cygwin - locale_utils.cc:112:3: error: ‘unsetenv’ was not declared in this scope

[epilsits]

Today's git fails with the following compile error on Windows 10.

locale_utils.cc:112:3: error: ‘unsetenv’ was not declared in this scope
   unsetenv( "LANG" );

First few lines of config.log

This file contains any messages produced by compilers while
running configure, to aid debugging if configure makes a mistake.

It was created by mosh configure 1.3.2, which was
generated by GNU Autoconf 2.69.  Invocation command line was

  $ ./configure

## --------- ##
## Platform. ##
## --------- ##

hostname = exeter
uname -m = x86_64
uname -r = 3.0.1(0.338/5/3)
uname -s = CYGWIN_NT-10.0
uname -v = 2019-02-20 10:19

/usr/bin/uname -p = unknown
/bin/uname -X     = unknown

/bin/arch              = x86_64
/usr/bin/arch -k       = unknown
/usr/convex/getsysinfo = unknown
/usr/bin/hostinfo      = unknown
/bin/machine           = unknown
/usr/bin/oslevel       = unknown
/bin/universe          = unknown

PATH: /usr/local/bin
PATH: /usr/bin
PATH: /cygdrive/c/ProgramData/DockerDesktop/version-bin

The previous version I had was from Jan 2018, and it compiled OK for me.

[andersk]

Ggaaah. Feature test macros. Try make CPPFLAGS=-D_DEFAULT_SOURCE. This was almost certainly broken by a Cygwin change rather than a Mosh change, but nonetheless we should probably add this by default. (Except probably that's going to break some other platform and then we'll need feature tests for our feature test macros. Ggaaah.)

[epilsits]

Lol. That did work, thank you.

To clarify though, I built version mosh 1.3.2 [build mosh-1.3.2-59-g10dca75] again today before updating from git, and it worked. So whatever changed wasn't only Cygwin.

[andersk]

You're right: this was exposed as a side effect of #990, since g++ -std=c++11 defines __STRICT_ANSI__ which disables _DEFAULT_SOURCE by default.