p5pRT
commented
10 years ago From @bulk88
Created by @bulk88
While investigating why re/subst.t and other subst*.t tests take 300 seconds on Win32 while their watchdog process times out\, (which is because the kill() in the end block is on cmd.exe's PID\, not the watchdog perl's PID\, killing the cmd.exe leaves watchdog perl process around\, which blocks harness script until the timeout at as high as 300 seconds expires\, why harness blocks on the watchdog proc IDK\, and that is for another ticket\, if appropriate) and other watchdog() from test.pl using .ts. TonyC brought up the question of why system() made a cmd.exe process when perl is not a shell builtin and should have been directly launched by the parent perl process (a perl that called watchdog()). I will investigate that in this ticket. This ticket isn't directly about the watchdog() bug\, it is about system()'s behavior. Fixing system() will probably fix the watchdog bug (there are other ways too\, like investigating why harness process hangs on the watchdog\, and switching test.pl to a process group kill() instead of single process kill()\, process group kill on Win32 was broken in 5.17 and is another ticket at https://rt-archive.perl.org/perl5/Ticket/Display.html?id=121230).
For testing my script is ------------------------------------------------------ system( 1\, 'C:\\perl519\\src\\t\\perl.exe "-I../lib" -e "sleep(300);warn qq/# Tes t process timed out - terminating\\n/;kill(KILL\, 12748);" '); ----------------------------------------------------- I am not sure why the "\\" are there even though its single quote. Data::Dumper printed it that way. PID 12748 doesn't exist on my system but it doesn't matter.
The callstack on blead generally looks like -------------------------------------------------------
perl519.dll!do_spawnvp_handles(int mode=1\, const char * cmdname=0x0090c5ec\, const char * const * argv=0x008f5614\, const int * handles=0x00000000) Line 3705 C perl519.dll!win32_spawnvp(int mode=1\, const char * cmdname=0x0090c5ec\, const char * const * argv=0x008f5614) Line 3698 + 0x13 C perl519.dll!Perl_do_aspawn(interpreter * my_perl=0x003645ec\, sv * really=0x00000000\, sv * * mark=0x0036aec8\, sv * * sp=0x0036aec4) Line 644 + 0x5b C perl519.dll!Perl_pp_system(interpreter * my_perl=0x003645ec) Line 4225 + 0x13 C perl519.dll!Perl_runops_debug(interpreter * my_perl=0x003645ec) Line 2420 + 0xd C perl519.dll!S_run_body(interpreter * my_perl=0x003645ec\, long oldscope=1) Line 2446 + 0xd C perl519.dll!perl_run(interpreter * my_perl=0x003645ec) Line 2365 C perl519.dll!RunPerl(int argc=2\, char * * argv=0x00362478\, char * * env=0x003629e0) Line 270 + 0x9 C++ perl.exe!main(int argc=2\, char * * argv=0x00362478\, char * * env=0x00362d58) Line 23 + 0x12 C perl.exe!mainCRTStartup() Line 398 + 0xe C kernel32.dll!_BaseProcessStart@4() + 0x23 --------------------------------------------------------- win32_spawnvp is a wrapper that has no logic of its own nowadays so I will ignore it exists. On the 1st try in do_spawnvp_handles CreateProcess is given "C:\perl519\src\t\perl.exe -I../lib -e sleep(300);warn qq/# Test process timed out - terminating\n/;kill(KILL\, 3824);" (no outer quotes) as cname/LPCTSTR lpApplicationName\, also notice all `"`s were removed from inside the path by perl\, and "C:\perl519\src\t\perl.exe "-I../lib" -e "sleep(300);warn qq/# Test process timed out - terminating\n/;kill(KILL\, 3824);"" (no outer quotes) as cmd/LPTSTR lpCommandLine.
