[Octave-bug-tracker] [bug #33330] fgets hangs octave when reading newline

[Carnë Draug]

URL:
  <http://savannah.gnu.org/bugs/?33330>

                 Summary: fgets hangs octave when reading newline
                 Project: GNU Octave
            Submitted by: carandraug
            Submitted on: Tue 17 May 2011 02:24:03 PM GMT
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.2.4
        Operating System: GNU/Linux

    _______________________________________________________

Details:

Bug report for Octave 3.2.4 configured for i486-pc-linux-gnu

Description:
-----------
If my understanding is correct, octave should return -1 when there's nothing
else to read. When using fgets with at least zenity, it seems to hang. The
problem seems to be on the last character (n) as can be shown by reading one
character at a time.

Repeat-By:
---------
## this will open a dialog box with a progress bar that can be
## moved. Every time the bar is moved the value where it stops
## should be printed
octave-3.2.4 > fid = popen("zenity --scale --print-partial", "r")
## adjust bar to value 16
## adjust bar to value 24
octave-3.2.4 > fgets(fid)
ans = 16

octave-3.2.4 > fgets(fid)
## octave hangs here
## adjust bar to value 46
ans = 24

octave-3.2.4 > fgets(fid)
## octave hangs here
## press OK on the zenity dialog
ans = 46

This example shows the problem being on the last character of the
value by using fgets to read one character at a time

octave-3.2.4 > fid = popen("zenity --scale --print-partial", "r")
## adjust bar to value 16
octave-3.2.4 > fgets(fid,1)
ans = 1
octave-3.2.4 > fgets(fid,1)
ans = 6
octave-3.2.4 > fgets(fid,1)
## octave hangs here instead of returning -1

This shows that zenity works fine in bash
$ zenity --scale --print-partial
## move bar to 16
16

## move bar to 27
27

## move bar to 54
54

## press ok


Configuration (please do not edit this section):
-----------------------------------------------

uname output:     Linux altar 2.6.32-5-686 #1 SMP Tue Mar 8 21:36:00 UTC 2011
i686 GNU/Linux
configure opts:   '--build=i486-linux-gnu' '--prefix=/usr'
'--datadir=/usr/share' '--libdir=/usr/lib' '--libexecdir=/usr/lib'
'--infodir=/usr/share/info' '--mandir=/usr/share/man' '--with-blas=-lblas-3gf'
'--with-lapack=-llapackgf-3' '--with-hdf5' '--with-fftw' '--enable-shared'
'--enable-rpath' '--disable-static' 'build_alias=i486-linux-gnu' 'CC=gcc'
'CFLAGS=-g -O2' 'LDFLAGS=' 'CPPFLAGS=' 'CXX=g++' 'CXXFLAGS=-g -O2'
'F77=gfortran' 'FFLAGS=-g -O2'
Fortran compiler: gfortran
FFLAGS:           -O2 -g
FLIBS:            -lgfortranbegin -lgfortran
CPPFLAGS:         
INCFLAGS:         -I. -I. -I./liboctave -I./src -I./libcruft/misc
C compiler:       gcc, version 4.4.5 (Debian 4.4.5-5) 
CFLAGS:           -O2 -g
CPICFLAG:         -fPIC
C++ compiler:     g++, version 4.4.5
CXXFLAGS:         -O2 -g
CXXPICFLAG:       -fPIC
LD_CXX:           g++
LDFLAGS:          
LIBFLAGS:         -L.
RLD_FLAG:         -Wl,-rpath -Wl,/usr/lib/octave-3.2.4
BLAS_LIBS:        -llapack -lblas
FFTW_LIBS:        -lfftw3 -lfftw3f
LIBS:             -lreadline  -lncurses -ldl -lhdf5 -lz -lm 
LEXLIB:           
LIBGLOB:          
SED:              /bin/sed
DEFS:

