For the past few days, I’ve been working on a small Protobuf Compiler plugin. During the course of development, I was stuck on a trivial yet annoying problem – path expansion.

This trivial problem led me to a wild goose chase. From branch diff’ing to debugging, it took me several days to figure this out.

Long Story Short

Here’s a small program called wildcard_input.

#include

int main(int argc, char **argv)
{
	for(int i=0; i<argc; ++i)
	{
		std::cout << argv[i] << std::endl;
	}
	return 0;
}

Now I invoke the following command.

wildcard_input *

This is the output from Win7 and Ubuntu 12.4.

Running from Window 7

Running from Ubuntu 12.04

Apparently path expansion is performed through the shell by default under Linux, whereas it is left to the program to handle under Windows. I prefer the Linux behavior, but others might disagree.

Windows Path Expansion

To get the automatic path expansion behavior in Windows, you need to add a linker options – /link setargv.obj in Visual Studio.

With this option, wildcard paths are now expanded properly.

Same program, compiled with the new linker option /link setargv.obj

Retrospection

1. Filed misleading bug to the Protobuf team.
2. Diff’ed 4 different branches for code delta
3. Hours of proto compiler debugging and Stackoverflow browsing.

… Alan