lpApplicationName's MS docs are ------------------------------------------------------ lpApplicationName [in] Pointer to a null-terminated string that specifies the module to execute. The specified module can be a Windows-based application. It can be some other type of module (for example\, MS-DOS or OS/2) if the appropriate subsystem is available on the local computer. The string can specify the full path and file name of the module to execute or it can specify a partial name. In the case of a partial name\, the function uses the current drive and current directory to complete the specification. The function will not use the search path. If the file name does not contain an extension\, .exe is assumed. Therefore\, if the file name extension is .com\, this parameter must include the .com extension. The lpApplicationName parameter can be NULL. In that case\, the module name must be the first white space-delimited token in the lpCommandLine string. If you are using a long file name that contains a space\, use quoted strings to indicate where the file name ends and the arguments begin; otherwise\, the file name is ambiguous. For example\, consider the string "c:\program files\sub dir\program name". This string can be interpreted in a number of ways. The system tries to interpret the possibilities in the following order: c:\program.exe files\sub dir\program name c:\program files\sub.exe dir\program name c:\program files\sub dir\program.exe name c:\program files\sub dir\program name.exe If the executable module is a 16-bit application\, lpApplicationName should be NULL\, and the string pointed to by lpCommandLine should specify the executable module as well as its arguments. To run a batch file\, you must start the command interpreter; set lpApplicationName to cmd.exe and set lpCommandLine to the name of the batch file. ------------------------------------------------------
Obviously c string "C:\perl519\src\t\perl.exe -I../lib -e sleep(300);warn qq/# Test process timed out - terminating\n/;kill(KILL\, 3824);" is not a file. The 1st CreateProcess fails with GLR == 3/ERROR_PATH_NOT_FOUND. This is a reasonable error. Then do_spawnvp_handles() calls qualified_path() is called on this bogus file path. GetFileAttributes is called on file "C:\perl519\src\t\perl.exe -I../lib -e sleep(300);warn qq/# Test process timed out - terminating\n/;kill(KILL\, 3824); .exe"\, notice the new ".exe" at the end. GetFileAttributes fails with GLR == 3/ERROR_PATH_NOT_FOUND. Then GetFileAttributes is called with "C:\perl519\src\t\perl.exe -I../lib -e sleep(300);warn qq/# Test process timed out - terminating\n/;kill(KILL\, 3824);". Another bogus file. qualified_path() fails by returning NULL at this point. Then in do_spawnvp_handles\, the following executes ------------------------------- errno = ENOENT; ret = -1; goto RETVAL; ------------------------ And control returns to Perl_do_aspawn in win32.c\, do_aspawn then adds cmd.exe to argv array and then calls do_spawnvp_handles again with "cmd.exe" as cmdname instead of a bogus command line string. This works. But the child proc is now wrapped in a cmd.exe process. system()'s docs say ---------------------------------------- Does exactly the same thing as exec LIST \, except that a fork is done first and the parent process waits for the child process to exit. Note that argument processing varies depending on the number of arguments. If there is more than one argument in LIST\, or if LIST is an array with more than one value\, starts the program given by the first element of the list with arguments given by the rest of the list. If there is only one scalar argument\, the argument is checked for shell metacharacters\, and if there are any\, the entire argument is passed to the system's command shell for parsing (this is /bin/sh -c on Unix platforms\, but varies on other platforms). If there are no shell metacharacters in the argument\, it is split into words and passed directly to execvp \, which is more efficient. ---------------------------------------- The 2 parts that I dont fully understand is âthe argument is checked for shell metacharactersâ and âif there are no shell metacharacters in the argumentâ. We have a complete command line. The file path name might being with a â or not. The file path name might have a space in it\, and use â to group it into a file name. IDK what this code does Unix. There is a Perl_do_exec3 which defines âcheck for shell metacharactersâ but I dont think it is used on Windows. IDK what system() should be doing\, TonyC says it should not be calling cmd.exe/the shell. The docs say 1 arg list to system() is always a shell. Win32 Perl uselessly trys to launch the process without shell currently\, which needs to be stopped. Either Win32 Perl always uses shell/cmd.exe for 1 item system(). Or Perl knows how to pull out the file path name from the string and pass that to CreateProcess. IDK which it should be.
toddr
Migrated from rt.perl.org#121283 (status was 'open')
Searchable as RT121283$