Avoid sharing the parent process's stdin handle to python on Windows …

…+ other Windows bat script fixes (emscripten-core#15146)

* Avoid sharing the parent process's stdin handle to python when invoking python via emcc.bat script, to prevent a rare python deadlock hang.

* Fix Windows .bat scripts from leaking set env. vars.
Work around a Windows 7 batch script exit code issue.
Work around a Windows Python spawn issue: https://bugs.python.org/issue34780

* Do not let anything come between python subprocess spawn and the exit statement (an if() statement would taint the 0 variable)

* Fix bad automerge

* Avoid dispatching emcc from within an if() block in .bat file

* Always use exit in .bat scripts to avoid goto tainting ERRORLEVEL

ChangeLog.md

@@ -36,6 +36,10 @@ See docs/process.md for more on how version tagging works.
   `__syscall22`) to name-based (e.g. `__syscall_open`).  This should not be
   a visible change except for folks trying to intercept/implement syscalls
   in native code (#15202).
+- Fixed launcher batch script issues on Windows, and added two env. vars
+  EM_WORKAROUND_PYTHON_BUG_34780 and EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG that
+  can be enabled to work around a Windows Python issue
+  https://bugs.python.org/issue34780 , and a Windows 7 exit code issue (#15146)
 
 2.0.31 - 10/01/2021
 -------------------

em++.bat

@@ -5,18 +5,65 @@
 :: To make modifications to this file, edit `tools/run_python_compiler.bat` and
 :: then run `tools/create_entry_points.py`
 
+:: All env. vars specified in this file are to be local only to this script.
+@setlocal
+
 @set EM_PY=%EMSDK_PYTHON%
 @if "%EM_PY%"=="" (
   set EM_PY=python
 )
 
+:: If _EMCC_CCACHE is not set, do a regular invocation of the python compiler driver.
+:: Otherwise remove the ccache env. var, and then reinvoke this script with ccache enabled.
 @if "%_EMCC_CCACHE%"=="" (
-  :: Do regular invocation of the python compiler driver
   set CMD="%EM_PY%" "%~dp0\%~n0.py"
 ) else (
-  :: Remove the ccache env. var, invoke ccache and re-enter this script to take the above branch.
   set _EMCC_CCACHE=
   set CMD=ccache "%~dp0\%~n0.bat"
 )
 
+:: Python Windows bug https://bugs.python.org/issue34780: If this script was invoked via a
+:: shared stdin handle from the parent process, and that parent process stdin handle is in
+:: a certain state, running python.exe might hang here. To work around this, if
+:: EM_WORKAROUND_PYTHON_BUG_34780 is defined, invoke python with '< NUL' stdin to avoid
+:: sharing the parent's stdin handle to it, avoiding the hang.
+
+:: On Windows 7, the compiler batch scripts are observed to exit with a non-zero errorlevel,
+:: even when the python executable above did succeed and quit with errorlevel 0 above.
+:: On Windows 8 and newer, this issue has not been observed. It is possible that this
+:: issue is related to the above python bug, but this has not been conclusively confirmed,
+:: so using a separate env. var EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG to enable the known
+:: workaround this issue, which is to explicitly quit the calling process with the previous
+:: errorlevel from the above command.
+
+:: Also must use goto to jump to the command dispatch, since we cannot invoke emcc from
+:: inside a if() block, because if a cmdline param would contain a char '(' or ')', that
+:: would throw off the parsing of the cmdline arg.
+@if "%EM_WORKAROUND_PYTHON_BUG_34780%"=="" (
+  @if "%EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG%"=="" (
+    goto NORMAL
+  ) else (
+    goto NORMAL_EXIT
+  )
+) else (
+  @if "%EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG%"=="" (
+    goto MUTE_STDIN
+  ) else (
+    goto MUTE_STDIN_EXIT
+  )
+)
+
+:NORMAL_EXIT
+@%CMD% %*
+@exit %ERRORLEVEL%
+
+:MUTE_STDIN
+@%CMD% %* < NUL
+@exit /b %ERRORLEVEL%
+
+:MUTE_STDIN_EXIT
+@%CMD% %* < NUL
+@exit %ERRORLEVEL%
+
+:NORMAL
 @%CMD% %*

em-config.bat

@@ -5,10 +5,56 @@
 :: To make modifications to this file, edit `tools/run_python.bat` and then run
 :: `tools/create_entry_points.py`
 
