C++ argument parsing is incorrect when the executable file path contains spaces

Question

I am having problems with arguments in C++ console programs built under C++Builder 12 Community Edition.

If the executable is in a folder with spaces in its name, eg. "test dir", and I invoke it from a console session in a DIFFERENT folder, then the arguments extracted by my code are incorrect. If the executable file path has no spaces, everything works fine. If I run it within the IDE, it's OK, too. Code built under Visual Studio 22 also works OK.

CPPtest.cpp

#include <iostream.h>

int main(int argc, char* argv[])
{
    cout << "argc: " << argc << "\n"; 
    cout << "argv0: " << argv[0] << "\n"; 
    cout << "argv1: " << argv[1] ; 
    return 0 ;`
}

The executable is located in a directory named "Misc projects", CWD is "C:\Junk":

C:\Junk>C:\"Misc projects"\CPPtest 3 8
argc: 2 ## INCORRECT: Should be 3
argv0: c:\Misc projects\CPPtest.exe
argv1: projects\CPPtest 3 8 # INCORRECT should be 8

Identical code when ran inside Visual Studio 22 performs correctly.

@AhmedAEK The console has absolutely nothing to do with it. Windows programs parse their own arguments, and should be using CommandLineToArgvW to do so. — Dúthomhas
– Dúthomhas, Commented Mar 29 at 10:03
The problem stems from a combination of partial path quoting and unescaped directory separators in the path string. @Dúthomhas is correct, though, don't rely on argc's default parsing behavior ,which is good for little more POC-stage usage. — Stelio Kontos
– Stelio Kontos, Commented Mar 29 at 10:35
FWIW: C++Builder has ParamCount() and ParamStr() functions that you can use instead of argc/argv. Internally, they parse the result of GetCommandLineW(). — Remy Lebeau
– Remy Lebeau, Commented Mar 29 at 19:15
On a side note: you should be using #include <iostream> instead of #include <iostream.h> — Remy Lebeau
– Remy Lebeau, Commented Mar 29 at 19:15

Stelio Kontos · Accepted Answer · 2025-03-31 12:07:37Z

11

You're quoting the file path incorrectly. Since you aren't escaping the directory separators in your path, the entire file path should be quoted, not just the portion with the space in it.

$ cd C:\Junk
$ "C:\Misc projects\CPPtest" 3 8

The program is executing, but the argument parsing's default behavior, which splits based on spaces, results in the following literal strings:

arg0: C:"Misc
arg1: projects"\CPPtest 3 8

The first quote is being inadvertently escaped by your unescaped directory separator (\"), and no longer counts as a quote. The second quote (which is literally your first and only quote now) is unclosed, meaning everything following it is treated as a single quoted string. Therefore, the first space is causing a first split, and the remaining spaces are ignored due to the " that isn't closed. This is one reason Windows path separators are escaped \\.

As for the behavior differing based on execution context:

When invoking the app from the same directory as the executable, most likely the full path is being omitted when you run it, thus removing the entire escape/quote/spaces issue altogether:

# cwd is "C:\Misc projects"
$ CPPtest 3 8
# argv = ["CPPTest", "3", "8"]

When debugging through VS, the executables file path is escaped properly as part of the debug launch task, so the file path is of no consequence.

In my experience with C# CLI programming, the executable name is actually excluded entirely from the program arguments, when running in the context of the debugger.

edited Mar 31 at 12:07

answered Mar 29 at 10:06

Stelio Kontos

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2 Comments

Jesper Juhl Mar 29 at 11:27

You probably also want to mention learn.microsoft.com/en-us/windows/win32/api/shellapi/…

Stelio Kontos Mar 30 at 21:02

@JesperJuhl props for that, updated answer with citation.

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