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Date: Fri, 1 Aug 2025 22:42:36 +0900
To: cygwin AT cygwin DOT com
Subject: Re: Incorrect command line handling when launching Cygwin program
 from Windows
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From: Takashi Yano via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
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On Thu, 31 Jul 2025 13:28:14 +0000
"Old, Oliver via Cygwin" <cygwin AT cygwin DOT com> wrote:
> Hello!
> 
> I have recently noticed that the Windows command line parsing routine of Cygwin programs does not
> work correctly when an escaped quotation mark is included. This is relevant when launching a Cygwin-
> based GCC through Windows CMake-generated Ninja files. We are passing preprocessor definitions
> containing quotation marks to GCC and CMake wants to pass them backslash-escaped, but unquoted, on
> the command line.
> 
> A test program I have written to inspect this issue:
> 
> #include <stdio.h>
> int main(int argc, char** argv) {
>   for (int i = 0; i < argc; ++i) puts(argv[i]);
> }
> 
> Running it (via cmd.exe):
> 
> >echo.exe a b\"c\" d
> echo
> a
> b\c" d
> 
> The first escape sequence is ignored, but the quote is read and causes the parser to switch to
> quoted argument mode where it recognizes the remaining escaped quotes as it already should have done
> in regular parsing mode. It then proceeds to eat the remaining command line as there aren't any
> unescaped quotation marks, usually leading GCC to complain about no input files being given.
> 
> Running the Windows-native version of the program:
> 
> >echo-win32.exe a b\"c\" d
> echo-win32.exe
> a
> b"c"
> d
> 
> This should be the expected output. Is the way the escaped quotation mark is treated intended
> behavior? I cannot really see how it would be, given that the parser is only used for command lines
> stemming from being launched by Windows-native programs.

>echo-win32.exe C:\"Program Files"\
echo-win32.exe
C:"Program
Files\

Is this as you expected?

>echo.exe C:\"Program Files"\
echo
C:\Program Files\

This makes more sense to me.

-- 
Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>

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