os.putEnv does not compile on cpp backend on Windows

[rockcavera]

os.putEnv does not compile on the cpp backend on Windows. The problem occurs with GCC, CLANG and VCC.

Example

import std/os

putEnv("NimPutEnvTest", "test")

Current Output

GCC

nim cpp test
Hint: used config file 'D:\Nim\config\nim.cfg' [Conf]
Hint: used config file 'D:\Nim\config\config.nims' [Conf]
.......................................................................................
CC: stdlib_digitsutils.nim
CC: stdlib_assertions.nim
CC: stdlib_dollars.nim
CC: stdlib_widestrs.nim
CC: stdlib_io.nim
CC: stdlib_system.nim
CC: stdlib_dynlib.nim
CC: stdlib_winlean.nim
CC: stdlib_times.nim
CC: stdlib_win_setenv.nim
CC: stdlib_os.nim
CC: test.nim
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp: In function 'int setEnvImpl__stdZprivateZwin95setenv_20(NCSTRING, NCSTRING, int)':
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp:199:46: error: no matching function for call to 'mbstowcs_s(size_t*, NI16*&, size_t, char*&, size_t)'
  199 |                         int T30_ = mbstowcs_s((&len), buf2, ((size_t) 32768), name, ((size_t) 32767));
      |                                    ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from d:\mingw64\x86_64-w64-mingw32\include\crtdefs.h:10,
                 from d:\mingw64\x86_64-w64-mingw32\include\limits.h:6,
                 from d:\mingw64\lib\gcc\x86_64-w64-mingw32\11.2.0\include-fixed\limits.h:203,
                 from d:\mingw64\lib\gcc\x86_64-w64-mingw32\11.2.0\include-fixed\syslimits.h:7,
                 from d:\mingw64\lib\gcc\x86_64-w64-mingw32\11.2.0\include-fixed\limits.h:34,
                 from D:\Nim\lib/nimbase.h:269,
                 from C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp:7:
d:\mingw64\x86_64-w64-mingw32\include\sec_api\stdlib_s.h:26:3: note: candidate: 'template<long long unsigned int __size> errno_t mbstowcs_s(size_t*, wchar_t (&)[__size], const char*, size_t)'
   26 |   __DEFINE_CPP_OVERLOAD_SECURE_FUNC_1_2(errno_t, mbstowcs_s, size_t *, _PtNumOfCharConverted, wchar_t, _Dest, const char *, _Source, size_t, _MaxCount)
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
d:\mingw64\x86_64-w64-mingw32\include\sec_api\stdlib_s.h:26:3: note:   template argument deduction/substitution failed:
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp:199:46: note:   mismatched types 'wchar_t [__size]' and 'NI16*' {aka 'short int*'}
  199 |                         int T30_ = mbstowcs_s((&len), buf2, ((size_t) 32768), name, ((size_t) 32767));
      |                                    ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from d:\mingw64\x86_64-w64-mingw32\include\stdlib.h:765,
                 from d:\mingw64\include\c++\11.2.0\cstdlib:75,
                 from d:\mingw64\include\c++\11.2.0\stdlib.h:36,
                 from C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp:9:
d:\mingw64\x86_64-w64-mingw32\include\sec_api\stdlib_s.h:25:27: note: candidate: 'errno_t mbstowcs_s(size_t*, wchar_t*, size_t, const char*, size_t)' (near match)
   25 |   _CRTIMP errno_t __cdecl mbstowcs_s(size_t *_PtNumOfCharConverted,wchar_t *_DstBuf,size_t _SizeInWords,const char *_SrcBuf,size_t _MaxCount);
      |                           ^~~~~~~~~~
d:\mingw64\x86_64-w64-mingw32\include\sec_api\stdlib_s.h:25:27: note:   conversion of argument 2 would be ill-formed:
Error: execution of an external compiler program 'D:\mingw64\bin\g++.exe -c -std=gnu++14 -funsigned-char  -w -fmax-errors=3 -fpermissive -mno-ms-bitfields -DWIN32_LEAN_AND_MEAN   -ID:\Nim\lib -Ic:\Users\Jose\Desktop -o C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp.o C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp' failed with exit code: 1