+:: All env. vars specified in this file are to be local only to this script.
 @setlocal
+
 @set EM_PY=%EMSDK_PYTHON%
 @if "%EM_PY%"=="" (
   set EM_PY=python
 )
 
+:: Python Windows bug https://bugs.python.org/issue34780: If this script was invoked via a
+:: shared stdin handle from the parent process, and that parent process stdin handle is in
+:: a certain state, running python.exe might hang here. To work around this, if
+:: EM_WORKAROUND_PYTHON_BUG_34780 is defined, invoke python with '< NUL' stdin to avoid
+:: sharing the parent's stdin handle to it, avoiding the hang.
+
+:: On Windows 7, the compiler batch scripts are observed to exit with a non-zero errorlevel,
+:: even when the python executable above did succeed and quit with errorlevel 0 above.
+:: On Windows 8 and newer, this issue has not been observed. It is possible that this
+:: issue is related to the above python bug, but this has not been conclusively confirmed,
+:: so using a separate env. var EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG to enable the known
+:: workaround this issue, which is to explicitly quit the calling process with the previous
+:: errorlevel from the above command.
+
+:: Also must use goto to jump to the command dispatch, since we cannot invoke emcc from
+:: inside a if() block, because if a cmdline param would contain a char '(' or ')', that
+:: would throw off the parsing of the cmdline arg.
+@if "%EM_WORKAROUND_PYTHON_BUG_34780%"=="" (
+  @if "%EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG%"=="" (
+    goto NORMAL
+  ) else (
+    goto NORMAL_EXIT
+  )
+) else (
+  @if "%EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG%"=="" (
+    goto MUTE_STDIN
+  ) else (
+    goto MUTE_STDIN_EXIT
+  )
+)
+
+:NORMAL_EXIT
+@"%EM_PY%" "%~dp0\%~n0.py" %*
+@exit %ERRORLEVEL%
+
+:MUTE_STDIN
+@"%EM_PY%" "%~dp0\%~n0.py" %* < NUL
+@exit /b %ERRORLEVEL%
+
+:MUTE_STDIN_EXIT
+@"%EM_PY%" "%~dp0\%~n0.py" %* < NUL
+@exit %ERRORLEVEL%
+
+:NORMAL
 @"%EM_PY%" "%~dp0\%~n0.py" %*

emar.bat

@@ -5,10 +5,56 @@
 :: To make modifications to this file, edit `tools/run_python.bat` and then run
 :: `tools/create_entry_points.py`
 
+:: All env. vars specified in this file are to be local only to this script.
 @setlocal
+
 @set EM_PY=%EMSDK_PYTHON%
 @if "%EM_PY%"=="" (
   set EM_PY=python
 )
 
+:: Python Windows bug https://bugs.python.org/issue34780: If this script was invoked via a
+:: shared stdin handle from the parent process, and that parent process stdin handle is in
+:: a certain state, running python.exe might hang here. To work around this, if
+:: EM_WORKAROUND_PYTHON_BUG_34780 is defined, invoke python with '< NUL' stdin to avoid
+:: sharing the parent's stdin handle to it, avoiding the hang.
+
+:: On Windows 7, the compiler batch scripts are observed to exit with a non-zero errorlevel,
+:: even when the python executable above did succeed and quit with errorlevel 0 above.
+:: On Windows 8 and newer, this issue has not been observed. It is possible that this
+:: issue is related to the above python bug, but this has not been conclusively confirmed,
+:: so using a separate env. var EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG to enable the known
+:: workaround this issue, which is to explicitly quit the calling process with the previous
+:: errorlevel from the above command.
+
+:: Also must use goto to jump to the command dispatch, since we cannot invoke emcc from
+:: inside a if() block, because if a cmdline param would contain a char '(' or ')', that
+:: would throw off the parsing of the cmdline arg.
+@if "%EM_WORKAROUND_PYTHON_BUG_34780%"=="" (
+  @if "%EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG%"=="" (
+    goto NORMAL
+  ) else (
+    goto NORMAL_EXIT
+  )
+) else (
+  @if "%EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG%"=="" (
+    goto MUTE_STDIN
+  ) else (
+    goto MUTE_STDIN_EXIT
+  )
+)
+
+:NORMAL_EXIT
+@"%EM_PY%" "%~dp0\%~n0.py" %*
+@exit %ERRORLEVEL%
+
+:MUTE_STDIN
+@"%EM_PY%" "%~dp0\%~n0.py" %* < NUL
+@exit /b %ERRORLEVEL%
+
+:MUTE_STDIN_EXIT
+@"%EM_PY%" "%~dp0\%~n0.py" %* < NUL
+@exit %ERRORLEVEL%
+
+:NORMAL
 @"%EM_PY%" "%~dp0\%~n0.py" %*

