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C/C++

Expanding wildcard arguments

For making your program accept wildcard arguments, the official MSVC way is to link [w]setargv.obj to your program. By default it is not enabled. For more details see https://learn.microsoft.com/en-us/cpp/c-language/expanding-wildcard-arguments

Note that enabling wildcard expansion can have usability and security implications:

  • The program might transform the arguments you passed in, depending on the current directory, leading to user confusion.
  • The program might leak information about the existence and names of files on the filesystem.
  • Input validation might be bypassed if wildcard expansions is not taken into account.

With mingw-w64, there are three ways wildcard expansion can be configured:

  1. You can set _dowildcard in your source code to either 0 or -1 to disable or enable wildcard expansion.

    // To force-enable wildcard expansion
int _dowildcard = -1;
// To force-disable wildcard expansion
int _dowildcard = 0;

  2. You can link in CRT_noglob.o or CRT_glob.o to disable or enable wildcard expansion, respectively. This will error out if _dowildcard is already set in the source.

    # To force-enable wildcard expansion
cc main.c "$(cc -print-file-name=CRT_glob.o)"
# To force-disable wildcard expansion
cc main.c "$(cc -print-file-name=CRT_noglob.o)"

  3. mingw-w64 can be configured at build time to either enable or disable wildcard expansion by default via the --enable-wildcard configure flags. This can to be overridden on a per .exe basis by the user.

    Wildcard expansion is disabled by default in MSYS2.

Changelog

  • Starting with 2024-11-03 we have changed mingw-w64 to to disable wildcard handling by default. You can still enable it on a per application basis as described above. For more info on the change see the news entry.