CLANG

nim cpp --cc:clang test
Hint: used config file 'D:\Nim\config\nim.cfg' [Conf]
Hint: used config file 'D:\Nim\config\config.nims' [Conf]
.......................................................................................
CC: stdlib_digitsutils.nim
CC: stdlib_assertions.nim
CC: stdlib_dollars.nim
CC: stdlib_widestrs.nim
CC: stdlib_io.nim
CC: stdlib_system.nim
CC: stdlib_dynlib.nim
CC: stdlib_winlean.nim
CC: stdlib_times.nim
CC: stdlib_win_setenv.nim
CC: stdlib_os.nim
CC: test.nim
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp:199:15: error: no matching function for call to 'mbstowcs_s'
                        int T30_ = mbstowcs_s((&len), buf2, ((size_t) 32768), name, ((size_t) 32767));
                                   ^~~~~~~~~~
D:\mingw64\x86_64-w64-mingw32\include\sec_api/stdlib_s.h:25:27: note: candidate function not viable: no known conversion from 'NI16 *' (aka 'short *') to 'wchar_t *' for 2nd argument
  _CRTIMP errno_t __cdecl mbstowcs_s(size_t *_PtNumOfCharConverted,wchar_t *_DstBuf,size_t _SizeInWords,const char *_SrcBuf,size_t _MaxCount);
                          ^
D:\mingw64\x86_64-w64-mingw32\include\sec_api/stdlib_s.h:26:50: note: candidate function template not viable: requires 4 arguments, but 5 were provided
  __DEFINE_CPP_OVERLOAD_SECURE_FUNC_1_2(errno_t, mbstowcs_s, size_t *, _PtNumOfCharConverted, wchar_t, _Dest, const char *, _Source, size_t, _MaxCount)
                                                 ^
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp:209:16: error: no matching function for call to '_wgetenv'
                NI16* T33_ = _wgetenv(buf2);
                             ^~~~~~~~
D:\mingw64\x86_64-w64-mingw32\include\stdlib.h:582:28: note: candidate function not viable: no known conversion from 'NI16 *' (aka 'short *') to 'const wchar_t *' for 1st argument
  _CRTIMP wchar_t *__cdecl _wgetenv(const wchar_t *_VarName) __MINGW_ATTRIB_DEPRECATED_SEC_WARN;
                           ^
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp:209:9: error: cannot initialize a variable of type 'NI16 *' (aka 'short *') with an rvalue of type 'wchar_t *'
                NI16* T33_ = _wgetenv(buf2);
                      ^      ~~~~~~~~~~~~~~
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp:212:16: error: no matching function for call to '_wgetenv'
                NI16* T34_ = _wgetenv(buf2);
                             ^~~~~~~~
D:\mingw64\x86_64-w64-mingw32\include\stdlib.h:582:28: note: candidate function not viable: no known conversion from 'NI16 *' (aka 'short *') to 'const wchar_t *' for 1st argument
  _CRTIMP wchar_t *__cdecl _wgetenv(const wchar_t *_VarName) __MINGW_ATTRIB_DEPRECATED_SEC_WARN;
                           ^
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp:212:9: error: cannot initialize a variable of type 'NI16 *' (aka 'short *') with an rvalue of type 'wchar_t *'
                NI16* T34_ = _wgetenv(buf2);
                      ^      ~~~~~~~~~~~~~~
5 errors generated.
Error: execution of an external compiler program 'clang++.exe -c -std=gnu++14 -funsigned-char  -DWIN32_LEAN_AND_MEAN   -ID:\Nim\lib -Ic:\Users\Jose\Desktop -o C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp.o C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp' failed with exit code: 1