embuilder.bat

@@ -5,10 +5,56 @@
 :: To make modifications to this file, edit `tools/run_python.bat` and then run
 :: `tools/create_entry_points.py`
 
+:: All env. vars specified in this file are to be local only to this script.
 @setlocal
+
 @set EM_PY=%EMSDK_PYTHON%
 @if "%EM_PY%"=="" (
   set EM_PY=python
 )
 
+:: Python Windows bug https://bugs.python.org/issue34780: If this script was invoked via a
+:: shared stdin handle from the parent process, and that parent process stdin handle is in
+:: a certain state, running python.exe might hang here. To work around this, if
+:: EM_WORKAROUND_PYTHON_BUG_34780 is defined, invoke python with '< NUL' stdin to avoid
+:: sharing the parent's stdin handle to it, avoiding the hang.
+
+:: On Windows 7, the compiler batch scripts are observed to exit with a non-zero errorlevel,
+:: even when the python executable above did succeed and quit with errorlevel 0 above.
+:: On Windows 8 and newer, this issue has not been observed. It is possible that this
+:: issue is related to the above python bug, but this has not been conclusively confirmed,
+:: so using a separate env. var EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG to enable the known
+:: workaround this issue, which is to explicitly quit the calling process with the previous
+:: errorlevel from the above command.
+
+:: Also must use goto to jump to the command dispatch, since we cannot invoke emcc from
+:: inside a if() block, because if a cmdline param would contain a char '(' or ')', that
+:: would throw off the parsing of the cmdline arg.
+@if "%EM_WORKAROUND_PYTHON_BUG_34780%"=="" (
+  @if "%EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG%"=="" (
+    goto NORMAL
+  ) else (
+    goto NORMAL_EXIT
+  )
+) else (
+  @if "%EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG%"=="" (
+    goto MUTE_STDIN
+  ) else (
+    goto MUTE_STDIN_EXIT
+  )
+)
+
+:NORMAL_EXIT
+@"%EM_PY%" "%~dp0\%~n0.py" %*
+@exit %ERRORLEVEL%
+
+:MUTE_STDIN
+@"%EM_PY%" "%~dp0\%~n0.py" %* < NUL
+@exit /b %ERRORLEVEL%
+
+:MUTE_STDIN_EXIT
+@"%EM_PY%" "%~dp0\%~n0.py" %* < NUL
+@exit %ERRORLEVEL%
+
+:NORMAL
 @"%EM_PY%" "%~dp0\%~n0.py" %*

emcc.bat

@@ -5,18 +5,65 @@
 :: To make modifications to this file, edit `tools/run_python_compiler.bat` and
 :: then run `tools/create_entry_points.py`
 
+:: All env. vars specified in this file are to be local only to this script.
+@setlocal
+
 @set EM_PY=%EMSDK_PYTHON%
 @if "%EM_PY%"=="" (
   set EM_PY=python
 )
 
+:: If _EMCC_CCACHE is not set, do a regular invocation of the python compiler driver.
+:: Otherwise remove the ccache env. var, and then reinvoke this script with ccache enabled.
 @if "%_EMCC_CCACHE%"=="" (
-  :: Do regular invocation of the python compiler driver
   set CMD="%EM_PY%" "%~dp0\%~n0.py"
 ) else (
-  :: Remove the ccache env. var, invoke ccache and re-enter this script to take the above branch.
   set _EMCC_CCACHE=
   set CMD=ccache "%~dp0\%~n0.bat"
 )
 
