build: fixed cygwin build with malloc wrap

[tridge]

on Cygwin we need to wrap _malloc_r not malloc
See https://cygwin.com/pipermail/cygwin/2000-July/038916.html
fixes #27197

[robustini]

@tridge thanks for the fix!
Cygwin64 correctly compiles the executable for SITL but then Mission Planner executes it and closes the task immediately with an error.
So ok to compile but then it doesn't work in Mission Planner.

[tridge]

Cygwin64 correctly compiles the executable for SITL but then Mission Planner executes it and closes the task immediately with an error.

it starts and runs for me fine.
http://uav.tridgell.net/tmp/cygwin-test/

[robustini]

At the moment I tried with the copter, compiling the master right, it runs it but closes it right away.
i use this simple custom script for a long time and it has always worked:

#!/bin/bash
cd /home/marco/src
rm -rf ardupilot
git clone https://github.com/ardupilot/ardupilot.git
cd ardupilot
git submodule update --init --recursive
modules/waf/waf-light distclean
modules/waf/waf-light configure --board sitl --toolchain x86_64-pc-cygwin
modules/waf/waf-light copter
cp /home/marco/src/ardupilot/build/sitl/bin/arducopter.exe "/cygdrive/c/users/marco/Documents/Mission Planner/sitl"

[tridge]

At the moment I tried with the copter, compiling the master right, it runs it but closes it right away.

I've put working copter here:
http://uav.tridgell.net/tmp/cygwin-test/

[robustini]

At the moment I tried with the copter, compiling the master right, it runs it but closes it right away.

I've put working copter here: http://uav.tridgell.net/tmp/cygwin-test/

Thanks, indeed yours works, mine doesn't but it doesn't give any error in compilation, nice mystery!
But I notice that the size of the exe is different.

[robustini]

I deleted Cygwin completely and reinstalled from scratch with the wiki options, compiled the exe all the time with no problems but it keeps closing.
If I run it manually in the command prompt I get the prompt back without any writing or error.
I can't give an explanation, I don't understand how it works for you after compilation.

[tridge]

@robustini I have tested the version built by CI which is what we distribute, and it works, so I will merge so SITL works again

[robustini]

I'm continuing to investigate because what I've described is happening here, but I'm not coming out of it, and I won't be I think the only one with this problem.