VCC

nim cpp --cc:vcc test
Hint: used config file 'D:\Nim\config\nim.cfg' [Conf]
Hint: used config file 'D:\Nim\config\config.nims' [Conf]
.......................................................................................
CC: stdlib_digitsutils.nim
CC: stdlib_assertions.nim
CC: stdlib_dollars.nim
CC: stdlib_widestrs.nim
CC: stdlib_io.nim
CC: stdlib_system.nim
CC: stdlib_dynlib.nim
CC: stdlib_winlean.nim
stdlib_system.nim.cpp
stdlib_digitsutils.nim.cpp
stdlib_dollars.nim.cpp
stdlib_widestrs.nim.cpp
CC: stdlib_times.nim
CC: stdlib_win_setenv.nim
CC: stdlib_os.nim
stdlib_dynlib.nim.cpp
CC: test.nim
stdlib_assertions.nim.cpp
stdlib_io.nim.cpp
stdlib_times.nim.cpp
stdlib_win_setenv.nim.cpp
stdlib_os.nim.cpp
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp(200): error C2664: 'errno_t mbstowcs_s(size_t *,wchar_t *,size_t,const char *,size_t)': não é possível converter um argumento 2 de 'NI16 *' em 'wchar_t *'
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp(200): note: Tipos apontados não são relacionados; conversão requer reinterpret_cast, conversão C-style ou conversão function-style
C:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\ucrt\stdlib.h(911): note: consulte a declaração de 'mbstowcs_s'
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp(210): error C2664: 'wchar_t *_wgetenv(const wchar_t *)': não é possível converter um argumento 1 de 'NI16 *' em 'const wchar_t *'
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp(210): note: Tipos apontados não são relacionados; conversão requer reinterpret_cast, conversão C-style ou conversão function-style
C:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\ucrt\corecrt_wstdlib.h(418): note: consulte a declaração de '_wgetenv'
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp(213): error C2664: 'wchar_t *_wgetenv(const wchar_t *)': não é possível converter um argumento 1 de 'NI16 *' em 'const wchar_t *'
C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp(213): note: Tipos apontados não são relacionados; conversão requer reinterpret_cast, conversão C-style ou conversão function-style
C:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\ucrt\corecrt_wstdlib.h(418): note: consulte a declaração de '_wgetenv'
Error: exestdlib_winlean.nim.cpp
cution of an external compiler program 'vccexe.exe /c --platform:amd64  /nologo /EHsc -DWIN32_LEAN_AND_MEAN   /ID:\Nim\lib /Ic:\Users\Jose\Desktop /nologo /FoC:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp.obj C:\Users\Jose\nimcache\test_d\stdlib_win_setenv.nim.cpp' failed with exit code: 2

Expected Output

Compile without errors.

Possible Solution

The problem is that the backend compilers do not support the conversion from Nim type WideCString to cpp type wchar_t*.

The solution is to rewrite the code to import the c_wgetenv and mbstowcs_s procs with parameters like ptr wchar_t instead of WideCString. Also, pass the parameters with cast[ptr wchar_t]().

Additional Information

nim -v
Nim Compiler Version 1.7.1 [Windows: amd64]
Compiled at 2021-12-27
Copyright (c) 2006-2021 by Andreas Rumpf

git hash: a61bbf7d8d9905a8dd70cc41f4b9e010c3bfee28
active boot switches: -d:release

gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=d:/mingw64/bin/../libexec/gcc/x86_64-w64-mingw32/11.2.0/lto-wrapper.exe
OFFLOAD_TARGET_NAMES=nvptx-none
Target: x86_64-w64-mingw32
Configured with: ../configure --prefix=/R/winlibs64_stage/inst_gcc-11.2.0/share/gcc --build=x86_64-w64-mingw32 --host=x86_64-w64-mingw32 --enable-offload-targets=nvptx-none --with-pkgversion='MinGW-W64 x86_64-posix-seh, built by Brecht Sanders' --with-tune=generic --enable-checking=release --enable-threads=posix --disable-sjlj-exceptions --disable-libunwind-exceptions --disable-serial-configure --disable-bootstrap --enable-host-shared --enable-plugin --disable-default-ssp --disable-rpath --enable-libstdcxx-pch --enable-libstdcxx-time=yes --disable-libstdcxx-debug --disable-version-specific-runtime-libs --with-stabs --disable-symvers --enable-languages=c,c++,fortran,lto,objc,obj-c++,d,jit --disable-gold --disable-nls --disable-stage1-checking --disable-win32-registry --disable-multilib --enable-ld --enable-libquadmath --enable-libada --enable-libssp --enable-libstdcxx --enable-lto --enable-fully-dynamic-string --enable-libgomp --enable-graphite --enable-mingw-wildcard --with-mpc=/d/Prog/winlibs64_stage/custombuilt --with-mpfr=/d/Prog/winlibs64_stage/custombuilt --with-gmp=/d/Prog/winlibs64_stage/custombuilt --with-isl=/d/Prog/winlibs64_stage/custombuilt --enable-install-libiberty --enable-__cxa_atexit --without-included-gettext --with-diagnostics-color=auto --enable-clocale=generic --with-libiconv --with-system-zlib --with-build-sysroot=/R/winlibs64_stage/gcc-11.2.0/build_mingw/mingw-w64 CFLAGS=-I/d/Prog/winlibs64_stage/custombuilt/include/libdl-win32
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.2.0 (MinGW-W64 x86_64-posix-seh, built by Brecht Sanders)

clang -v
(built by Brecht Sanders) clang version 13.0.0
Target: x86_64-w64-windows-gnu
Thread model: posix
InstalledDir: D:\mingw64\bin

Microsoft (R) C/C++ Optimizing Compiler Versão 19.29.30137 para x64
Copyright (C) Microsoft Corporation. Todos os direitos reservados.

[ringabout]

There is a regression since #20084