scons: mingw-w64-gcc fails due to permission denied (bad environment)

[elieux]

During an attempt to build mingw-w64-nsis, I found out scons has a problem with invoking native programs. Scons, in pursue of reproducible builds, tries to clean up the environment before running its detection (configure-like) tests, but mingw-w64-gcc need some of these environment variables to work reliably.

The problem I observed was that gcc was getting permission denied errors while trying to write to C:\Windows. I checked the environment that this gcc had and it was very small (including MSYSTEM, PATH and few other) and lacked TEMP and TMP, so gcc didn't know where to put its temporary files.

The win32.py platform initializer knows this and passes some vars through to the build environment, see https://bitbucket.org/scons/scons/src/d83ec49e287da9d6cfa22d968ebc24ae3ad8882d/src/engine/SCons/Platform/win32.py?at=default#cl-373. I'd say that our msys.py platform script also needs this, but maybe I'm wrong -- is there a better way of compiling with mingw-w64 from MSYS2 using scons?

[Alexpux]

Look into mingw-w64-mesa package.
I don't have issues with scons building it.
Maybe your issue is poor scons scripts for NSIS

[elieux]

Minimalistic example SConstruct:

EnsureSConsVersion(1,2)
defenv = Environment()
Export('defenv')
conf = defenv.Configure()
if not conf.CheckLibWithHeader('z', 'zlib.h', 'c'):
    print 'zlib is missing!'
    Exit(1)
conf.Finish()

Produces:

$ scons
scons: Reading SConscript files ...
Checking for C library z... no
zlib is missing!

config.log:

file /w/trash/eee/SConstruct,line 7:
    Configure(confdir = .sconf_temp)
scons: Configure: Checking for C library z... 
.sconf_temp/conftest_0.c <-
  |
  |
  |#include "zlib.h"
  |
  |int
  |main() {
  |  
  |return 0;
  |}
  |
gcc -o .sconf_temp/conftest_0.o -c .sconf_temp/conftest_0.c

This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
Cannot create temporary file in C:\Windows\: Permission denied
scons: Configure: no

[elieux]

As for mesa, its SConstruct has lines like ENV = os.environ that explain why it doesn't suffer from this issue.

[elieux]

Here is a patch that works for me: https://gist.github.com/elieux/fd63e62fda6a05778004