tree 29a5b3825e66d608c2f40408a318a48a38a1ef95
parent 32894f4f111d07a216645eedc7c343431a7847bb
author Sam Lantinga <slouken@libsdl.org> 1564589480 -0700
committer Sam Lantinga <slouken@libsdl.org> 1564589480 -0700

Fixed bug 4692 - Command line parsing

Galadrim

As I have seen, SDL implements its own command line parser for Windows in SDL_windows_main.c. Unfortunately, it doesn't seem to allow command line arguments with trailing backslashes if quoting is required.

Usually, when you write an application that gets command line arguments passed as argc and argv, the parsing is done by parse_cmdline. The Windows API also provides the function CommandLineToArgvW, so an application can parse itself if only the command line string is provided. Both functions behave almost identically according to their documentation. If the argument "\\" (including the quotes) is passed, they both turn it into a single backslash.

The SDL command line parser on the other hand doesn't recognize the second quote character as the closing character in this example and therefore includes it in the parsed argument. The parser does not count the number of backslashes preceding a quote. It always treats a quote as escaped if a backslash is in front of it. Therefore, it should be impossible to quote and escape an argument correctly, if it has a trailing backslash and contains characters that require quoting.

Of course, each application is allowed to implement its own parsing rules, so SDL is free to do so. But the problem I see is that there are arguments, that are impossible to be passed to the parser correctly, as I described above. Is there a reason, why SDL does not simply use CommandLineToArgvW instead of implementing its own parser?

Here are some links that show that correct argument parsing, as it is usually done in Windows, is quite complicated:

https://docs.microsoft.com/en-us/windows/desktop/api/shellapi/nf-shellapi-commandlinetoargvw

http://www.windowsinspired.com/how-a-windows-programs-splits-its-command-line-into-individual-arguments/