[Bug c++/118693] New: istream& getline (istream& is, string& str, char delim) does not return with long input

[alban_sf--- via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118693

            Bug ID: 118693
           Summary: istream& getline (istream&  is, string& str, char
                    delim) does not return with long input
           Product: gcc
           Version: 14.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alban...@baker-research.com
  Target Milestone: ---

Created attachment 60314
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=60314&action=edit
Test program, .s, .ii files, compiler command and output, sample ouptut.

Hi,

In c++, the function

  istream& getline (istream&  is, string& str, char delim)

doesn't return when"

  1) delim is '>', and

  2) The input to stream "is" consists of 'A' repeated 4926 times followed by
'>'.

In this case, the size of str is usually around 4096 instead of the expected
value of 4926.

However, getline() does return if either:

  1) The input consists of 'A' repeated 2000 times followed by '>'.  In this
case, the size of str is 2000, as expected.

  2) The input consists of 'A' repeated 4926 followed by ">\n>".  In this case,
the size of str is usually around 4096 instead of the expected value of 4926.

I've attached testDecludeFilter.tar.gz that contains:

  1) The test program testGetline.cpp.  Run the test by running testGetline,
and providing the input by cutting the specified number of 'A' characters from
a file, and pasting.

  2) Compiler command.

  3) Compiler output.

  4) .s and .ii files.

  5) Input and output with 4926 'A' characters.

For me a satisfactory solution would be to change the documentation of
getline() to state that the input must not exceed a value before the delim
character.  However, that might not satisfy everyone.

Thanks,
Alban