4.15.0-65-generic
  archname=x86_64-linux
  uname='linux zareason 4.15.0-65-generic #74-ubuntu smp tue sep 17 17​:06​:04 utc 2019 x86_64 x86_64 x86_64 gnulinux '
  config_args='-des -Dusedevel -Dcc=clang'
  hint=recommended
  useposix=true
  d_sigaction=define
  useithreads=undef
  usemultiplicity=undef
  use64bitint=define
  use64bitall=define
  uselongdouble=undef
  usemymalloc=n
  default_inc_excludes_dot=define
  bincompat5005=undef
  Compiler​:
  cc='clang'
  ccflags ='-fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
  optimize='-O2'
  cppflags='-fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
  ccversion=''
  gccversion='4.2.1 Compatible Clang 6.0.0 (tags/RELEASE_600/final)'
  gccosandvers=''
  intsize=4
  longsize=8
  ptrsize=8
  doublesize=8
  byteorder=12345678
  doublekind=3
  d_longlong=define
  longlongsize=8
  d_longdbl=define
  longdblsize=16
  longdblkind=3
  ivtype='long'
  ivsize=8
  nvtype='double'
  nvsize=8
  Off_t='off_t'
  lseeksize=8
  alignbytes=8
  prototype=define
  Linker and Libraries​:
  ld='clang'
  ldflags =' -fstack-protector-strong -L/usr/local/lib'
  libpth=/usr/local/lib /usr/lib/llvm-6.0/lib/clang/6.0.0/lib /usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib /lib64 /usr/lib64
  libs=-lpthread -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc
  perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
  libc=libc-2.27.so
  so=so
  useshrplib=false
  libperl=libperl.a
  gnulibc_version='2.27'
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs
  dlext=so
  d_dlsymun=undef
  ccdlflags='-Wl,-E'
  cccdlflags='-fPIC'
  lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector-strong'

Characteristics of this binary (from libperl)​:
  Compile-time options​:
  HAS_TIMES
  PERLIO_LAYERS
  PERL_COPY_ON_WRITE
  PERL_DONT_CREATE_GVSV
  PERL_MALLOC_WRAP
  PERL_OP_PARENT
  PERL_PRESERVE_IVUV
  PERL_USE_DEVEL
  USE_64_BIT_ALL
  USE_64_BIT_INT
  USE_LARGE_FILES
  USE_LOCALE
  USE_LOCALE_COLLATE
  USE_LOCALE_CTYPE
  USE_LOCALE_NUMERIC
  USE_LOCALE_TIME
  USE_PERLIO
  USE_PERL_ATOF
  Built under linux
  Compiled at Oct 12 2019 22​:51​:39
  %ENV​:
  PERL2DIR="/home/jkeenan/gitwork/perl2"
  PERLBREW_HOME="/home/jkeenan/.perlbrew"
  PERLBREW_MANPATH="/home/jkeenan/perl5/perlbrew/perls/perl-5.30.0/man"
  PERLBREW_PATH="/home/jkeenan/perl5/perlbrew/bin​:/home/jkeenan/perl5/perlbrew/perls/perl-5.30.0/bin"
  PERLBREW_PERL="perl-5.30.0"
  PERLBREW_ROOT="/home/jkeenan/perl5/perlbrew"
  PERLBREW_SHELLRC_VERSION="0.84"
  PERLBREW_VERSION="0.84"
  PERL_WORKDIR="/home/jkeenan/gitwork/perl"
  @​INC​:
  lib
  /usr/local/lib/perl5/site_perl/5.31.5/x86_64-linux
  /usr/local/lib/perl5/site_perl/5.31.5
  /usr/local/lib/perl5/5.31.5/x86_64-linux
  /usr/local/lib/perl5/5.31.5

[p5pRT]

From @khwilliamson

On 10/12/19 8​:12 PM, James E Keenan (via RT) wrote​:

# New Ticket Created by James E Keenan
# Please include the string​: [perl #134495]
# in the subject line of all future correspondence about this issue.
# <URL​: https://rt-archive.perl.org/perl5/Ticket/Display.html?id=134495 >

When compiling perl 5 blead with clang, I noticed two instances of a
build-time warning not previously noted​:

warning​: result of comparison of constant 223 with expression of type
'char' is always false [-Wtautological-constant-out-of-range-compare].

See attachment.

The code in regcomp.c in question was recently added in commit
3ae8ec4 (2019-09-22).

Karl, can you take a look?

Thank you very much.
Jim Keenan

This actually doesn't cause a bug due to the the current contents of
Unicode. But there is a bug in the vicinity that I am working on, and
will fix this at the same time.

[p5pRT]

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

[khwilliamson]

This is fixed by 4e4df05