+:: Python Windows bug https://bugs.python.org/issue34780: If this script was invoked via a
+:: shared stdin handle from the parent process, and that parent process stdin handle is in
+:: a certain state, running python.exe might hang here. To work around this, if
+:: EM_WORKAROUND_PYTHON_BUG_34780 is defined, invoke python with '< NUL' stdin to avoid
+:: sharing the parent's stdin handle to it, avoiding the hang.
+
+:: On Windows 7, the compiler batch scripts are observed to exit with a non-zero errorlevel,
+:: even when the python executable above did succeed and quit with errorlevel 0 above.
+:: On Windows 8 and newer, this issue has not been observed. It is possible that this
+:: issue is related to the above python bug, but this has not been conclusively confirmed,
+:: so using a separate env. var EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG to enable the known
+:: workaround this issue, which is to explicitly quit the calling process with the previous
+:: errorlevel from the above command.
+
+:: Also must use goto to jump to the command dispatch, since we cannot invoke emcc from
+:: inside a if() block, because if a cmdline param would contain a char '(' or ')', that
+:: would throw off the parsing of the cmdline arg.
+@if "%EM_WORKAROUND_PYTHON_BUG_34780%"=="" (
+  @if "%EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG%"=="" (
+    goto NORMAL
+  ) else (
+    goto NORMAL_EXIT
+  )
+) else (
+  @if "%EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG%"=="" (
+    goto MUTE_STDIN
+  ) else (
+    goto MUTE_STDIN_EXIT
+  )
+)
+
+:NORMAL_EXIT
+@%CMD% %*
+@exit %ERRORLEVEL%
+
+:MUTE_STDIN
+@%CMD% %* < NUL
+@exit /b %ERRORLEVEL%
+
+:MUTE_STDIN_EXIT
+@%CMD% %* < NUL
+@exit %ERRORLEVEL%
+
+:NORMAL
 @%CMD% %*

emcmake.bat

@@ -5,10 +5,56 @@
 :: To make modifications to this file, edit `tools/run_python.bat` and then run
 :: `tools/create_entry_points.py`
 
+:: All env. vars specified in this file are to be local only to this script.
 @setlocal
+
 @set EM_PY=%EMSDK_PYTHON%
 @if "%EM_PY%"=="" (
   set EM_PY=python
 )
 
+:: Python Windows bug https://bugs.python.org/issue34780: If this script was invoked via a
+:: shared stdin handle from the parent process, and that parent process stdin handle is in
+:: a certain state, running python.exe might hang here. To work around this, if
+:: EM_WORKAROUND_PYTHON_BUG_34780 is defined, invoke python with '< NUL' stdin to avoid
+:: sharing the parent's stdin handle to it, avoiding the hang.
+
+:: On Windows 7, the compiler batch scripts are observed to exit with a non-zero errorlevel,
+:: even when the python executable above did succeed and quit with errorlevel 0 above.
+:: On Windows 8 and newer, this issue has not been observed. It is possible that this
+:: issue is related to the above python bug, but this has not been conclusively confirmed,
+:: so using a separate env. var EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG to enable the known
+:: workaround this issue, which is to explicitly quit the calling process with the previous
+:: errorlevel from the above command.
+
+:: Also must use goto to jump to the command dispatch, since we cannot invoke emcc from
+:: inside a if() block, because if a cmdline param would contain a char '(' or ')', that
+:: would throw off the parsing of the cmdline arg.
+@if "%EM_WORKAROUND_PYTHON_BUG_34780%"=="" (
+  @if "%EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG%"=="" (
+    goto NORMAL
+  ) else (
+    goto NORMAL_EXIT
+  )
+) else (
+  @if "%EM_WORKAROUND_WIN7_BAD_ERRORLEVEL_BUG%"=="" (
+    goto MUTE_STDIN
+  ) else (
+    goto MUTE_STDIN_EXIT
+  )
+)
+
+:NORMAL_EXIT
+@"%EM_PY%" "%~dp0\%~n0.py" %*
+@exit %ERRORLEVEL%
+
+:MUTE_STDIN
+@"%EM_PY%" "%~dp0\%~n0.py" %* < NUL
+@exit /b %ERRORLEVEL%
+
+:MUTE_STDIN_EXIT
+@"%EM_PY%" "%~dp0\%~n0.py" %* < NUL
+@exit %ERRORLEVEL%
+
+:NORMAL
 @"%EM_PY%" "%~dp0\%~n0.py" %*