Segmentation faults using setw() manipulator

[Simon Pamment <simon528 at home dot com>]

   I am using a snapshot taken today (23/1/2001) on an i686 linux
   platform and am having a problem with setw() whereby for some
   widths outputting a character string will result in a segmentation
   fault.
   
   The following sample program illustrates this for the case where
   the output string is "ABC" and the format width is 27.

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#include <iostream>
#include <iomanip>

int
main(int, char*[])
{
   std::cout << "Result = [" << std::setw(27) << "ABC" << "]\n";
   
   return 0;
}
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   Trying different combinations of strings and widths suggests that
   there may be somewhat of a pattern. For a given string the above
   program will correctly format it up to a certain width (call it W).
   For widths greater than W the program exhibits one of two modes of
   behaviour depending on whether the length of the string being
   output is even or odd. 

   * If the length is even, the program will seg fault for all lengths
     greater than W. 

   * If the length is odd, the program will output a corrupt string
     (of the correct length) for width W+1 and will seg fault for all
     widths greater than W+1. 

   The following table summarises the situation for successively
   larger strings.
   
       output   |  maximum   | width for  |  minimum
       string   | width for  |  corrupt   | width for
                |  success   |  output    | seg fault
     ===========+============+============+============
      ""        |     24     |            |     25
      "A"       |     24     |     25     |     26
      "AB"      |     25     |            |     26
      "ABC"     |     25     |     26     |     27
      "ABCD"    |     26     |            |     27
      "ABCDE"   |     26     |     27     |     28
      "ABCDEF"  |     27     |            |     28
      "ABCDEFG" |     27     |     28     |     29


   I would be interested to know if anybody else can duplicate this
   problem (at least on an Intel 686 platform).
   
   In case it is useful the following is the output when compiling the
   program with the verbose flag.

      g++ -v -o sw sw.cc

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Reading specs from /work/exp/local/lib/gcc-lib/i686-pc-linux-gnu/2.97/specs
Configured with: /work/exp/local/src/gcc.src/gcc/configure --enable-shared --with-gnu-as --with-gnu-ld --prefix=/work/exp/local
gcc version 2.97 20010123 (experimental)
 /work/exp/local/lib/gcc-lib/i686-pc-linux-gnu/2.97/cc1plus -v -D__GNUC__=2 -D__GNUC_MINOR__=97 -D__GNUC_PATCHLEVEL__=0 -D__ELF__ -Dunix -Dlinux -D__ELF__ -D__unix__ -D__linux__ -D__unix -D__linux -Asystem=posix -D__STDC_HOSTED__=1 -Acpu=i386 -Amachine=i386 -Di386 -D__i386 -D__i386__ -D__tune_i686__ -D__tune_pentiumpro__ sw.cc -D__GNUG__=2 -D_GNU_SOURCE -D__GXX_ABI_VERSION=100 -quiet -dumpbase sw.cc -version -o /tmp/ccyiv5Pa.s
GNU CPP version 2.97 20010123 (experimental) (cpplib) (i386 Linux/ELF)
GNU CPP version 2.97 20010123 (experimental) (cpplib) (i386 Linux/ELF)
GNU C++ version 2.97 20010123 (experimental) (i686-pc-linux-gnu)
	compiled by GNU C version 2.97 20010123 (experimental).
ignoring nonexistent directory "/usr/local/include"
#include "..." search starts here:
#include <...> search starts here:
 /work/exp/local/include/g++-v3
 /work/exp/local/i686-pc-linux-gnu/include/g++-v3
 /work/exp/local/lib/gcc-lib/i686-pc-linux-gnu/2.97/include
 /work/exp/local/i686-pc-linux-gnu/include
 /usr/include
End of search list.
 /work/exp/local/lib/gcc-lib/i686-pc-linux-gnu/2.97/../../../../i686-pc-linux-gnu/bin/as -V -Qy -o /tmp/ccg03AO9.o /tmp/ccyiv5Pa.s
GNU assembler version 2.10.1 (i686-pc-linux-gnu) using BFD version 2.10.1
 /work/exp/local/lib/gcc-lib/i686-pc-linux-gnu/2.97/collect2 -m elf_i386 -dynamic-linker /lib/ld-linux.so.2 -o sw /usr/lib/crt1.o /usr/lib/crti.o /work/exp/local/lib/gcc-lib/i686-pc-linux-gnu/2.97/crtbegin.o -L/work/exp/local/lib/gcc-lib/i686-pc-linux-gnu/2.97 -L/work/exp/local/lib/gcc-lib/i686-pc-linux-gnu/2.97/../../../../i686-pc-linux-gnu/lib -L/work/exp/local/lib/gcc-lib/i686-pc-linux-gnu/2.97/../../.. /tmp/ccg03AO9.o -lstdc++ -lm -lgcc -lc -lgcc /work/exp/local/lib/gcc-lib/i686-pc-linux-gnu/2.97/crtend.o /usr/lib/crtn.o
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