add these on top of file "jsbsim\src\input_output\string_utilities.cpp"

#define _GNU_SOURCE
#include <_ansi.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <cstdlib>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <iostream>
#include <sstream>
#include <stdio.h>

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 24.96%. Comparing base (f6ae92e) to head (d2a4e7b).

@@           Coverage Diff           @@
##           master    #1200   +/-   ##
=======================================
  Coverage   24.96%   24.96%           
=======================================
  Files         170      170           
  Lines       19283    19283           
=======================================
  Hits         4814     4814           
  Misses      14469    14469           

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@landswellsong, @Saleh-At I'm not sure I'm understanding your request ? Is the PR in its current form complete for the compilation of JSBSim with CygWin or should some further changes be added ?

Please note that some headers are appearing twice in @Saleh-At suggestion (errno.h, stdlib.h, stdio.h, …) and would the PR be modified to include these additional headers then please remove redundant code and update the #ifdef __CYGWIN__ accordingly to avoid polluting the other compilers.

Thanks for the PR.

@bcoconni it works for me as is without additional headers, just the commit which I've sent. I'm unsure why do any additional headers need to be included, it seemed to have only be a problem with one particular unit file.

PR merged. Thanks !