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Date: Thu, 18 Feb 2010 18:55:36 +0100
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Subject: CreateProcess() - executed program gets different argument depending  	if it's compiled with gcc (cygwin) or cl (VS)?
From: Piotr Krukowiecki <piotr DOT krukowiecki DOT news AT gmail DOT com>
To: cygwin AT cygwin DOT com
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Hello,

In short, I have a problem with passing "\\127.0.0.127\foo.cxx"
argument to a called program:

- if the executed program is compiled with cygwin's gcc the program
receives \127.0.0.127\foo.cxx (just one backslash at the begining).
- if it's compiled with cl it gets \\127.0.0.127\foo.cxx (double
backslash - what I expected)

I suspect cygwin incorrectly mangles backslashes in this case - or
maybe I'm quoting it incorrectly, or it is Windows fault?


Details:

I have a short program (source code for all programs attached at the
end) that just prints it's argv on standard output. I compile this
program twice: once with gcc from cygwin and once with VS cl.
I have another small program that executes those two programs using
CreateProcessA() and passes the same argument to them. Yet the
programs show unexpected difference (ignoring the acceptable
difference in argv[0]). Please see the log:

-------------
$ cl dumpargs.c /Fedumpargs_cl.exe
[...]
$ gcc -Wall dumpargs.c -o dumpargs_gcc.exe
$ gcc -Wall -o createprocess.exe createprocess.c
$ ./createprocess.exe

Command: F:\t\dumpargs_gcc.exe  "\\127.0.0.127\foo.cxx"
/cygdrive/f/t/dumpargs_gcc
\127.0.0.127\foo.cxx

Command: F:\t\dumpargs_cl.exe  "\\127.0.0.127\foo.cxx"
F:\t\dumpargs_cl.exe
\\127.0.0.127\foo.cxx
-------------

As you can see dumpargs_gcc receives "\127.0.0.127\foo.cxx" and
dumpargs_cl receives "\\127.0.0.127\foo.cxx".

In my opinion, based on "Parsing C++ Command-Line Arguments"
(http://msdn.microsoft.com/en-us/library/17w5ykft%28VS.100%29.aspx),
the cl version is correct.

Could you please explain if this is cygwin/microsoft or my bug?


Below I'm pasting source code for the createprocess and dumpargs program:

--- cut --- dumpargs.c --- cut ---
#include <stdio.h>
int main(int argc, char **argv) {
    int i;
    for (i = 0; i < argc; ++i) {
        printf("%s\n", argv[i]);
    }
    return 0;
}
--- cut --- cut --- cut ---

--- cut --- createprocess.c --- cut ---
#include <windows.h>
#include <stdio.h>
void runCommand(char * command) {
    STARTUPINFO si;
    PROCESS_INFORMATION pi;

    ZeroMemory(&pi, sizeof(pi));
    ZeroMemory(&si, sizeof(si));
    si.cb = sizeof(si);

    printf("\nCommand: %s\n", command);

    CreateProcessA(NULL, command, NULL, NULL, TRUE, 0, NULL, NULL, &si, &pi);
    WaitForSingleObject(pi.hProcess, INFINITE);

    CloseHandle( pi.hProcess );
    CloseHandle( pi.hThread );
}
#define COMMAND_ARGS " \"\\\\127.0.0.127\\foo.cxx\" "
int main() {
    runCommand("F:\\t\\dumpargs_gcc.exe " COMMAND_ARGS);
    runCommand("F:\\t\\dumpargs_cl.exe " COMMAND_ARGS);
    return 0;
}
--------------------------------------------



-- 
Piotr Krukowiecki

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