  -DPACKAGE_NAME="" -DPACKAGE_TARNAME="" -DPACKAGE_VERSION=""
  -DPACKAGE_STRING="" -DPACKAGE_BUGREPORT="" -DPACKAGE_URL=""
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  -DHAVE_SYS_STAT_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_MEMORY_H=1
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  -D_POSIX_PTHREAD_SEMANTICS=1 -D_TANDEM_SOURCE=1 -DSEPCHAR=':'
  -DSEPCHAR_STR=":" -D__NO_MATH_INLINES=1 -DCXX_NEW_FRIEND_TEMPLATE_DECL=1
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  -DHAVE_LIBM=1 -DHAVE_QHULL=1 -DHAVE_PCRE_COMPILE=1 -DHAVE_PCRE=1
  -DHAVE_REGEXEC=1 -DHAVE_REGEX=1 -DHAVE_ZLIB_H=1 -DHAVE_ZLIB=1
  -DHAVE_HDF5_H=1 -DHAVE_HDF5=1 -DHAVE_H5GGET_NUM_OBJS=1
  -DHAVE_FFTW3=1 -DHAVE_GLPK_H=1 -DHAVE_GLPK=1 -DHAVE_CURL_CURL_H=1
  -DHAVE_CURL=1 -DHAVE_MAGICK=1 -DHAVE_GL_GL_H=1 -DHAVE_GL_GLU_H=1
  -DHAVE_OPENGL=1 -DHAVE_FTGL_FTGL_H=1 -DHAVE_FTGL=1 -DHAVE_FLTK=1
  -DHAVE_IEEE754_DATA_FORMAT=1 -DF77_FUNC(name,NAME)=name ## _
  -DF77_FUNC_(name,NAME)=name ## _ -DHAVE_BLAS=1 -DHAVE_QRUPDATE=1
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  -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_UTSNAME_H=1 -DHAVE_TERMCAP_H=1
  -DHAVE_UNISTD_H=1 -DHAVE_UTIME_H=1 -DHAVE_SSTREAM=1 -DHAVE_TERMIOS_H=1
  -DHAVE_TERMIO_H=1 -DHAVE_SGTTY_H=1 -DHAVE_GLOB_H=1 -DHAVE_FNMATCH_H=1
  -DHAVE_FNMATCH=1 -DHAVE_GLOB=1 -DHAVE_ATEXIT=1 -DHAVE_BASENAME=1
  -DHAVE_BCOPY=1 -DHAVE_BZERO=1 -DHAVE_CANONICALIZE_FILE_NAME=1
  -DHAVE_CHMOD=1 -DHAVE_DUP2=1 -DHAVE_ENDGRENT=1 -DHAVE_ENDPWENT=1
  -DHAVE_EXECVP=1 -DHAVE_EXPM1=1 -DHAVE_EXPM1F=1 -DHAVE_FCNTL=1
  -DHAVE_FORK=1 -DHAVE_FSTAT=1 -DHAVE_GETCWD=1 -DHAVE_GETEGID=1
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  -DHAVE_GETGRNAM=1 -DHAVE_GETPGRP=1 -DHAVE_GETPID=1 -DHAVE_GETPPID=1
  -DHAVE_GETPWENT=1 -DHAVE_GETPWUID=1 -DHAVE_GETTIMEOFDAY=1 -DHAVE_GETUID=1
  -DHAVE_GETWD=1 -DHAVE_KILL=1 -DHAVE_LGAMMA=1 -DHAVE_LGAMMAF=1
  -DHAVE_LGAMMA_R=1 -DHAVE_LGAMMAF_R=1 -DHAVE_LINK=1 -DHAVE_LOCALTIME_R=1
  -DHAVE_LOG1P=1 -DHAVE_LOG1PF=1 -DHAVE_LSTAT=1 -DHAVE_MEMMOVE=1
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  -DHAVE_PIPE=1 -DHAVE_POLL=1 -DHAVE_PUTENV=1 -DHAVE_RAISE=1
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  -DHAVE_SETLOCALE=1 -DHAVE_SETPWENT=1 -DHAVE_SETVBUF=1 -DHAVE_SIGACTION=1
  -DHAVE_SIGLONGJMP=1 -DHAVE_SIGPENDING=1 -DHAVE_SIGPROCMASK=1
  -DHAVE_SIGSUSPEND=1 -DHAVE_SNPRINTF=1 -DHAVE_STAT=1 -DHAVE_STRCASECMP=1
  -DHAVE_STRDUP=1 -DHAVE_STRERROR=1 -DHAVE_STRNCASECMP=1 -DHAVE_STRPTIME=1
  -DHAVE_STRSIGNAL=1 -DHAVE_SYMLINK=1 -DHAVE_TEMPNAM=1 -DHAVE_TGAMMAF=1
  -DHAVE_TRUNC=1 -DHAVE_UMASK=1 -DHAVE_UNAME=1 -DHAVE_UNLINK=1
  -DHAVE_USLEEP=1 -DHAVE_UTIME=1 -DHAVE_VFPRINTF=1 -DHAVE_VSPRINTF=1
  -DHAVE_VSNPRINTF=1 -DHAVE_WAITPID=1 -DHAVE_DECL_EXP2=1 -DHAVE_DECL_ROUND=1
  -DHAVE_DECL_TGAMMA=1 -DHAVE_EXP2=1 -DHAVE_ROUND=1 -DHAVE_TGAMMA=1
  -DHAVE_STRFTIME=1 -DHAVE_C99_VSNPRINTF=1 -DHAVE_LIBDL=1 -DHAVE_DLOPEN=1
  -DHAVE_DLSYM=1 -DHAVE_DLERROR=1 -DHAVE_DLCLOSE=1 -DHAVE_DLOPEN_API=1
  -DENABLE_DYNAMIC_LINKING=1 -DHAVE_TIMEVAL=1 -DHAVE_CMATH_ISNAN=1
  -DHAVE_CMATH_ISNANF=1 -DHAVE_CMATH_ISINF=1 -DHAVE_CMATH_ISINFF=1
  -DHAVE_CMATH_ISFINITE=1 -DHAVE_CMATH_ISFINITEF=1 -DHAVE_FINITE=1
  -DHAVE_ISNAN=1 -DHAVE_ISINF=1 -DHAVE_COPYSIGN=1 -DHAVE_DECL_SIGNBIT=1
  -DHAVE_ACOSH=1 -DHAVE_ACOSHF=1 -DHAVE_ASINH=1 -DHAVE_ASINHF=1
  -DHAVE_ATANH=1 -DHAVE_ATANHF=1 -DHAVE_ERF=1 -DHAVE_ERFF=1 -DHAVE_ERFC=1
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  -DHAVE_TM_ZONE=1 -DUSE_READLINE=1 -DEXCEPTION_IN_MATH=1 -DRETSIGTYPE=void
  -DHAVE_DECL_SYS_SIGLIST=1 -DHAVE_POSIX_SIGNALS=1 -DRETSIGTYPE_IS_VOID=1
  -DHAVE_GETRUSAGE=1 -DHAVE_TIMES=1 -DYYTEXT_POINTER=1

User-preferences (please do not edit this section):
--------------------------------------------------

  EDITOR = emacs
  EXEC_PATH =
/usr/lib/octave/3.2.4/site/exec/i486-pc-linux-gnu:/usr/lib/octave/api-v37/site/exec/i486-pc-linux-gnu:/usr/lib/octave/site/exec/i486-pc-linux-gnu:/usr/lib/octave/3.2.4/exec/i486-pc-linux-gnu:/usr/bin:/usr/local/bin:/usr/bin:/bin:/usr/games
  IMAGE_PATH = .:/usr/share/octave/3.2.4/imagelib
  PAGER = pager
  PS1 = s:#> 
  PS2 = > 
  PS4 = + 
  beep_on_error = 0
  completion_append_char =  
  crash_dumps_octave_core = 1
  echo_executing_commands = 0
  fixed_point_format = 0
  gnuplot_binary = gnuplot
# gnuplot_command_end = <no value or error in displaying it>
# gnuplot_command_plot = <no value or error in displaying it>
# gnuplot_command_replot = <no value or error in displaying it>
# gnuplot_command_splot = <no value or error in displaying it>
# gnuplot_command_title = <no value or error in displaying it>
# gnuplot_command_using = <no value or error in displaying it>
# gnuplot_command_with = <no value or error in displaying it>
  history_file = /home/carandraug/.octave_hist
  history_size = 1024
  ignore_function_time_stamp = system
  info_file = /usr/share/info/octave3.2.info
  info_program = info
  makeinfo_program = makeinfo
  max_recursion_depth = 256
  output_max_field_width = 5
  output_precision = 5
  page_output_immediately = 0
  page_screen_output = 1
# print_answer_id_name = <no value or error in displaying it>
  print_empty_dimensions = 1
  save_precision = 16
  saving_history = 1
  sighup_dumps_octave_core = 1
  sigterm_dumps_octave_core = 1
  silent_functions = 0
  split_long_rows = 1
  string_fill_char =  
  struct_levels_to_print = 2
  suppress_verbose_help_message = 0




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